This report updates the previously published summary o f recommendations for vaccinating health-care personnel (HCP) in the United States (CDC. Immunization o f health-care workers: recommendations o f the Advisory Committee on Immunization Practices   and the Hospital Infection Control Practices Advisory Committee . M M W R 1997;46[No. RR-18J). This report was reviewed by and includes input from the Healthcare (formerly Hospital) Infection Control Practices Advisory Committee. These updated recommendations can assist hospital administrators, infection-controlpractitioners, employee health clinicians, and HCP in optimizing infection prevention and control programs. The recommendations for vaccinating HCP are presented by disease in two categories: 1) those diseases for which vaccination or documentation o f immunity is recommended because o f risks to HCP in their work settings for acquiring disease or transmitting to patients and 2) those for which vaccination might be indicated in certain circumstances. Background information for each vaccine-preventable disease and specific recommendations for use ofeach vaccine are presented. Certain infection-control measures that relate to vaccination also are included in this report. In addition, ACIP recommendations for the remaining vaccines that are recommended for certain or all adults are summarized, as are considerations for catch-up and travel vaccinations and for work restrictions. This report summarizes all current ACIP recommendations for vaccination o f HCP and does not contain any new recommendations or policies.# Immunization of Health-Care Personnel

# Recom m endations of the A dvisory Committee on Im m unization Practices (ACIP)
This report updates the previously published summary o f recom m endations o f the A dvisory C om m ittee on Immunization Practices (ACIP) and the Healthcare (formerly Hospital) Infection Control Practices Advisory Committee (HICPAC) for vaccinating health-care personnel (HCP) in the United States (1). The report, which was reviewed by and includes input from HICPAC, summarizes all current ACIP recommendations for vaccination of H C P and does not contain any new recommendations or policies that have not been published previously. These recommendations can assist hospital administrators, infection-control practitioners, employee health clinicians, and H C P in optimizing infection prevention and control programs.
H C P are defined as all paid and unpaid persons working in health-care settings who have the potential for exposure to patients and/or to infectious materials, including body substances, contaminated medical supplies and equipment, contaminated environmental surfaces, or contaminated air. H C P might include (but are not lim ited to) physicians, nurses, nursing assistants, therapists, technicians, emergency medical service personnel, dental personnel, pharmacists, laboratory personnel, autopsy personnel, students and trainees, contractual staff not employed by the health-care facility, and persons (e.g., clerical, dietary, housekeeping, laundry, security, maintenance, administrative, billing, and volunteers) not directly involved in patient care but potentially exposed to infectious agents that can be transmitted to and from HCP and patients (2).
Because of their contact with patients or infective material from patients, many HCP are at risk for exposure to (and possible transmission of) vaccine-preventable diseases. Employers and Introduction vaccination records for H C P so records can be retrieved easily as needed (3). Each record should reflect im m unity status for indicated vaccine-preventable diseases (i.e., documented disease, vaccination history, or serology results) as well as vaccinations adm inistered during em ploym ent and any documented episodes of adverse events after vaccination (4).
For each vaccine, the record should include date of vaccine administration (including for those vaccines that might have been received prior to employment), vaccine manufacturer and lot number, edition and distribution date of the languageappropriate Vaccine Information Statement (VIS) provided to the vaccinee at the time of vaccination, and the name, address, and title of the person administering the vaccine (4). Accurate vaccination records can help to rapidly identify susceptible H C P (i.e., those with no history of vaccination or lack of documentation of immunity) during an outbreak situation and can help reduce costs and disruptions to health care operations (5)(6)(7). H C P should be provided a copy of their vaccination records and encouraged to keep it with their personal health records so they can readily be made available to future employers. HICPAC has encouraged any facility or organization that provides direct patient care to formulate a comprehensive vaccination policy for all HCP (3). The American Hospital Association has endorsed the concept of vaccination programs for both hospital personnel and patients (8). To ensure that all H C P are up to date with respect to recommended vaccines, facilities should review H C P vaccination and immunity status at the time ofhire and on a regular basis (i.e., at least annually) with consideration of offering needed vaccines, if necessary, in conjunction with routine annual disease-prevention measures (e.g., influenza vaccination or tuberculin testing). These recommendations (Tables 2 and 3) should be considered during policy development. Several states and health-care facilities have established requirements relating to assessment of vaccination status and/or administration of one or more vaccines for H C P (9,10). Disease-specific outbreak control measures are described in this report and elsewhere (3,11,12). All HCP should adhere to all other recommended infectioncontrol guidelines, whether or not they are individually determined to have immunity to a vaccine-preventable disease.

# Methods
In 2008, the ACIP Immunization of Health-Care Personnel Work Group (the W ork Group) was formed as a subgroup of the ACIP Adult Immunization W ork Group to update the previously published recommendations for im m unization of HCP. The W ork Group comprised professionals from academic medicine (pediatrics, family medicine, internal medicine, occupational and environmental medicine, and infectious disease); federal and state public health professionals; and liaisons from the Society for Healthcare Epidemiology of America and HICPAC. The W ork Group met monthly, developed an outline for the report, worked closely with subject matter experts at C D C (who developed, revised, and updated sections of the report), and provided subsequent critical review of the draft documents. The approach of the Work Group was to summarize previously published ACIP recommendations and not to m ake new recom m endations or policies; a comprehensive list of publications containing the various vaccine-specific recommendations is provided (Table 1). In February 2011, the updated report was presented to ACIP, which voted to approve it.
The recommendations for vaccination of HCP are presented below by disease in two categories: 1) those diseases for which routine vaccination or documentation of immunity is recommended for H C P because of risks to H C P in their work settings and, should H CP become infected, to the patients they serve and 2) those diseases for which vaccination of HCP might be indicated in certain circumstances. Vaccines recommended in the first category are hepatitis B, seasonal influenza, measles, mumps, and rubella, pertussis, and varicella vaccines. Vaccines in the second category are meningococcal, typhoid, and polio vaccines. Except for influenza, all of the diseases prevented by these vaccines are notifiable at the national level (13). Main changes from the 1997 ACIP recommendations have been summarized (Box).

# Diseases for W hich Vaccination Is
Recom m ended O n the basis of docum ented nosocomial transmission, H C P are considered to be at substantial risk for acquiring or transm itting hepatitis B, influenza, measles, mumps, rubella, pertussis, and varicella. Current recommendations for vaccination are provided below.

# Hepatitis B

# Background

# Epidemiology and Risk Factors
Hepatitis B is an infection caused by the hepatitis B virus (HBV), which is transm itted through percutaneous (i.e., breaks in the skin) or mucosal (i.e., direct contact with mucous membranes) exposure to infectious blood or body fluids. The virus is highly infectious; for nonimmune persons, disease transmission from a needlestick exposure is up to 100 times more likely for exposure to hepatitis B e antigen (HBeAg)-positive blood than to HIV-positive blood (14). HBV infection is a well recognized occupational risk for U.S. HCP and globally. The risk for HBV is associated with degree of contact with blood in the work place and with the hepatitis B e-antigen status of the source persons (15). The virus is also environmentally stable, remaining infectious on environmental surfaces for at least 7 days (16).
In 2009 in the United States, 3,371 cases of acute HBV infection were reported nationally, and an estimated 38,000 new cases of HBV infection occurred after accounting for underreporting and underdiagnosis (17). O f 4,519 persons reported with acute HBV infection in 2007, approximately 40% were hospitalized and 1.5% died (18). HBV can lead to chronic infection, which can result in cirrhosis of the liver, liver failure, liver cancer, and death. An estimated 800,000- 1.4 million persons in the United States are living with chronic HBV infection; these persons serve as the main reservoir for continued HBV transmission (19).
Vaccines to prevent hepatitis B became available in the United States in 1981; a decade later, a national strategy to eliminate HBV infection was implemented, and the routine vaccination of children was recommended (20). During 1990During 2009, the rate of new HBV infections declined approximately 84%, from 8.5 to 1.1 cases per 100,000 population (17); the decline was greatest (98%) among persons aged <19 years, for whom recommendations for routine infant and adolescent vaccination have been applied. Although hepatitis B vaccine coverage is high in infants, children, and adolescents (91.8% in infants aged 19-35 months and 91.6% in adolescents aged 13-17 years) (21,22), coverage remains lower (41.8% in 2009) for certain adult populations, including those with behavioral risks for HBV infection (e.g., men who have sex with men and persons who use injection drugs) (23).

# Hepatitis B in Health-Care Settings
During 1982, when hepatitis B vaccine was first recommended for HCP, an estimated 10,000 infections occurred among persons employed in a medical or dental field. By 2004, the number of HBV infections among HCP had decreased to an estimated 304 infections, largely resulting from the im plem entation of routine preexposure vaccination and improved infection-control precautions (24)(25)(26).
The risk for acquiring HBV infection from occupational exposures is dependent on the frequency of percutaneous and mucosal exposures to blood or body fluids (e.g., semen, saliva, and wound exudates) containing HBV, particularly fluids containing HBeAg (a marker for high HBV replication and viral load) (27)(28)(29)(30)(31). The risk is higher during the professional BOX. Summary of main changes- from 1997 Advisory Comm ittee on Immunization Practices/Hospital (now Healthcare) Infection Control Practices Advisory Comm ittee recommendations for immunization of health-care personnel (HCP)

# Hepatitis B
- H C P and trainees in certain populations at high risk for chronic hepatitis B (e.g., those born in countries with high and intermediate endemicity) should be tested for HBsAg and anti-HBc/anti-HBs to determine infection status.

# Influenza
- Emphasis that all HCP, not just those with direct patient care duties, should receive an annual influenza vaccination - Comprehensive programs to increase vaccine coverage among H C P are needed; influenza vaccination rates among HCP within facilities should be measured and reported regularly. Measles, mumps, and rubella (MMR) - History of disease is no longer considered adequate presumptive evidence of measles or mumps immunity for HCP; laboratory confirmation of disease was added as acceptable presumptive evidence of immunity. History of disease has never been considered adequate evidence of immunity for rubella. - The footnotes have been changed regarding the recommendations for personnel born before 1957 in routine and outbreak contexts. Specifically, guidance is provided for 2 doses of M M R for measles and mumps protection and 1 dose of M M R for rubella protection. Pertussis - HCP, regardless of age, should receive a single dose of Tdap as soon as feasible if they have not previously received Tdap.
- The minimal interval was removed, and Tdap can now be administered regardless of interval since the last tetanus or diphtheria-containing vaccine. - Hospitals and ambulatory-care facilities should provide Tdap for HCP and use approaches that maximize vaccination rates. Varicella Criteria for evidence of immunity to varicella were established. For H C P they include - written documentation with 2 doses of vaccine, - laboratory evidence of immunity or laboratory confirmation of disease, - diagnosis of history of varicella disease by health-care provider, or diagnosis of history of herpes zoster by health-care provider.

# Meningococcal
- H C P with anatomic or functional asplenia or persistent complement component deficiencies should now receive a 2-dose series of meningococcal conjugate vaccine. H C P with H IV infection who are vaccinated should also receive a 2 dose series. - Those HCP who remain in groups at high risk are recommended to be revaccinated every 5 years.
Abbreviations: HBsAg = Hepatitis B surface antigen; anti-HBc = hepatitis B core antibody; anti-HBs = hepatitis B surface antibody; Tdap = tetanus toxoid, reduced diptheria toxoid and acellular pertussis vaccine; HIV = human immunodeficiency virus. training period and can vary throughout a person's career (1). Depending on the tasks performed, health-care or public safety personnel m ight be at risk for HBV exposure; in addition, personnel providing care and assistance to persons in outpatient settings and those residing in long-term-care facilities (e.g., assisted living) might be at risk for acquiring or facilitating transmission of HBV infection when they perform procedures that expose them to blood (e.g., assisted bloodglucose monitoring and wound care) (32)(33)(34).
A Federal Standard issued in D ecem ber 1991 under the O ccupational Safety and H ealth Act m andates that hepatitis B vaccine be made available at the employer's expense to all health-care personnel who are exposed occupationally to blood or other potentially infectious materials (35). The Federal Standard defines occupational exposure as reasonably anticipated skin, eye, m ucous m em brane, or parenteral contact with blood or other potentially infectious materials that might result from the performance of an employee's duties (35

# Vaccine Effectiveness
The 3-dose vaccine series administered intramuscularly at 0, 1, and 6 months produces a protective antibody response in approximately 30% -55% of healthy adults aged 90% after the third dose (40)(41)(42). After age 40 years, <90% of persons vaccinated with 3 doses have a protective antibody response, and by age 60 years, protective levels of antibody develop in approximately 75% of vaccinated persons (43). Smoking, obesity, genetic factors, and immune suppression also are associated with dim inished im m une response to hepatitis B vaccination (43-46).

