Lead In Tap Water: CDC Public Health Communications Need Improvement
Released: 2011-04-04T00:00:00

Letter

Background

The MMWR series is one of three scientific publications published by CDC and is regarded as CDC’s flagship publication. The publication’s primary audience is made up of professionals, including medical professionals, such as clinicians, and state and local public health officials, and the publication also reaches CDC’s federal partners, such as EPA and the Centers for Medicare & Medicaid Services (CMS). In addition to the weekly reports, the MMWR series also includes MMWR Recommendations and Reports, which contain in-depth articles that relay policy statements for prevention and treatment on all areas in CDC’s scope of responsibility, such as recommendations from CDC advisory committees. CDC can also issue articles that it calls Dispatches to allow for immediate publication of urgent public health information. The Dispatches are generally subsequently published in the MMWR. The April 2, 2004, MMWR weekly report included an article on the BLLs of District residents that was first published as a Dispatch on March 30, 2004.

Exposure to Lead in the Environment

Lead is a dangerous contaminant commonly found in the environment that can affect almost every organ and system in the body. The main target for lead toxicity is the nervous system. In addition to causing behavior problems and learning disabilities in young children, elevated BLLs can cause such effects as damage to the brain and kidneys. In pregnant women, elevated BLLs may cause miscarriage.

Drinking contaminated tap water is one way humans may be exposed to lead. While measures taken during the past two decades have greatly reduced exposures to lead in tap water, lead still can be found in some metal water fixtures, interior water pipes, or pipes connecting a house to the main water pipe in the street. Lead in tap water usually comes from the corrosion of older fixtures; lead service lines, including lead service pipes; or the solder that connects pipes.

Federal law requires that blood lead screening tests be made available to all children enrolled in Medicaid. CMS’s State Medicaid Manual requires that these screenings be performed at ages 12 and 24 months and that all children aged 36 to 72 months who have not previously been screened also receive a blood lead test. The American Academy of Pediatrics agrees with these requirements for screening and has also stated that efforts must continue to test children who are at high risk for lead exposure. Beginning in 1995, elevated BLLs—the first noninfectious condition—were designated as a nationally notifiable condition reportable to CDC. The District (along with 36 states and the city of New York) has reported elevated BLLs of 10 micrograms per deciliter (μg/dL) of blood or higher for children to CDC. The District has reported this BLL information to CDC since 1997.

The District’s Childhood Lead Poisoning Screening and Reporting Act of 2002 requires that each health care provider or facility in the District perform a blood test for lead poisoning as part of a well-child care visit for each child that they serve who is under the age of six and resides in the District. The test must occur between ages 6 months and 14 months, and a second test must occur between ages 22 months and 26 months. Both tests must be performed unless parental consent is withheld or an identical test has already been performed within the previous 12 months. If a child’s age exceeds 26 months and a blood lead screening has not been performed, the child must be screened twice before age 6. The District also requires health care providers or facilities to report the results of blood tests for lead poisoning on every child under age 6 who resides in the District to the child’s parents.

CDC’s Roles and Responsibilities regarding Lead

As the nation’s public health agency, CDC has set levels of concern—the BLL that should prompt public health actions—for lead exposure since the 1960s. In 1991, CDC set the level of concern at 10 μg/dL of blood for children aged 6 months to 15 years and 25 μg/dL for adults. However, CDC has also recognized that a BLL of 10 μg/dL does not define a threshold for the harmful effects of lead—in other words, no safe blood lead level has been identified for children.

The Lead Contamination Control Act of 1988 authorized CDC to initiate programs to eliminate childhood lead poisoning in the United States. As a result of this act, the CDC Childhood Lead Poisoning Prevention Program (CLPPP) was created. One of the program’s primary responsibilities is to educate the public and health care providers about childhood lead poisoning. CDC’s CLPPP also provides funding to state and local health departments to determine the extent of childhood lead poisoning by screening children for elevated BLLs. Since the inception of CDC’s lead program, nearly 60 state and local jurisdictions have received funding for their state and local CLPPPs. CDC’s efforts contribute to the Healthy People 2020 initiative, which includes an objective to eliminate elevated BLLs in children. As of 2007 to 2008, the latest years for which data were available, approximately 1.2 percent of children aged 1 to 5 years nationwide had BLLs exceeding 10 µg/dL.

In addition, the Advisory Committee on Childhood Lead Poisoning Prevention advises and guides CDC regarding new scientific knowledge and technical developments and their practical implications for childhood lead poisoning prevention efforts. In November 2010, the advisory committee initiated a work group to recommend new approaches, terminology, and strategies for defining elevated BLLs among children.

EPA’s Roles and Responsibilities regarding Lead

Under the Safe Drinking Water Act, EPA is responsible for regulating contaminants that may pose a public health risk and that are likely to be present in public water supplies, including lead. EPA’s Lead and Copper Rule established a 15 parts per billion (ppb) lead action level as a regulatory standard for water utilities in an effort to prevent and mitigate the adverse health consequences resulting from elevated lead levels in drinking water. Water systems must sample tap water at locations that are at high risk of lead contamination, generally because they are served by lead service lines or are likely to contain lead solder in the household plumbing. If more than 10 percent of the samples at residences contain lead levels over 15 ppb, the water systems must take action to lower these levels, such