# Duration of Immunity
Protection against symptomatic and chronic HBV infection has been docum ented to persist for >22 years in vaccine responders (47). Im m unocom petent persons who achieve hepatitis B surface antibody (anti-HBs) concentrations of >10 mIU/mL after preexposure vaccination have protection against both acute disease and chronic infection. Anti-HBs levels decline over time. Regardless, responders continue to be protected, and the majority of responders will show an anamnestic response to vaccine challenge (47)(48)(49)(50)(51). Declines might be somewhat faster among persons vaccinated as infants rather than as older children, adolescents, or adults and among those administered recombinant vaccine instead of plasma vaccine (which has not been commercially available in the United States since the late 1980s). Although immunogenicity is lower among immunocompromised persons, those who achieve and maintain a protective antibody response before exposure to HBV have a high level of protection from infection (52).
Among persons who do not respond to a primary 3-dose vaccine series (i.e., those in whom anti-HBs concentrations of >10 mIU/mL were not achieved), 25% -50% respond to an additional vaccine dose, and 44% -100% respond to a 3-dose revaccination series using standard or high dosage vac cine (43,(53)(54)(55)(56)(57)(58). Persons who have measurable but low (i.e., 1-9 mIU/mL) levels of anti-HBs after the initial series have better response to revaccination than persons who have no anti-HBs (49,53,54). Persons who do not have protective levels of anti-HBs 1-2 months after revaccination either are infected with HBV or can be considered primary nonresponders; for the latter group, genetic factors might be associated with nonresponse to hepatitis B vaccination (54,58,59). ACIP does not recommend more than two vaccine series in nonresponders (52).

# Vaccine Safety
Hepatitis B vaccines have been demonstrated to be safe when administered to infants, children, adolescents, and adults (52,60,61). Although rare cases of arthritis or alopecia have been associated temporally with hepatitis B vaccination, recent data do not support a causal relationship between hepatitis B vaccine and either arthritis or alopecia (61)(62)(63). During 1982During 2004, an estimated 70 million adolescents and adults and 50 million infants and children in the United States received >1 dose of hepatitis B vaccine (52). The most frequently reported side effects in persons receiving hepatitis B vaccine are pain at the injection site (3% -29% ) and temperature of >99.9 F (>37.7 C) (1% -6% ) (64-67). However, in placebo-controlled studies, these side effects were reported no more frequently among persons receiving hepatitis B vaccine than among persons receiving placebo (40,41,(64)(65)(66)(67). Revaccination is not associated with an increase in adverse events. Hepatitis B vaccination is contraindicated for persons with a history of hypersensitivity to yeast or any vaccine component (4,(64)(65)(66). Persons with a history of serious adverse events (e.g., anaphylaxis) after receipt of hepatitis B vaccine should not receive additional doses. As with other vaccines, vaccination of persons with moderate or severe acute illness, with or without fever, should be deferred until illness resolves (4). Vaccination is not contraindicated in persons with a history of multiple sclerosis, Guillain-Barre Syndrome, autoim m une disease (e.g., systemic lupus erythematosis and rheumatoid arthritis), or other chronic diseases. Pregnancy is not a contraindication to vaccination; limited data suggest that developing fetuses are not at risk for adverse events when hepatitis B vaccine is administered to pregnant women (4,68). Available vaccines contain noninfectious hepatitis B surface antigen (HBsAg) and do not pose any risk for infection to the fetus.

# Postexposure
The need for postexposure prophylaxis should be evaluated immediately after H C P experience any percutaneous, ocular, m ucous-m em brane or nonintact skin exposure to blood or body fluid in the workplace. Decisions to administer postexposure prophylaxis should be based on the HBsAg status of the source and the vaccination history and vaccine-response status of the exposed H C P (Table 4) (72).

# Unvaccinated and Incompletely Vaccinated HCP and Trainees
- Unvaccinated or incompletely vaccinated persons who experience a workplace exposure from persons known to be HBsAg-positive should receive 1 dose of hepatitis B immune globulin HBIG (i.e., passive vaccination) as soon as possible after exposure (preferably within 24 hours).
The effectiveness of HBIG when administered >7 days after percutaneous or permucosal exposures is unknown (Table 4). - Hepatitis B vaccine should be administered in the deltoid muscle as soon as possible after exposure; HBIG should be administered at the same time at another injection site. The 3-dose hepatitis B vaccine series should be completed for previously unvaccinated and incompletely vaccinated persons who have needlestick or other percutaneous exposures, regardless of the HBsAg status of the source and w hether the status o f the source is known. To document protective levels of anti-HBs (>10mIU/mL), postvaccination testing of persons who received HBIG for postexposure prophylaxis should be performed after anti-HBs from HBIG is no longer detectable (4-6 months after administration).

# Vaccinated HCP and Trainees
- Vaccinated H C P with documented immunity (anti-HBs concentrations of >10 mIU/mL) require no postexposure prophylaxis, serologic testing, or additional vaccination. - Vaccinated H C P with docum ented nonresponse to a 3-dose vaccine series should receive 1 dose of HBIG and a second 3-dose vaccine series if the source is HBsAgpositive or known to be at high risk for carrying hepatitis.
If the source is known or determ ined to be HBsAgnegative, these previously nonresponding H C P should com p lete the rev accin atio n series and undergo postvaccination testing to ensure that their response status is docum ented ( Influenza causes an estim ated average of >200,000 hospitalizations and 3,000-49,000 deaths annually in the United States (74)(75)(76). The majority of influenza-related severe illnesses and deaths occur among persons with chronic medical conditions, infants and young children, seniors, and pregnant women (74)(75)(76)(77)(78). Reducing the risk for influenza among persons at higher risk for complications is a major focus of influenza prevention strategies (77).

# Influenza Transmission in Health-Care Settings
HCP are exposed to patients with influenza in the workplace and are thus at risk of occupationally acquired influenza and of transmitting influenza to patients and other HCP. In a cross sectional survey of hospital house staff (physicians in training), 37% reported influenza-like illness during September-April, and 9% reported more than one respiratory illness. Length of illness varied (range: 1-10 days; mean: 7 days), as did days of work missed (range: 0-10 days; mean: 0.7 days) (79). Infected HCP who continue to work while ill might transmit influenza to patients, many of whom are at increased risk for severe outcomes from influenza. H C P are therefore recommended for routine annual influenza vaccination (77).
Few randomized trials of the effect that influenza vaccination has on illness in H CP have been conducted. In one randomized trial of 427 HCP, influenza vaccination of H C P failed to decrease episodes of respiratory infection or duration of illness but was associated with a 28% decrease in absenteeism (from 1.4 days to 1.0 day) attributable to respiratory infections (80). No laboratory confirmation of influenza was obtained in this study. In another randomized trial among HCP, vaccination was associated with a significantly lower rate of serological evidence of influenza infection, with a vaccine efficacy rate of 88% for influenza A and 89% for influenza B (p<0.05) (81); however, no significant differences were noted in days of febrile respiratory illness or absenteeism.
Influenza can cause outbreaks of severe respiratory illness among hospitalized persons and long-term-care residents (82)(83)(84)(85)(86)(87)(88)(89)(90). Influenza outbreaks in hospitals (86)(87)(88) and long-termcare facilities (91) have been associated with low vaccination rates among HCP. One nonrandomized study demonstrated an increase in H C W vaccination rates and decrease in nosocomially acquired, laboratory-confirmed influenza in a hospital after a mobile cart-based H C P vaccination program was introduced (86). Several randomized controlled studies of the impact of H C P vaccination on morbidity and mortality in long-term care facilities have been performed (92)(93)(94)(95). These studies have demonstrated substantial decreases in all cause mortality (92)(93)(94)(95) and influenza-like illness (92,94,95). However, studies which examine and demonstrate efficacy in preventing more specific outcomes (e.g., laboratory-confirmed influenza illness and mortality) are lacking. Recent systematic reviews suggest that vaccination of HCP in settings in which patients also were vaccinated provided significant reductions in deaths among elderly patients from all causes and deaths from pneumonia, but also note that additional randomized controlled trials are warranted (96,97), as are examination of more specific outcomes.
Preventing influenza among HCP who might serve as sources of influenza virus transmission provides additional protection to patients at risk for influenza complications. Vaccination of H C P can specifically benefit patients who cannot receive vaccination (e.g., infants aged 85 years and immune-compromised persons), and persons for whom antiviral treatment is not available (e.g., persons with medical contraindications). Although annual vaccination has long been recommended for H C P and is a high priority for reducing morbidity associated with influenza in health-care settings (98)(99)(100), national survey data have demonstrated that the vaccination coverage level during the 2008-09 season was 52.9% (101).

# Considerations Regarding Influenza Vaccination of HCP
Barriers to H C P aceptance of influenza vaccination have included fear of vaccine side effects (particularly influenza like symptoms), insufficient time or inconvenience, perceived ineffectiveness of the vaccine, perceived low likelihood of contracting influenza, avoidance of medications, and fear of needles (79,(102)(103)(104)(105)(106)(107)(108)(109). Factors demonstrated to increase vaccine acceptance include a desire for self-protection, previous receipt of influenza vaccine, a desire to protect patients, and perceived effectiveness of vaccine (79,105,106,(109)(110)(111)(112). Strategies that have demonstrated improvement in H C P vaccination rates have included campaigns to emphasize the benefits of H C P vaccination for staff and patients, vaccination of senior medical staff or opinion leaders, removing administrative barriers (e.g., costs), providing vaccine in locations and at times easily accessible by HCP, and monitoring and reporting H C P influenza vaccination rates (99,(113)(114)(115)(116)(117)(118)(119)(120). Intranasally administered live attenuated influenza vaccine (LAIV) is an option for healthy, nonpregnant adults aged <50 years who dislike needles.
The practice of obtaining signed declinations from HCP offered influenza vaccination has been adopted by some institutions but has not yet been demonstrated to exceed coverage rates of >70% -80% (99,115,(121)(122)(123). Institutions that require declination statements from H C P who refuse influenza vaccination should educate and counsel these HCP about benefits of the vaccine.
Each health-care facility should develop a comprehensive influenza vaccination strategy that includes targeted education about the disease, including disease risk among H C P and patients, and about the vaccine. In addition, the program should establish easily accessible vaccination sites and inform H C P about their locations and schedule. Facilities that employ H C P should provide influenza vaccine at no cost to personnel (124). The most effective combination of approaches for achieving high influenza vaccination coverage among H C P likely varies by institution. Hospitals and health-care organizations in the United States traditionally have employed an immunization strategy that includes one or more of the following components: education about influenza, easy access to vaccine, incentives to encourage immunization, organized campaigns, institution of declination policies, and legislative and regulatory efforts (e.g., vaccination requirements) (99,115,(121)(122)(123)(124)(125)(126).
Beginning January 1, 2007, the Joint Comm ission on A ccreditation o f H ealth-C are O rganizations required accredited organizations to offer influenza vaccinations to staff, including volunteers and licensed independent practitioners and to report coverage levels among HCP (127). Standards are available for measuring vaccination coverage among HCP as a measure of program performance within a health care setting (128). Beginning January 2013, the Centers for Medicaid Services will require acute care hospitals to report HCP influenza vaccine as part of its hospital inpatient quality reporting program.*

# Vaccine Effectiveness, Duration of Immunity, and Vaccine Safety
Effectiveness of influenza vaccines varies from year to year and depends on the age and health status of the person getting the vaccine and the similarity or "match" between the viruses or virus in the vaccine and those in circulation. Vaccine strains are selected for inclusion in the influenza vaccine every year based on international surveillance and scientists' estimations about which types and strains of viruses will circulate in a given year. Annual vaccination is recommended because the predom inant circulating influenza viruses typically change from season to season and, because immunity declines over time postvaccination (77).
In placebo-controlled studies am ong adults, the most frequent side effect o f vaccination was soreness at the vaccination site (affecting 10% -64% of patients) that lasted <2 days (129,130). These injection-site reactions typically were mild and rarely interfered with the recipient's ability to conduct usual daily activities. The main contraindication to influenza vaccination is a history of anaphylactic hypersensitivity to egg or other components of the vaccine. A history of Guillain-Barre Syndrome within 6 weeks following a previous dose of influenza vaccine is considered to be a precaution for use of influenza vaccines (77

# Vaccination
Annual influenza vaccination is recommended for all persons aged >6 m onths who have no medical contraindication; therefore, vaccination of all HCP who have no contraindications is recommended. The influenza vaccine is evaluated annually with one or more vaccine strains updated almost every year. In addition, antibody titers decline during the year after vaccination. T hus, annual vaccination w ith the current season's formulation is recommended. Annual vaccination is appropriate and safe to begin as early in the season as vaccine is available. HCP should be among the groups considered for prioritized receipt of influenza vaccines when vaccine supply is limited.
Two types of influenza vaccines are available. LAIV is administered intranasally and is licensed for use in healthy nonpregnant persons aged 2-49 years. The trivalent inactivated vaccine (TIV) is administered as an intramuscular injection and can be given to any person aged >6 months. Both vaccine types contain vaccine virus strains that are selected to stimulate a protective immune response against the wild-type viruses that are thought to be most likely in circulation during the upcoming season. Use of LAIV for H C P who care for patients housed in protective inpatient environments has been a theoretic concern, but transmission of LAIV in health-care settings has not been reported. LAIV can be used for HCP who work in any setting, except those who care for severely immunocompromised hospitalized persons who require care in a protective environment. H C P who themselves have a condition that confers high risk for influenza complications, who are pregnant, or who are aged >50 years should not receive LAIV and should be administered TIV instead. An inactivated trivalent vaccine containing 60 mcg of hemagglutinin antigen per influenza vaccine virus strain (Fluzone High-Dose ) is an alternative inactivated vaccine for persons aged >65 years. Persons aged >65 years may be administered any of the standard-dose TIV preparations or Fluzone High-Dose (77). The majority of T IV preparations are administered intramuscularly. An intradermally administered T IV was licensed in May 2011 and is an alternative to other TIV preparations for persons aged 18-64 years (131).

# Use of Antiviral Drugs for Treating Exposed Persons and Controlling Outbreaks
Use of antiviral drugs for chemoprophylaxis or treatment of influenza is an adjunct to (but not a substitute for) vaccination. Oseltamivir or zanamivir are recommended currently for chemoprophylaxis or treatment of influenza (132,133). TIV Recommendations can be administered to exposed, unvaccinated H C P at the same time as chemoprophylaxis, but LAIV should be avoided because the antiviral medication will prevent viral replication needed to stimulate a vaccine response (77). Antivirals are used often among patients during outbreaks in closed settings such as long-term-care facilities but also can be administered to unvaccinated H C P during outbreaks, when an exposure to a person with influenza occurs, or after exposure when vaccination is not thought to be protective against the strain to which a vaccinated H C P was exposed. Chemoprophylaxis consists of 1 dose (of either antiviral drug) daily for 10 days, and treatment consists of 1 dose twice daily for 5 days. In many instances of H C P exposure, watchful waiting and early initiation of treatment if symptoms appear is preferred rather than use of antiviral chemoprophylaxis immediately after exposure. The intensity and duration of the exposure and the underlying health status of the exposed worker are important factors in clinical judgm ents about w hether to provide chemoprophylaxis. If chemoprophylaxis is used, the provider should base choice of the agent on whether the circulating strain or strains of influenza have demonstrated resistance to particular antivirals.

# Program Evaluation
- Health-care adm inistrators should include influenza vaccination coverage among H C P as a measure of quality of care (124). - Influenza vaccination rates among HCP within facilities should be regularly measured and reported, and ward-, unit-, and specialty-specific coverage rates should be provided to staff and adm inistration (124). Such information might be useful to promote compliance with vaccination policies.

# Measles

# Background

# Epidemiology and Risk Factors
Measles is a highly contagious rash illness that is transmitted by respiratory droplets and airborne spread. Severe complications, w hich m ight result in death, include pneum onia and encephalitis. Before the national measles vaccination program was im plem ented in 1963, almost every person acquired measles before adulthood; an estimated 3-4 million persons in the U nited States acquired measles each year (134). Approximately 500,000 persons were reported to have had measles annually, of whom 500 persons died, 48,000 were hospitalized, and another 1,000 had permanent brain damage from measles encephalitis (134).
Through a successful 2-dose measles vaccination program (i.e., a first dose at age 12-15 months and a second dose between ages 4 -6 years) (135) and better measles control throughout the region o f the Americas (136), endemic transmission of measles was interrupted in the United States, and measles was declared eliminated from the country in 2000 (137). However, measles remains widespread in the majority of countries outside the Western Hemisphere, with an estimated 20 m illion measles cases occurring worldwide (138) and approximately 164,000 related deaths (139). Thus, the United States continues to experience international importations that might lead to transmission among U.S. residents and limited outbreaks, especially in unvaccinated populations (140)(141)(142)(143).
During 2001-2008, a total of 557 confirmed measles cases were reported in the United States from 37 states and the District of Columbia (annual median: 56; range: 37 in 2004 to 140 in 2008), representing an annual incidence ofless than one case per million population (144). O fthe 557 reported case-patients, 126 (23%) were hospitalized (annual median: 16; range: 5-29); of these, at least five case-patients were admitted to intensive care. Two deaths were reported, both in 2003 (144).
O f the 557 reported case-patients during 2001-2008, a total of 223 (40%) were adults, including 156 (28%) aged 20-39 years and 67 (12%) aged >40 years. O f the 438 measles cases among U.S. residents, 285 (65%) cases were considered preventable (i.e., occurred among persons who were eligible for vaccination but were unvaccinated) (144). The remaining 153 (35%) cases were considered nonpreventable. Cases were defined as nonpreventable if they occurred among U.S. resident case-patients who had received >1 dose of measles-containing vaccine, if patients were vaccinated as recommended if traveling internationally, or if they were not vaccinated but had other evidence of im m unity (i.e., were born before 1957 and therefore presumed immune from natural disease in childhood, had laboratory evidence of immunity, or had documentation of physician-diagnosed disease) or for whom vaccination is not recommended. During 2001-2008, a total of 12.5% (one of eight) of measles cases reported to CD C among H C P occurred in persons born before 1957; the other seven cases occurred among H C P born after 1957.
Measles-mumps-rubella (MMR) vaccination policies have been enforced with variable success in United States health care facilities over the past decade. Even though medical settings were a primary site of measles transmission during the 1989-1991 measles resurgence (145,146), as of September 2011, only three states (New York, Oklahoma, and Rhode Island) had laws mandating that all hospital personnel have proof of measles immunity and did not allow for religious or philosophic exemptions (147).
Vaccine coverage in the United States is high; in 2010, a total of 91

# Measles Transmission and the Costs of Mitigating Measles Exposures in Health-Care Settings
Health-care-associated cases of measles are of public health concern. Because of the severity of measles, infected persons are likely to seek medical care in primary health-care facilities, emergency departments, or hospitals (141,149,150). Medical settings played a prominent role in perpetuating outbreaks of measles transmission during the 1989-1991 measles resurgence (145,146) and were a primary site of measles transmission in a health-care-associated outbreak in 2008 (149). During 2001 2008, a total of 27 reported measles cases were transmitted in U.S. health-care facilities, accounting for 5% of all reported U.S. measles cases.
Because of the greater opportunity for exposure, HCP are at higher risk than the general population for becoming infected with measles. A study conducted in 1996 in medical facilities in a county in Washington state indicated that HCP were 19 times more likely to develop measles than other adults (151). During 2001During -2008, in the 23 health-care settings in which measles transmission was reported, eight cases occurred among HCP, six (75%) of whom were unvaccinated or had unknown vaccination status. One health-care provider was hospitalized in an intensive care unit for 6 days from severe measles complications (142). During a health-care-associated measles outbreak in Arizona in 2008 with 14 cases, six cases were acquired in hospitals, and one was acquired in an outpatient setting. One unvaccinated health-care worker developed measles and infected a hospital emergency room patient who required intensive care following hospital admission for measles (149).
High costs also are involved in evaluating and containing exposures and outbreaks in health-care facilities, as well as a substantial disruption of regular hospital routines when control measures are instituted, especially if hospitals do not have readily available data on the measles immunity status of their staff and others included in the facility vaccination program. In 2005 in Indiana, one hospital spent more than $113,000 responding to a measles outbreak (142), and in 2008 in Arizona, two hospitals spent $799,136 responding to and containing cases in their facilities (149). The Arizona outbreak response required rapid review of measles documentation of 14,844 H C P at seven hospitals and emergency vaccination of approximately 4,500 H C P who lacked documentation of measles immunity. Serologic testing at two hospitals among 1,583 H C P without documented history of vaccination or without documented laboratory evidence of measles immunity revealed that 138 (9%) of these persons lacked measles IgG antibodies (149).

# Vaccine Effectiveness, Duration of Immunity and Seroprevalence Studies, and Vaccine Safety
Vaccine Effectiveness M M R vaccine is highly effective in preventing measles with a 1-dose vaccine effectiveness of 95% when administered on or after age 12 months and a 2-dose vaccine effectiveness of 99% (135).

# Duration of Immunity and Seroprevalence Studies
Two doses of live measles vaccine are considered to provide long-lasting immunity (135). Although antibody levels decline following vaccination, a study examining neutralizing antibody levels up to 10 years following the second dose of M M R vaccine in children indicates that antibodies remain above the level considered protective (152).
Studies among H C P in the United States during the measles resurgence in the late 1980s through early 1990s demonstrated that 4% -10% of all H C P lacked measles IgG antibodies (153)(154)(155)(156). During the 2008 Arizona outbreak, of the 1,077 health-care providers born during or after 1957 without documented measles immunity, 121 (11%) were seronegative (149). In a study of measles seroprevalence among 469 newly hired H C P at a hospital in N orth Carolina who were born before 1957, and thus considered immune by age, who could not provide written evidence of immunity to measles, serologic testing indicated that six (1.3%) lacked measles IgG antibodies (157). Other serologic studies of hospital-based H C P indicate that 2%-9% of those born before 1957 lacked antibodies to measles (156,(158)(159)(160).
A survey co n d u cted d u rin g 1999-2004 foun d a seroprevalence of measles antibodies of 95.9% among persons in the U.S. population aged 6-49 years (161). The survey indicated that the lowest prevalence, 92.4% , was among adults born during 1967-1976 (161). A 1999 study of U.S. residents aged >20 years determined that 93% had antibodies to measles virus (162).

# Vaccine Safety
Measles vaccine is administered in combination with the mumps and rubella components as the M M R vaccine in the United States. Monovalent measles vaccine rarely has been used in the United States in the past 2 decades and is no longer available. After decades of use, evidence demonstrates that M M R vaccine has an excellent safety profile (134).
T he m ajority of docum ented adverse events occur in children. In rare circumstances, M M R vaccination of adults has been associated w ith the following adverse events: anaphylaxis (approximately 1.0-3.5 occurrences per million doses administered) (134), thrombocytopenia from the measles component or rubella component (a rate of three to four cases for every 100,000 doses) ( 134), and acute arthritis from the rubella component (arthralgia develops among approximately 25% of rubella-susceptible postpubertal females after M M R vaccination, and approximately 10% have acute arthritis-like signs and symptoms) (135). W hen joint symptoms occur, they generally persist for 1 day-3 weeks and rarely recur (135). Chronic joint symptoms attributable to the rubella component of the M M R vaccine are reported very rarely, if they occur at all. Evidence does not support an association between M M R vaccination and any of the following: hearing loss, retinopathy, optic neuritis, Guillain-Barre Syndrome, type 1 diabetes, Crohn's disease, or autism (135,(163)(164)(165)(166)(167)(168)(169).
A woman can excrete the rubella vaccine virus in breast milk and transmit the virus to her infant, but the infection remains asymptomatic (135) Presumptive evidence of immunity to measles for persons who work in health-care facilities includes any of the following:
- written documentation of vaccination with 2 doses of live measles or M M R vaccine administered at least 28 days apart,'!' - laboratory evidence of immunity,  - laboratory confirmation of disease, or - birth before 1957.J

# Prevaccination Testing
Prevaccination antibody screening before M M R vaccination for an employee who does not have adequate presumptive evidence of im m unity is not necessary unless the medical facility considers it cost effective (134,(170)(171)(172) although no recent studies have been conducted. For H C P who have 2 documented doses of M M R vaccine or other acceptable evidence of immunity to measles, serologic testing for immunity is not recommended. In the event that a H C P who has 2 documented doses of M M R vaccine is tested serologically and determined to have negative or equivocal measles titer results, it is not recommended that the person receive an additional dose of M M R vaccine. Such persons should be considered to have presumptive evidence of measles immunity. Documented ageappropriate vaccination supersedes the results of subsequent serologic testing. Because rapid vaccination is necessary to halt disease transmission, during outbreaks of measles, serologic screening before vaccination is not recommended.

# Use of Vaccine and Immune Globulin for Treating Exposed Persons and Controlling Outbreaks
Following airborne infection-control precautions and implementing other infection-control measures are important to control the spread of measles but might fail to prevent all nosocomial transmission, because transmission to other susceptible persons might occur before illness is recognized. Persons infected with measles are infectious 4 days before rash onset through 4 days after rash onset. W hen a person who is suspected of having measles visits a health-care facility, airborne infection-control precautions should be followed stringently. The patient should be asked immediately to wear a medical mask and should be placed in an airborne-infection isolation room (i.e., a negative airpressure room) as soon as possible. If an airborne-infection isolation room is not available, the patient should be placed in a private room with the door closed and be asked to wear a mask. If possible, only staff with presumptive evidence of immunity should enter the room of a person with suspect or confirmed measles. Regardless of presumptive immunity status, all staff entering the room should use respiratory protection consistent with airborne infection-control precautions (i.e., use of an N95 respirator or a respirator with similar effectiveness in preventing airborne transmission) (3,150).
Because of the possibility, albeit low (~1%), of measles vaccine failure in H C P exposed to infected patients (173), all H C P should observe airborne precautions in caring for patients with measles. H C P in whom measles occurs should be excluded from work until >4 days following rash onset. Contacts w ith measles-compatible sym ptom s should be isolated, and appropriate infection-control measures (e.g., rapid vaccination of susceptible contacts) should be implemented to prevent further spread (174).
If measles exposures occur in a health-care facility, all contacts should be evaluated immediately for presumptive evidence of measles immunity. HCP without evidence of immunity should be offered the first dose of M M R vaccine and excluded from work from day 5-21 following exposure (135). HCP without evidence of immunity who are not vaccinated after exposure should be removed from all patient contact and excluded from the facility from day 5 after their first exposure through day 21 after the last exposure, even if they have received postexposure intramuscular immune globulin of 0.25 mL/kg (40 mg IgG/ kg) (135). Those with documentation of 1 vaccine dose may remain at work and should receive the second dose.
C ase-patient contacts who do not have presum ptive evidence of measles immunity should be vaccinated, offered intramuscular immune globulin of 0.25 mL/kg (40 mg IgG/ kg), which is the standard dosage for nonimmunocompromised persons (135), or quarantined until 21 days after their exposure to the case-patient. Contacts with measles-compatible symptoms should be isolated, and appropriate infectioncontrol measures should be implemented to prevent further spread. If immune globulin is administered to an exposed person, observations should continue for signs and symptoms of measles for 28 days after exposure because immune globulin might prolong the incubation period.
Available data suggest that live virus measles vaccine, if administered within 72 hours of measles exposure, will prevent, or modify disease (134). Even if it is too late to provide effective postexposure prophylaxis by administering MMR, the vaccine can provide protection against future exposure to all three infections. Identifying persons who lack evidence ofmeasles immunity during contact investigations provides a good opportunity to offer M M R vaccine to protect against measles as well as mumps and rubella, not only for HCP who are part of an organization' s vaccination program, but also for patients and visitors. If an exposed person is already incubating measles, M M R vaccination will not exacerbate symptoms. In these circumstances, persons should be advised that a measles-like illness occurring shortly after vaccination could be attributable either to natural infection or to the vaccine strain.
In such circumstances, specimens should be submitted for viral strain identification.

# Mumps

# Background

# Epidemiology and Risk Factors
Mumps is an acute viral infection characterized by fever and inflammation of the salivary glands (usually parotitis) (175). The spectrum of illness ranges from subclinical infection (20% -40%) to nonspecific respiratory illness, sialadenitis including classic parotitis, deafness, orchitis, and meningoencephalitis; severity increases with age (175). In the prevaccine era, mumps was a common childhood illness, with approximately 186,000 mumps cases reported in the United States per year (176). After the introduction of the Jeryl Lynn strain mumps vaccine in 1967 and the implementation of the 1-dose mumps vaccine policy for children in 1977 (177), reports of mumps cases in the United States declined 99% (178). During 1986-1987, an increase in reported mumps cases occurred, primarily affecting unvaccinated adolescents and young adults. In the late 1980s, sporadic outbreaks continued to occur that affected both unvaccinated and 1-dose vaccinated adolescents and young adults (178). In 1989, a second dose of M M R vaccine was recommended nationwide for better measles control among school-aged children (179). Historically low rates of mumps followed with only several hundred reported cases per year in the United States during 2000-2005.
In 1998, a national goal to eliminate mumps was set for 2010 (180). However, in 2006, a total of 6,584 mumps cases were reported in the United States, the largest U.S. mumps outbreak in nearly 20 years (181-183). Whereas overall national mumps incidence was 2.2 per 100,000 population, eight states in the Midwest were the most affected, with 2.5-66.1 cases per 100.000 population (183). The highest incidence (31.1 cases per 100,000 population) was among persons aged 18-24 years (e.g., college-aged students), the majority of whom had received 2 doses of mumps-containing vaccine. O f the 4,017 case-patients for whom age and vaccination status were known, 1,786 (44%) were aged >25 years (incidence: 7.2 cases per 100.000 persons); of these 1,786 patients, 351 (20%) received at least 2 doses, 444 (25%) received 1 dose, 336 (19%) were unvaccinated, and 655 (37%) had unknown vaccination status.
Since the 2006 resurgence, two additional large U.S. mumps outbreaks have occurred, both during 2009-2010, one among members o f a religious com m unity w ith cases occurring throughout the northeastern United States (184) and the other in Guam ( 185

# Mumps Transmission and the Costs of Mitigating Mumps Exposures in Health-care Settings
Although health-care-associated transmission of mumps is infrequent, it might be underreported because of the high percentage (~20%-40%) of infected persons who might be asymptomatic (186)(187)(188)(189). In a survey of 9,299 adults in different professions conducted in 1968, before vaccine was used routinely, the rate of mumps acquisition was highest among dentists and HCP, with rates of 18% among dentists and 15% among physicians (37% for pediatricians), compared with 9% among primary and secondary school teachers and 2% among university staff members (190).
In the postvaccine era, m um ps transm ission also has been documented in medical settings (191)(192)(193). During a Tennessee mumps outbreak during 1986-1987, a total of 17 (12%) of 146 hospitals and three (50%) of six long-term-care facilities reported one or more practices that could contribute to the spread of mumps, including not isolating patients with mumps, assigning susceptible staff to care for patients with mumps, and not immunizing susceptible employees. Health care-associated transmission resulted in six cases of mumps infections among health-care providers and nine cases of mumps infections among patients (191). In Utah in 1994, two health-care providers in a hospital developed mumps after they had contact with an infected patient (192). During the 2006 outbreak, one health-care facility in Chicago experienced ongoing mumps transmission lasting 4 weeks (193).
During the 2006 multistate U.S. outbreak, 144 (8.5%) of 1,705 adult case-patients in Iowa for whom occupation was known were health-care providers (Iowa D epartm ent o f Public H ealth, unpublished data, 2006). W hether transmission occurred from patients, coworkers, or persons in the community is unknown. During the 2009-2010 outbreak in the northeastern region of the United States, seven (0.2%) of the 3,400 case-patients were health-care providers, six of whom likely were infected by patients because they had no other known exposure.
Exposures to mumps in health-care settings also can result in added economic costs because of furlough or reassignment of staff members from patient-care duties or closure of wards (194). In 2006, a Kansas hospital spent $98,682 containing a mumps outbreak (195). During a mumps outbreak in Chicago in 2006, one health-care facility spent $262,788 controlling the outbreak (193).

# Vaccine Effectiveness, Duration of Immunity and Seroprevalence Studies, and Vaccine Safety
Vaccine Effectiveness M M R vaccine has a 1-dose vaccine effectiveness in preventing mumps of 80% -85% (range: 75% -91% ) (175,(196)(197)(198)(199) and a 2-dose vaccine effectiveness of 79% -95% (199)(200)(201)(202). In a study conducted on two Iowa college campuses during the 2006 mumps outbreak among a population that was primarily vaccinated with 2 doses, 2-dose vaccine effectiveness ranged from 79% to 88% (202).

# Duration of Immunity and Seroprevalence Studies
Mumps antibody levels wane over time following the first or second dose of vaccination (203,204), but the correlates of im m unity to m um ps are poorly understood and the significance of these waning antibody levels is unclear. A study on a university campus in Nebraska in 2006 indicated lower levels of mumps neutralizing antibodies among students who had been vaccinated with a second M M R dose >15 years previously than among those who had been vaccinated 1-5 years previously, but the difference was not statistically significant (p>0.05) (205). In a 2006 study on a university campus in Kansas, students with mumps were more likely to have received a second dose of M M R vaccine >10 years previously than were their roommates without mumps (206). However, another 2006 study from an Iowa college campus identified no such association (202).
During 1999-2004, national seroprevalence for mumps antibodies for persons aged 6 -4 9 years was 90% (95% confidence interval : 88.8-91.1) (207). In the Nebraska study, 414 (94%) of the 440 participants were seropositive for mumps antibodies (205). A study in Kansas in 2006 indicated that 13% of hospital employees lacked antibodies to the mumps virus (195). In a recent study on mumps seroprevalence among 381 newly hired health-care personnel at a hospital in North Carolina who were born before 1957 and thus considered immune by age and who could not provide written evidence of immunity to mumps, serologic testing indicated that 14 (3.7%) lacked IgG antibodies to mumps (157). For HCP who do not have adequate presumptive evidence of mum ps imm unity, prevaccination antibody screening before M M R vaccination is not necessary (135,175). For H C P who have 2 documented doses of M M R vaccine or other acceptable evidence of immunity to mumps, serologic testing for im m unity is not recommended. In the event that a health-care provider who has 2 docum ented doses of M M R vaccine is tested serologically and determined to have negative or equivocal mumps titer results, it is not recommended that the person receive an additional dose of M M R vaccine. Such persons should be considered immune to mumps. Documented age-appropriate vaccination supersedes the results of subsequent serologic testing. Likewise, during outbreaks of mumps, serologic screening before vaccination is not recommended because rapid vaccination is necessary to halt disease transmission.

# Controlling Mumps Outbreaks in Health-Care Settings
Placing patients in droplet precautions and implementing other infection-control measures is important to control the spread of mumps but might fail to prevent all nosocomial transmission, because transmission to other susceptible persons might occur before illness is recognized (208). W hen a person suspected of having mumps visits a health-care facility, only H C P with adequate presum ptive evidence of im m unity should be exposed to the person, and in addition to standard precautions, droplet precautions should be followed. The index case-patient should be isolated, and respiratory precautions  The first dose of mumps-containing vaccine should be administered on or after the first birthday; the second dose should be administered no earlier than 28 days after the first dose.
Mumps immunoglobulin (IgG) in the serum; equivocal results should be considered negative.   The majority of persons born before 1957 are likely to have been infected naturally between birth and 1977, the year that mumps vaccination was recommended for routine use, and may be presumed immune, even if they have not had (gown and gloves) should be used for patient contact. Negative pressure rooms are not required. The patient should be isolated for 5 days after the onset of parotitis, during which time shedding of virus is likely to occur (209).
If mumps exposures occur in a health-care facility, all contacts should be evaluated for evidence of mumps immunity. HCP with no evidence of mumps immunity who are exposed to patients with mumps should be offered the first dose of M M R vaccine as soon as possible, but vaccine can be administered at any interval following exposure; they should be excluded from duty from day 12 after the first unprotected exposure through day 25 after the most recent exposure. H C P with documentation of 1 vaccine dose may remain at work and should receive the second dose. HCP with mumps should be excluded from work for 5 days from the onset of parotitis (209).
Antibody response to the mumps com ponent of M M R vaccine generally is believed not to develop soon enough to provide effective prophylaxis after exposure to suspected mum ps (191,210), but data are insufficient to rule out a prophylactic effect. N onetheless, the vaccine is not recom m ended for prophylactic purposes after exposure. However, identifying persons who lack presumptive evidence of mumps immunity during contact investigations provides a good opportunity to offer M M R vaccine to protect against mumps as well as measles and rubella, not only for HCP who are part of an organization's vaccination program, but also for patients and visitors. If an exposed person already is incubating mumps, M M R vaccination will not exacerbate the symptoms. In these circumstances persons should be advised that a mumps-like illness occurring shortly after vaccination is likely to be attributable to natural infection. In such circumstances, specimens should be submitted for viral strain identification to differentiate between vaccine and wild type virus. Immune globulin is not routinely used for postexposure protection from mumps because no evidence exists that it is effective (135).

# Rubella

# Background

# Epidemiology and Risk Factors
Rubella (German measles) is a viral disease characterized by rash, low-grade fever, lym phadenopathy, and malaise (211). A lthough rubella is considered a benign disease, transient arthralgia and arthritis are observed commonly in infected adults, particularly among postpubertal females. Chronic arthritis has been reported after rubella infection, but such reports are rare, and evidence of an association is weak (212). O ther complications that occur infrequently are thrombocytopenia and encephalitis (211). Infection is asymptomatic in 25%-50% of cases (213). Clinical diagnosis of rubella is unreliable and should not be considered in assessing immune status. Many rash illnesses might mimic rubella infection and many rubella infections are unrecognized. The only reliable evidence of previous rubella infection is the presence of serum rubella IgG antibody (211).
O f primary concern are the effects that rubella can have when a pregnant woman becomes infected, especially during the first trimester, which can result in miscarriages, stillbirths, therapeutic abortions, and congenital rubella syndrome (CRS), a constellation of birth defects that often includes blindness, deafness, mental retardation, and congenital heart defects (211,213). Postnatal rubella is transmitted through direct or droplet contact from nasopharyngeal secretions. The incubation period ranges from 12 to 23 days (214,215). An ill person is most contagious when the rash first appears, but the period of maximal communicability extends from a few days before to 7 days after rash onset (213). Rubella is less contagious than measles.
In the prevaccine era, rubella was an endemic disease globally with larger epidemics that occurred; in the United States, rubella epidemics occurred approximately every 7 years (211). During the 1964-1965 global rubella epidemic, an estimated 12.5 million cases of rubella occurred in the United States, resulting in approximately 2,000 cases of encephalitis, 11,250 fetal deaths attributable to spontaneous or surgical abortions, 2,100 infants who were stillborn or died soon after birth, and 20,000 infants born with CRS. The economic impact of this epidemic in the United States alone was estimated at $1.5 billion in 1965 dollars ($10 billion in 2010 dollars) (216).
After the rubella vaccine was licensed in the United States in 1969, reported rubella cases decreased from 57,686 in 1969 to 12,491 in 1976 (216), and CRS cases reported nationwide decreased from 68 in 1970 to 23 in 1976 (217). Declines in rubella age-specific incidence occurred in all age groups, including adolescents and adults, but the greatest declines were among children aged <15 years (216) As of September 2011, only three states (i.e., New York, Oklahoma, and Rhode Island) had laws mandating that all hospital personnel have proof of rubella immunity and did not allow for religious or philosophical exemptions (147). Additional states had requirements for specific types of facilities or for certain employees within those facilities, but they did not have universal laws mandating proof of rubella immunity for all hospital personnel (147).

# Rubella Transmission and the Costs of Mitigating Rubella Exposures in Health-Care Settings
No documented transmission of rubella to HCP or other hospital staff or patients in U.S. health-care facilities has occurred since elimination was declared. However, in the decades before elimination, rubella transmission was documented in at least 10 U.S. medical settings (221)(222)(223)(224)(225)(226)(227)(228)(229)(230)(231) and led to outbreaks with serious consequences, including pregnancy terminations, disruption of hospital routine, absenteeism from work, expensive containment measures, negative publicity, and the threat of litigation (232). In these outbreaks, transmission occurred from HCP to susceptible coworkers and patients, as well as from patients to HCP and other patients. No data are available on whether HCP are at increased risk for acquiring rubella compared with other professions.

# Vaccine Effectiveness, Duration of Immunity and Seroprevalence Studies, and Vaccine Safety

# Vaccine Effectiveness
Vaccine effectiveness of the RA 27/3 rubella vaccine against clinical rubella is 95% (85%-99% CI) and >99% for clinical laboratory confirmed rubella (211,233). Antibody responses to rubella as part of M M R vaccine are equal (i.e., >99%) to those seen after the single-antigen RA 27/3 rubella vaccine (211,234).

# Duration of Immunity and Seroprevalence Studies
In clinical trials, 97% -99% of susceptible persons who received a single dose of the RA 27/3 rubella vaccine when they were aged >12 months developed antibody (211,235,236). Two studies have demonstrated that vaccine-induced rubella antibodies might wane after 12-15 years (237,238); however, rubella surveillance data do not indicate that rubella and CRS are increasing among vaccinated persons.
N ational seroprevalence for rubella antibodies among persons aged 6-49 years during 1999-2004 was 91% (239). During 1986-1990, serologic surveys in one hospital indicated that 5% of H C P (including persons born in 1957 or earlier) did not have detectable rubella antibody (240). Earlier studies indicated that up to 14%-19% of U.S. hospital personnel, including young women of childbearing age, lacked detectable rubella antibody (225,241,242). In a recent study on rubella seroprevalence among 477 newly hired HCP at a hospital in N orth Carolina who were born before 1957, and thus considered immune by age, who could not provide written evidence of immunity to rubella, serologic testing revealed that 14 (3.1%) lacked detectable levels of antibody to rubella (157).
Because of the potential for contact with pregnant women in any type of health-care facility, all HCP should have documented presumptive evidence of immunity to rubella. History of disease is not considered adequate evidence of immunity.  As a result of the theoretic risk to the fetus, women should be counseled to avoid becoming pregnant for 28 days after receipt of a rubella-containing vaccine (243). However, receipt of rubella-containing vaccine during pregnancy should not be a reason to consider termination of pregnancy; data from 18 years of following to term 321 known rubella-susceptible women who were vaccinated within 3 months before or 3 m onths after conception indicated that none of the 324 infants born to these mothers had malformations compatible with congenital rubella syndrome, but five had evidence of subclinical rubella infection (244). The estimated risk for serious malformations to fetuses attributable to the mother receiving RA 27/3 vaccine is considered to range from zero to 1.6% (135,244).
Evidence does not support a link between M M R vaccination and any of the following: hearing loss, retinopathy, optic neuritis, Guillain-Barre Syndrome, type 1 diabetes, Crohn's disease, or autism (135,(163)(164)(165)(166)(167)(168)(169).
A woman can excrete the rubella vaccine virus in breast milk and transmit the virus to her infant, but the infection remains asymptomatic (135) Presumptive evidence of immunity to rubella for persons who work in health-care facilities includes any of the following:
- written documentation of vaccination with 1 dose of live rubella or M M R vaccine, - laboratory evidence of im m unity,- laboratory confirmation of rubella infection or disease, or - birth before 1957* (except women of childbearing potential who could become pregnant, although pregnancy in this age group would be exceedingly ra re^).

# Prevaccination Testing
For HCP who do not have adequate presumptive evidence of rubella im m unity, prevaccination antibody screening before M M R vaccination is not necessary unless the medical facility considers it cost effective (135). For HCP who have 1 documented dose of M M R vaccine or other acceptable evidence of immunity to rubella, serologic testing for immunity is not recommended. In the event that a health-care provider who has at least 1 documented dose of rubella-containing vaccine is tested serologically and determined to have negative or equivocal rubella titer results, receipt of an additional dose of M M R vaccine for prevention of rubella is not recommended. Such persons should be considered im m une to rubella. However, if the provider requires a second dose of measles or mumps vaccine, then a second dose of M M R should be adm inistered. D ocum ented age-appropriate vaccination supersedes the results of subsequent serologic testing. Likewise, during outbreaks of rubella, serologic screening before vaccination is not recommended because rapid vaccination is necessary to halt disease transmission.

# Controlling Rubella Outbreaks
To prevent transmission of rubella in health-care settings, patients suspected to have rubella should be placed in private rooms. In addition to standard precautions, droplet precautions Because rubella can occur in some persons born before 1957 and because congenital rubella and congenital rubella syndrome can occur in the offspring of women infected with rubella virus during pregnancy, birth before 1957 is not acceptable evidence of rubella immunity for women who could become pregnant.
should be followed until 7 days after onset of symptoms. Room doors can remain open, and special ventilation is not required. Any exposed HCP who do not have adequate presumptive evidence of rubella immunity should be excluded from duty beginning 7 days after exposure to rubella and continuing through either 1) 23 days after the most recent exposure or 2) 7 days after rash appears if the provider develops rubella (213)(214)(215). Exposed H C P who do not have adequate presum ptive evidence of im m unity who are vaccinated postexposure should be excluded from duty for 23 days after the most recent exposure to rubella because no evidence exists that postexposure vaccination is effective in preventing rubella infection (244).
N either rubella-containing vaccine (244) nor im m une globulin (IG) (211,244) is effective for postexposure prophylaxis of rubella. Although intramuscular administration of 20 mL of immune globulin within 72 hours of rubella exposure might reduce the risk for rubella, it will not eliminate the risk (135,245); infants with congenital rubella have been born to women who received IG shortly after exposure (213). In addition, administration of IG after exposure to rubella might modify or suppress symptoms and create an unwarranted sense of security with respect to transmission.
If exposure to rubella does not cause infection, postexposure vaccination with M M R vaccine should induce protection against subsequent infection of rubella, as well as measles and mumps. If the exposure results in infection, no evidence indicates that administration of M M R vaccine during the presymptomatic or prodromal stage of illness increases the risk for vaccine-associated adverse events (213).

# Pertussis

# Background

# Epidemiology and Risk Factors
Pertussis is a highly contagious bacterial infection. Secondary attack rates among susceptible household contacts exceed 80% (246,247). Transmission occurs by direct contact with respiratory secretions or large aerosolized droplets from the respiratory tract of infected persons. The incubation period is generally 7-10 days but can be as long as 21 days. The period of communicability starts with the onset of the catarrhal stage and extends into the paroxysmal stage. Symptoms of early pertussis (catarrhal phase) are indistinguishable from other upper respiratory infections.
Vaccinated adolescents and adults, whose immunity from childhood vaccinations wanes 5-10 years after the most recent dose of vaccine (usually administered at age 4-6 years), are an important source of pertussis infection for susceptible infants. Infants too young to be vaccinated are at greatest risk for severe pertussis, including hospitalization and death. The disease can be transmitted from adults to close contacts, especially unvaccinated children.
Vaccination coverage am ong infants and children for diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccine remains high. In 2010, coverage for children aged 19-35 months who have received >4 doses of DTaP/diphtheria and tetanus toxoids and pertussis vaccine (DTP)/diphtheria and tetanus toxoids vaccine (DT) was 84% (21). Among children entering kindergarten for the 2009-2010 school year, DTaP coverage was 93% (148). Vaccination coverage for tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine was 68.7% among adolescents in 2010 and <7% among adults in 2009 (22,248). Tdap vaccination coverage among H C P was 17.0% in 2009 (248).

# Disease in Health-Care Settings and Impact on Health Care Personnel and Patients
In hospital settings, transmission of pertussis has occurred from hospital visitors to patients, from HCP to patients, and from patients to H C P (249-252). Although of limited size (range: 2-17 patients and 5-13 staff), documented outbreaks were costly and disruptive. In each outbreak, H C P were evaluated for cough illness and required diagnostic testing, prophylactic antibiotics, and exclusion from work.
D uring outbreaks that occur in hospitals, the risk for contracting pertussis among patients or staff is often difficult to quantify because exposure is not well defined. Serologic studies conducted among hospital staff indicate that exposure to pertussis is much more frequent than suggested by attack rates of clinical disease (246,(249)(250)(251)(252)(253)(254). In one outbreak, seroprevalence of pertussis agglutinating antibodies among H C P correlated w ith the degree of patient contact and was highest among pediatric house staff (82%) and ward nurses (71%) and lowest among nurses with administrative responsibilities (35%) (251).
A model to estimate the cost of vaccinating H CP and the net return from preventing nosocomial pertussis was constructed using probabilistic methods and a hypothetical cohort of 1,000 H C P with direct patient contact followed for 10 years (255). Baseline assumptions, determined from data in the literature, included incidence of pertussis in HCP, ratio of identified exposures per HCP case, symptomatic percentage of seroconfirmed pertussis infections in HCP, cost of infectioncontrol measures per exposed person, vaccine efficacy, vaccine coverage, employment turnover rate, adverse events, and cost of vaccine (255). In a 10-year period, the cost of infection control would be $388,000 w ithout Tdap vaccination of HCP compared with $69,000 with such a program (255). Introduction of a vaccination program would result in a net savings as high as $535,000 and a benefit-cost ratio of 2.38 (i.e., for every dollar spent on the vaccination program, the hospital would save $2.38 on control measures) (255).

# Vaccine Effectiveness, Duration of Immunity, and Vaccine Safety
A prelicensure im m unogenicity and safety study in adolescents and adults of a vaccine containing acellular pertussis estimated vaccine efficacy to be 92% (256). Recent postlicensure studies ofTdap demonstrate vaccine effectiveness at 78% and 66% (257,258). Duration of im m unity from vaccination has yet to be evaluated. D ata from pre-and postlicensure studies support the safety ofTdap in adolescents and adults (259)(260)(261)(262)(263).
Since the 2005 Tdap recommendations for HCP, one study tried to determine if postexposure prophylaxis following pertussis exposure was necessary for Tdap-vaccinated H C P (264). During the study period, 116 exposures occurred among 94 HCP. Pertussis infection occurred in 2% of those who received postexposure prophylaxis compared with 10% of those who did not, suggesting a possible benefit of postexposure prophylaxis among Tdap-vaccinated HCP (264). Because Tdap coverage is suboptimal among HCP, and the duration of protection afforded by Tdap is unknown, vaccination status does not change the approach to evaluate the need for postexposure prophylaxis in exposed H CP Postexposure prophylaxis is necessary for HCP in contact with persons at risk for severe disease. Other HCP either should receive postexposure prophylaxis or be monitored for 21 days after pertussis exposure and treated at the onset of signs and symptoms of pertussis. Recommended postexposure prophylaxis antibiotics for HCP exposed to pertussis include azithromycin, clarithroymycin, or erythromycin. HCP are not at greater risk for diphtheria or tetanus than the general population.

# Recommendations

# Vaccination
Regardless of age, H C P should receive a single dose ofTdap as soon as feasible if they have not previously received Tdap and regardless of the time since their most recent Td vaccination. Vaccinating HCP with Tdap will protect them against pertussis and is expected to reduce transmission to patients, other HCP, household members, and persons in the community. Tdap is not licensed for multiple administrations; therefore, after receipt of Tdap, H C P should receive Td for future booster vaccination against tetanus and diphtheria. Hospitals and ambulatory-care facilities should provide Tdap for H C P and use approaches that maximize vaccination rates (e.g., education about the benefits of vaccination, convenient access, and the provision of Tdap at no charge).

# Prevaccination Testing
Prevaccination serologic testing is not recommended.

# Demonstrating Immunity
Im m unity cannot be dem onstrated through serologic testing because serologic correlates of protection are not well established.

# Controlling Pertussis Outbreaks in Health-Care Settings
Prevention of pertussis transmission in health-care settings involves diagnosis and early treatment of clinical cases, droplet isolation of infectious patients who are hospitalized, exclusion from work of H C P who are infectious, and postexposure prophylaxis. Early diagnosis of pertussis, before secondary transmission occurs, is difficult because the disease is highly communicable during the catarrhal stage, when symptoms are still nonspecific. Pertussis should be considered in the differential diagnoses for any patient with an acute cough illness with severe or prolonged paroxysmal cough, particularly if characterized by posttussive vomiting, whoop, or apnea. Nasopharyngeal specimens should be taken, if possible, from the posterior nasopharynx with a calcium alginate or Dacron swab for cultures and/or polymerase chain reaction (PCR) assay.
Health-care facilities should maximize efforts to prevent transmission of Bordetella pertussis. Precautions to prevent respiratory droplet transmission or spread by close or direct contact should be employed in the care of patients admitted to hospital with suspected or confirmed pertussis (265). These precautions should remain in effect until patients are improved clinically and have completed at least 5 days of appropriate antimicrobial therapy. HCP in whom symptoms (i.e., unexplained rhinitis or acute cough) develop after known pertussis exposure might be at risk for transmitting pertussis and should be excluded from work until 5 days after the start of appropriate therapy (3).
Data on the need for postexposure prophylaxis in Tdapvaccinated H C P are inconclusive (264). Certain vaccinated H C P are still at risk for B. pertussis. Tdap might not preclude the need for postexposure prophylaxis. Postexposure antimicrobial prophylaxis is recommended for all HCP who have unprotected exposure to pertussis and are likely to expose a patient at risk for severe pertussis (e.g., hospitalized neonates and pregnant women). O ther H C P should either receive postexposure antimicrobial prophylaxis or be monitored daily for 21 days after pertussis exposure and treated at the onset of signs and symptoms of pertussis.

# Varicella

# Background

# Epidemiology and Risk Factors
Varicella is a highly infectious disease caused by primary infection with varicella-zoster virus (VZV). VZV is transmitted from person to person by direct contact, inhalation of aerosols from vesicular fluid of skin lesions of varicella or herpes zoster (HZ), a localized, generally painful vesicular rash commonly called shingles, or infected respiratory tract secretions that also might be aerosolized (266). The average incubation period is 14-16 days after exposure to rash (range: 10-21 days). Infected persons are contagious an estimated 1-2 days before rash onset until all lesions are crusted, typically 4 -7 days after rash onset (266). Varicella secondary attack rates can reach 90% among susceptible contacts. Typically, primary infection with VZV results in lifetime immunity. VZV remains dormant in sensory-nerve ganglia and can reactivate at a later time, causing H Z. Before the U.S. childhood varicella vaccination program began in 1995, approximately 90% ofvaricella disease occurred among children aged 85% in varicella incidence, hospitalizations, and deaths (267)(268)(269). The decline in disease incidence was greatest among children for whom vaccination was recommended; however, declines occurred in every age group including infants too young to be vaccinated and adults, indicating reduced communitywide transmission of VZV.
C urrent incidence of varicella am ong adults is low (<0.1/1,000 population), and adult cases represent <10% of all reported varicella cases (270). National seroprevalence data from 1999-2004 demonstrated that, in the early vaccine era, adults continued to have high immunity to varicella (271). In this study, 98% of persons aged 20-49 years had VZV-specific IgG antibodies. However, with declining likelihood of exposure to VZV, children and adolescents who did not receive 2 doses of varicella vaccine could remain susceptible to VZV infection as they age into adulthood, when varicella can be more severe.
The clinical presentation of varicella has changed since the implementation of the varicella vaccination program, with more than half of varicella cases reported in 2008 occurring among persons who were vaccinated previously, the majority of them children. Varicella disease in vaccinated children (breakthrough varicella) usually has a modified or atypical presentation; the rash is typically mild, with 50 lesions were as infectious as unvaccinated children (272). Because the majority of adults are immune and few need vaccination, fewer breakthrough cases have been reported among adults than among children, and breakthrough varicella in adults has tended to be milder than varicella in unvaccinated adults (273,274).
The epidemiology of varicella in tropical and subtropical regions differs from that in the United States. In these regions, a higher proportion ofVZV infections are acquired later in life. Persons emigrating from these regions might be more likely to be susceptible to varicella compared to U.S.-born persons and, therefore, are at a higher risk for developing varicella if unvaccinated and exposed (275,276).

# Disease in Health-Care Settings and Impact on Health Care Personnel and Patients
A lthough relatively rare in the U nited States since introduction of varicella vaccine, nosocomial transmission of VZV is well recognized and can be life-threatening to certain patients (277)(278)(279)(280)(281)(282)(283)(284)(285)(286)(287)(288)(289). In addition to hospital settings, nosocomial VZV transmission has been reported in longterm-care facilities and a hospital-associated residential facility (290,291). Sources of nosocomial exposure that have resulted in transmission include patients, HCP, and visitors with either varicella or H Z. Both localized and disseminated H Z in immunocompetent as well as immunocompromised patients have been identified as sources of nosocomial transmission of VZV. Localized H Z has been demonstrated to be much less infectious than varicella; disseminated H Z is considered to be as infectious as varicella (266). Nosocomial transmission has been attributed to delays in the diagnosis or reporting of varicella or H Z and in failures to implement control measures promptly. In hospitals and other health-care settings, airborne transmission of VZV from patients with either varicella or H Z has resulted in varicella in HCP and patients who had no direct contact with the index case-patient (284)(285)(286)(287)(288)291). Although all susceptible patients in health-care settings are at risk for severe varicella disease with complications, certain patients without evidence of immunity are at increased risk: pregnant women, premature infants born to susceptible mothers, infants born at <28 weeks' gestation or who weigh <1,000 grams regardless of maternal immune status, and immunocompromised persons of all ages (including persons who are undergoing immunosuppressive therapy, have malignant disease, or are immunodeficient).
VZV exposures among patients and HCP can be disruptive to patient care, time-consuming, and costly even when they do not result in VZV transmission (281,282,292). Studies ofVZV exposure in health-care settings have documented that a single provider with unrecognized varicella can result in the exposure of >30 patients and >30 employees (292). Identification of susceptible patients and staff, medical management of susceptible exposed patients at risk for complications of varicella, and furloughing of susceptible exposed HCP are time-consuming and costly (281,282). W ith the overall reduction in varicella disease attributable to the success of the vaccination program, the risk for exposure to VZV from varicella cases in health-care settings is likely declining. In addition, an increasing proportion of varicella cases occur in vaccinated persons who are less contagious. Diagnosis of varicella has become increasingly challenging as a growing proportion of cases occur in vaccinated persons in whom disease is mild, and HCP encounter patients with varicella less frequently. Although not currently routinely recommended for the diagnosis and management of varicella, laboratory testing of suspected varicella cases is likely to become increasingly useful in health-care settings, especially as the positive predictive value of clinical diagnosis declines.

# Vaccine Effectiveness, Duration of Immunity, and Vaccine Safety

# Vaccine Effectiveness
Formal studies to evaluate vaccine efficacy or effectiveness have not been performed among adults. Studies of varicella vaccine effectiveness performed among children indicated good performance of 1 dose for prevention of all varicella (80% -85%) and >95% effectiveness for prevention of moderate and severe disease (266,293). Studies have indicated that a second dose among children produces an improved humoral and cellular immune response that correlates with improved protection against disease (266,294).
Varicella vaccine effectiveness is expected to be lower in adults than in children. Adolescents and adults require 2 doses to achieve seroconversion rates similar to those seen in children after 1 dose (266). A study of adults who received 2 doses of varicella vaccine 4 or 8 weeks apart and were exposed subsequently to varicella in the household estimated an 80% reduction in the expected number of cases (295).

# Duration of Immunity
Serologic correlates of protection against varicella using commercially available assays have not been established for adults (266). In clinical studies, detectable antibody levels have persisted for at least 5 years in 97% of adolescents and adults who were administered 2 doses of varicella vaccine 4-8 weeks apart, but boosts in antibody levels were observed following exposures to varicella, which could account for the long-term persistence of antibodies after vaccination in these studies (295). Studies have demonstrated that whereas 25%-31% of adult vaccine recipients who seroconverted lost detectable antibodies 1-11 years after vaccination (273,296), vaccine-induced VZV-specific T-cell proliferation (marker for cell-mediated immunity ) was maintained in 94% of adults 1 and 5 years postvaccination (297). Disease was mild in vaccinated persons who developed varicella after exposure to VZV, even among vaccinees who did not seroconvert or who lost detectable antibody (273,274). Severity of illness and attack rates among vaccinated adults did not increase over time. These studies suggest that VZV-specific CMI affords protection to vaccinated adults, even in the absence of detectable antibody response.

# Vaccine Safety
The varicella vaccine has an excellent safety profile. In clinical trials, the most common adverse events among adolescents and adults were injection-site complaints (24.4% after the first dose and 32.5% after the second dose) (266,295). Varicella-like rash at the injection site occurred in 3% of vaccine recipients after the first dose and in 1% after the second. A nonlocalized rash occurred in 5.5% of vaccine recipients after the first dose and in 0.9% after the second, with a median number of lesions of five, at a peak of 7-21 and 0-23 days postvaccination, respectively (295). Data on serious adverse events among adults after varicella vaccination are limited, but the proportion of serious adverse events among all adverse events reported to the Vaccine Adverse Events Reporting System during 1995-2005 was low (5%) among both children and adults (298). Serious adverse events reported among children included pneumonia, hepatitis, H Z (some hospitalized), meningitis with H Z, ataxia, encephalitis, throm bocytopenic purpura. N ot all adverse events reported after varicella vaccination have been laboratory confirmed to be attributable to the vaccine strain VZV (266,298).
Risk for transmission of vaccine virus was assessed in placebo recipients who were siblings of vaccinated children and among healthy siblings of vaccinated leukemic children (266). The findings suggest that transmission of varicella vaccine virus from healthy persons to susceptible contacts is very rare. The risk might be increased in vaccinees in whom a varicella-like rash develops after vaccination. However, this risk is also low. The benefits of vaccinating HC P without evidence of immunity outweigh this extremely low potential risk. Since implementation of the varicella vaccine program, transmission of vaccine virus has been documented from eight persons (all of whom had a rash after vaccination) resulting in nine secondary infections among household and long-term-care facility contacts (299). No transmission has been documented from vaccinated HCP.

# Recommendations

# Vaccination
Health-care institutions should ensure that all HCP have evidence of immunity to varicella. This information should be documented and readily available at the work location. HCP without evidence of immunity to varicella should receive 2 doses of varicella vaccine administered 4-8 weeks apart. If >8 weeks elapse after the first dose, the second dose may be administered without restarting the schedule. Recently vaccinated HCP do not require any restriction in their work activities; however, HCP who develop a vaccine-related rash after vaccination should avoid contact with persons without evidence of immunity to varicella who are at risk for severe disease and complications until all lesions resolve (i.e., are crusted over) or, if they develop lesions that do not crust (macules and papules only), until no new lesions appear within a 24-hour period.
Evidence of immunity for HCP includes any of the following (266):
- written documentation of vaccination with 2 doses of varicella vaccine, - laboratory evidence o f im m unity    or laboratory confirmation of disease, - diagnosis or verification of a history of varicella disease by a health-care provider,JJJ or - diagnosis or verification of a history of H Z by a health-care provider. In health-care settings, serologic screening before vaccination of personnel without evidence of immunity is likely to be cost effective. Key factors determining cost-effectiveness include sensitivity and specificity of serologic tests, the nosocomial transmission rate, seroprevalence of VZV antibody in the personnel population, and policies for managing vaccine recipients developing postvaccination rash or who are    Commercial assays can be used to assess disease-induced immunity, but they often lack sensitivity to detect vaccine-induced immunity (i.e., they might yield false-negative results). JJJ Verification of history or diagnosis of typical disease can be provided by any health-care provider (e.g., a school or occupational clinic nurse, nurse practitioner, physician assistant, or physician). For persons reporting a history of, or reporting with, atypical or mild cases, assessment by a physician or their designee is recommended, and one of the following should be sought: 1) an epidemiologic link to a typical varicella case or to a laboratoryconfirmed case or 2) evidence of laboratory confirmation if it was performed at the time of acute disease. W hen such documentation is lacking, persons should not be considered as having a valid history of disease because other diseases might mimic mild atypical varicella.
exposed subsequently to VZV. Institutions may elect to test all unvaccinated HCP, regardless of disease history, because a small proportion of persons with a positive history of disease might be susceptible. For the purpose of screening HCP, a less sensitive and more specific commercial ELISA should be considered. The latex agglutination test can produce falsepositive results, and HCP who remained unvaccinated because of false test results subsequently contracted varicella (289).
Routine testing for varicella im m unity after 2 doses of vaccine is not recommended. Available commercial assays are not sensitive enough to detect antibody after vaccination in all instances. Sensitive tests that are not generally available have indicated that 92% -99% of adults develop antibodies after the second dose (266). Seroconversion does not always result in full protection against disease and, given the role of CMI for providing long-term protection, absence of antibodies does not necessarily mean susceptibility. Documented receipt of 2 doses of varicella vaccine supersedes results of subsequent serologic testing.
Health-care institutions should establish protocols and recommendations for screening and vaccinating HCP and for management of H CP after exposures in the work place. Institutions also should consider precautions for H C P in whom rash occurs after vaccination, although they should also consider the possibility of wild-type disease in HCP with recent exposure to varicella or HZ.
A vaccine to prevent H Z is available and recommended for all persons aged >60 years without contraindications to vaccination. H Z vaccine is not indicated for HCP for the prevention of nosocomial transmission, but HCP aged >60 years may receive the vaccine on the basis of the general recom m endation for H Z vaccination, to reduce their individual risk for HZ.

# Varicella Control Strategies
Appropriate measures should be implemented to manage cases and control outbreaks (300).

# Patient Care
Only HCP with evidence of immunity to varicella should care for patients who have confirmed or suspected varicella or HZ. Airborne precautions (i.e., negative air-flow rooms) and contact precautions should be employed for all patients with varicella or disseminated H Z and for immunocompromised patients with localized H Z until disseminated infection is ruled out. These precautions should be kept in place until lesions are dry and crusted. If negative air-flow rooms are not available, patients should be isolated in closed rooms and should not have contact with persons without evidence of immunity to varicella. For immunocompetent persons with localized HZ, standard precautions and complete covering of the lesions are recommended.

# Postexposure Management of HCP and Patients
Exposure to V ZV is defined as close contact w ith an infectious person, such as close indoor contact (e.g., in the same room) or face-to-face contact. Experts differ regarding the duration of contact; some suggest 5 minutes, and others up to 1 hour; all agree that it does not include transitory contact (301).
All exposed, susceptible patients and H C P should be identified using the criteria for evidence of immunity. An additional criterion of evidence of immunity only for patients who are not immunocompromised or pregnant is birth in the United States before 1980. Postexposure prophylaxis with vaccination or varicella-zoster immunoglobulin, depending on immune status, of exposed HCP and patients without evidence of immunity is recommended (266).
HCP who have received 2 doses of vaccine and who are exposed to VZV (varicella, disseminated H Z, and uncovered lesions of a localized HZ) should be monitored daily during days 8-21 after exposure for fever, skin lesions, and systemic symptoms suggestive of varicella. H C P can be monitored directly by occupational health program or infection-control practitioners or instructed to report fever, headache, or other constitutional symptoms and any atypical skin lesions immediately. HCP should be excluded from a work facility immediately if symptoms occur. H C P who have received 1 dose of vaccine and who are exposed to VZV (varicella, disseminated H Z, and uncovered lesions of a localized HZ) (in the community or health-care setting/workplace) should receive the second dose within 3-5 days after exposure to rash (provided 4 weeks have elapsed after the first dose). After vaccination, management is similar to that of 2-dose vaccine recipients. Those who did not receive a second dose or who received the second dose >5 days after exposure should be excluded from work for 8-21 days after exposure.
Unvaccinated HCP who have no other evidence of immunity who are exposed to VZV (varicella, disseminated H Z, and uncovered lesions of a localized HZ) are potentially infective from days 8-21 after exposure and should be furloughed during this period. They should receive postexposure vaccination as soon as possible. Vaccination within 3-5 days of exposure to rash might modify the disease if infection occurred. Vaccination >5 days postexposure is still indicated because it induces protection against subsequent exposures (if the current exposure did not cause infection). For HCP at risk for severe disease for whom varicella vaccination is contraindicated (e.g., pregnant or immunocomprosed HCP), varicella-zoster immune globulin after exposure is recommended. The varicella-zoster immune globulin product currently used in the United States, VariZIG (Cangene Corporation, Winnipeg, Canada), is available under an Investigational New Drug Application Expanded Access protocol; a sample release form is available at . gov/downloads/BiologicsBloodVaccines/SafetyAvailability/ UCM 176031.pdf. Varicella-zoster immune globulin might prolong the incubation period by a week, thus extending the time during which personnel should not work from 21 to 28 days. In case of an outbreak, H C P without evidence of immunity who have contraindications to vaccination should be excluded from the outbreak setting through 21 days after rash onset of the last identified case-patient because of the risk for severe disease in these groups. If the VZV exposure was to localized H Z with covered lesions, no work restrictions are needed if the exposed HCP had previously received at least 1 dose of vaccine or received the first dose within 3-5 days postexposure. A second dose should be administered at the appropriate interval. H C P should be monitored daily during days 8-21 after exposure for fever, skin lesions, and systemic symptoms suggestive of varicella and excluded from a work facility if symptoms occur. If at least 1 dose was not received, restriction from patient contact is recommended.

# Diseases for W hich Vaccination Might
Be Indicated in Certain Circum stances Health-care facilities and other organizations should consider including in their vaccination programs vaccines to prevent meningococcal disease, typhoid fever, and polio for H CP who have certain health conditions or who work in laboratories or regions outside the United States where the risk for workrelated exposure exists.

# Meningococcal Disease

# Background

# Epidemiology and Risk Factors
Meningococcal disease is rare among adults in the United States and incidence has decreased to historic lows; during 1998-2007 the average annual incidence of meningococcal disease was 0.28 (range: 0.26-0.31) cases per 100,000 population among persons aged 25-64 years (302).
Routine vaccination with meningococcal conjugate vaccine is recommended by ACIP for adolescents aged 11-18 years, with the primary dose at age 11-12 years and the booster dose at age 16 years. In 2010, coverage with meningococcal conjugate vaccine among persons aged 13-17 years was 62.7% (22). Nosocomial transmission of Neisseria meningitidis is rare, but H C P have become infected after direct contact with respiratory secretions of infected persons (e.g., managing of an airway during resuscitation) and in a laboratory setting. HCP can decrease the risk for infection by adhering to precautions to prevent exposure to respiratory droplets (303,304) and by taking antimicrobial chemoprophylaxis if exposed directly to respiratory secretions.

# Vaccine Effectiveness, Duration of Immunity, and Vaccine Safety
Two quadrivalent (A, C, W-135, Y) conjugate meningococcal vaccines (MCV4) are licensed for persons aged through 55 years (305,306). Both protect against two of the three serogroups that cause the majority of meningococcal disease in the United States and against 75% of disease among adults. Available data indicate that the majority of persons do not have enough circulating functional antibody to be protected >5 years after a single dose of MCV4. Both vaccines had similar safety profiles in clinical trials. Quadrivalent (A, C, W -135, Y) meningococcal polysaccharide vaccine (MPSV4) is available for use in persons aged >55 years. No vaccine for serogroup B meningococcal disease is licensed in the United States.

# Recommendations

# Vaccination

# M CV4 is not recommended routinely for all HCP

# HCP Recommended to Receive Vaccine to Prevent Meningococcal Disease
A 2-dose vaccine series is recommended for H C P with know n asplenia or persistent com plem ent com ponent deficiencies, because these conditions increase the risk for meningococcal disease. HCP traveling to countries in which meningococcal disease is hyperendemic or epidemic also are at increased risk for infection and should receive vaccine. Those with known asplenia or persistent complement component deficiencies should receive a 2-dose vaccine series. All other HCP traveling to work to high-risk areas should receive a single dose of M CV4 before travel if they have never received it or if they received it >5 years previously. Clinical microbiologists and research microbiologists who might be exposed routinely to isolates of N. meningitides should receive a single dose of M CV4 and receive a booster dose every 5 years if they remain at increased risk. Health-care personnel aged >55 years who have any of the above risk factors for meningococcal disease should be vaccinated with MPSV4 (305).

# HCP Who May Elect to Receive Vaccine to Prevent Meningococcal Disease
H CP with known HIV infection are likely at increased risk for meningococcal disease and may elect vaccination. If these HCP are vaccinated, they should receive a 2-dose vaccine series (307).

# Booster Doses
H CP who receive the 2-dose M CV4 vaccine series and/or remain in a group at increased risk should receive a booster dose every 5 years (306).

# Postexposure Management of Exposed HCP
Postexposure prophylaxis is advised for all persons who have had intensive, unprotected contact (i.e., without wearing a mask) with infected patients (e.g., via m outh-to-m outh resuscitation, endotracheal intubation, or endotracheal tube management), including HCP who have been vaccinated with either the conjugate or polysaccharide vaccine (3).
A ntim icrobial prophylaxis can eradicate carriage o f N. meningitidis and prevent infections in persons who have unprotected exposure to patients w ith m eningococcal infections (305). Rifampin, ciprofloxacin, and ceftriaxone are effective in eradicating nasopharyngeal carriage of N. meningitidis. In areas of the United States where ciprofloxacinresistant strains of N. meningitidis have been detected (as of August 30, 2011, only parts of Minnesota and North Dakota), ciprofloxacin should not be used for chemoprophylaxis (308). Azithromycin can be used as an alternative. Ceftriaxone can be used during pregnancy. Postexposure prophylaxis should be administered within 24 hours of exposure when feasible; postexposure prophylaxis administered >14 days after exposure is of limited or no value (305). H C P not otherwise indicated for vaccination may be recommended to be vaccinated with meningococcal vaccine in the setting of a com m unity or institutional outbreak of meningococcal disease caused by a serogroup contained in the vaccine.

# Typhoid Fever

# Background

# Epidemiology and Risk Factors
The incidence of typhoid fever declined steadily in the United States during 1900-1960 and has since remained low. During 1999-2006, on average, 237 cases were reported annually to the National Typhoid and Paratyphoid Fever Surveillance System (309). The median age of patients was 22 years and 54% were male; 79% reported foreign travel during the 30 days before onset of symptoms. Among international travelers, the risk for Salmonella Typhi infection appears to be highest for those who visit friends and relatives in countries in which typhoid fever is endemic and for those who visit (even for a short time) the most highly endemic areas (e.g., the Indian subcontinent) (310).
Increasing resistance to flu o ro q u in o lo n es such as ciprofloxacin, which are used to treat multidrug-resistant. S. Typhi, has been seen particularly among travelers to south and southeast Asia (311). Isolates with decreased susceptibility to ciprofloxacin (DCS) do not qualify as resistant according to current Clinical and Laboratory Standards Institute criteria but are associated with poorer clinical outcomes (311,312). Resistance to nalidixic acid, a quinolone, is a marker for DCS and increased from 19% in 1999 to 59% in 2008 (313). Nine isolates resistant to ciprofloxacin also were seen during this time period (313).
Although overall S. Typhi infections have declined in the United States, increased incidence and antimicrobial resistance including resistance to fluoroquinolones have been seen for paratyphoid fever caused by Paratyphi A (314). No vaccines that protect against Paratyphi A infection are available.

# Transmission and Exposure in Health-Care Settings
During 1985-1994, seven cases oflaboratory-acquired typhoid fever were reported among persons working in microbiology laboratories, only one of whom had been vaccinated (315). Additionally, S. Typhi might be transmitted nosocomially via the hands of infected persons (315).

# Vaccine Effectiveness, Duration of Immunity, and Vaccine Safety
Two typhoid vaccines are distributed in the United States: oral live-attenuated Ty21a vaccine (one enteric-coated capsule taken on alternate days for a total of four capsules) and the capsular polysaccharide parenteral vaccine (1 0.5 mL intramuscular dose). Both vaccines protect 50% -80% of recipients. To maintain immunity, booster doses of the oral vaccine are required every 5 years, and booster doses of the injected vaccine are required every 2 years. Complication rates are low for both types of S. Typhi vaccines. During 1994-1999, serious adverse events requiring hospitalization occurred in an estimated 0.47 to 1.3 per 100,000 doses, and no deaths occurred (310). However, live-attenuated Ty21a vaccine should not be used among immunocompromised persons, including those infected with HIV (316). Theoretic concerns have been raised about the immunogenicity of live, attenuated Ty21a vaccine in persons concurrently receiving antimicrobials (including antimalarial chemoprophylaxis), viral vaccines, or immune globulin (317). A third type of vaccine, a parenteral heat-inactivated vaccine associated with higher reactogenicity, was discontinued in 2000 (310,318).

# Vaccination
M icrobiologists and others who work frequently with S. Typhi should be vaccinated with either of the two licensed and available vaccines. Booster vaccinations should be administered on schedule according to the manufacturers' recommendations.

# Controlling the Spread of Typhoid Fever
Personal hygiene, particularly hand hygiene before and after all patient contacts, will minimize risk for transmitting enteric pathogens to patients. However, H C P who contract an acute diarrheal illness accompanied by fever, cramps, or bloody stools are likely to excrete substantial numbers of infective organisms in their feces. Excluding these H C P from care of patients until the illness has been evaluated and treated can prevent transmission (3).

# Poliomyelitis

# Background

# Epidemiology and Risk Factors
In the United States, the last indigenously acquired cases of poliomyelitis caused by wild poliovirus occurred in 1979, and the Americas were certified to be free of indigenous wild poliovirus in 1994 (319,320). W ith the complete transition from use of oral poliovirus vaccine (OPV) to inactivated poliovirus vaccine (IPV) in 2000, vaccine-associated paralytic poliomyelitis (VAPP) attributable to O PV also has been eliminated (321,322)

# Transmission and Exposure in Health-Care Settings
Poliovirus can be recovered from infected persons, including from pharyngeal specim ens, feces, urine, and (rarely) cerebrospinal fluid. H C P and laboratory workers might be exposed if they come into close contact with infected persons (e.g., travelers returning from areas where polio is endemic) or with specimens that contain poliovirus.

# Recommendations Vaccine Effectiveness, Duration of Immunity, and Vaccine Safety
Both IPV and OPV are highly immunogenic and effective when administered according to their schedules. In studies conducted in the United States, 3 doses of IPV resulted in 100% serocoversion for types 2 and 3 poliovirus and 96%-100% for type 1 (326). Imm unity is prolonged and might be lifelong. IPV is well tolerated, and no serious adverse events have been associated with its use. IPV is an inactivated vaccine and does not cause VAPP IPV is contraindicated in persons with a history of hypersensitivity to any component of the vaccine, including 2-phenoxyethanol, formaldehyde, neomycin, streptomycin, and polymyxin B. OPV is no longer available in the United States.

# Recommendations

# Vaccination
Because the majority of adults born in the United States are likely immune to polio as a result of vaccination during childhood, poliovirus vaccine is not routinely recommended for persons aged >18 years. The childhood recommendation for poliovirus vaccine consists of 4 doses at ages 2, 4, and 6-18 months and 4-6 years.
However, vaccination is recommended for H C P who are at greater risk for exposure to polioviruses than the general population, including laboratory workers who handle specimens that might contain polioviruses and H C P who have close contact with patients who might be excreting wild polioviruses, including H CP who travel to work in areas where polioviruses are circulating.
Unvaccinated H C P should receive a 3-dose series of IPV, with dose 2 administered 4-8 weeks after dose 1, and dose 3 administered 6-12 months after dose 2. H C P who have previously completed a routine series of poliovirus vaccine and who are at increased risk can receive a lifetime booster dose of IPV if they remain at increased risk for exposure. Available data do not indicate the need for more than a single lifetime booster dose with IPV for adults.

# Controlling the Spread of Poliovirus
Standard precautions always should be practiced when handling biologic specim ens. Suspect cases require an immediate investigation including collection of appropriate laboratory specimens and control measures. All suspect or confirmed cases should be reported immediately to the local or state health department.

# Other Vaccines Recom m ended
for Adults Certain vaccines are recommended for adults based on age or other individual risk factors but not because of occupational exposure (327). Vaccine-specific ACIP recommendations should be consulted for details on schedules, indications, contraindications, and precautions for these vaccines.
- to be at increased risk for hepatitis A virus infection because of occupational exposure, including persons exposed to sewage. Hepatitis A vaccine is recommended for person w ith chronic liver disease, international travelers, and certain other groups at increased risk for exposure to hepatitis A.

# Catch-Up and Travel Vaccination

# Catch-Up Programs
Managers of health-care facilities should implement catch-up vaccination programs for HCP who already are employed, in addition to developing policies for achieving high vaccination coverage among newly hired HCP HCP vaccination records could be reviewed annually during the influenza vaccination season or concurrent with annual TB testing. This strategy could help prevent outbreaks of vaccine-preventable diseases. Because education, especially when combined with other interventions such as reminder/recall systems and low or no out-of-pocket costs, enhances the success of many vaccination programs, informational materials should be available to assist in answering questions from HCP regarding the diseases, vaccines, and toxoids as well as the program or policy being implemented (120,328). Conducting educational workshops or seminars several weeks before the initiation of a catch-up vaccination program might promote acceptance of program goals.

# Travel
Hospital personnel and other H C P who perform research or health-care work in foreign countries might be at increased risk for acquiring certain diseases that can be prevented by vaccines recommended in the United States (e.g., hepatitis B, influenza, M M R , T dap , poliovirus, varicella, and meningococcal vaccines) and travel-related vaccines (e.g., hepatitis A, Japanese encephalitis, rabies, typhoid, or yellow fever vaccines) (329). Elevated risks for acquiring these diseases might stem from exposure to patients in health-care settings (e.g., poliomyelitis and meningococcal disease) but also might arise from circumstances unrelated to patient care (e.g., high endemicity of hepatitis A or exposure to arthropod-vector diseases ). All H C P should seek the advice of a health-care provider familiar with travel medicine at least 4-6 weeks before travel to ensure that they are up to date on routine vaccinations and that they receive vaccinations recommended for their destination (329). Although bacille Calmette-Guerin vaccination is not recommended routinely in the United States, H C P should discuss potential beneficial and other consequences of this vaccination with their health care provider.

# Work Restrictions
W ork restrictions for susceptible H C P (i.e., no history of vaccination or documented lack of immunity) exposed to or infected with certain vaccine-preventable diseases can range from restricting individual HCP from patient contact to complete exclusion from duty (Table 5). A furloughed employee should be considered in the same category as an employee excluded from the facility. Specific recommendations concerning work restrictions in these circumstances have been published previously (3,11).   The risk for rubella vaccine-associated malformations in the offspring o f women pregnant when vaccinated or who become pregnant w ithin 1 month after vaccination is negligible.11 Such women should be counseled regarding the theoretical basis o f concern for the fetus.

# vaccine.
See table footnotes on page 41   111 Commercial assays can be used to assess disease-induced immunity, but they often lack sensitivity to detect vaccine-induced im m unity (i.e., they m ight yield false-negative results).    Verification o f history or diagnosis o f typical disease can be provided by any health-care provider (e.g., school or occupational clinic nurse, nurse practitioner, physician assistant, or physician). For persons reporting a history of, or reporting with, atypical or mild cases, assessment by a physician or their designee is recommended, and one o f the following should be sought: 1) an epidemiologic link to a typical varicella case or to a laboratory-confirm ed case or 2) evidence o f laboratory confirmation if it was performed at the tim e o f acute disease. When such documentation is lacking, persons should not be considered as having a valid history o f disease because other diseases m ight mimic mild atypical varicella. 111 For example, immunocompromised patients or pregnant women.    Those who develop acute respiratory symptoms w ith o u t fever should be considered for evaluation by occupational health to determine appropriateness o f contact with patients and can be allowed to work unless caring for patients in a protective environment; these personnel should be considered for temporary reassignment or exclusion from work for 7 days from symptom onset or until the resolution o f all noncough symptoms, whichever is longer. If symptoms such as cough and sneezing are still present, HCP should wear a facemask during patient care activities. The im portance of performing frequent hand hygiene (especially before and after each patient contact) should be reinforced.
Measles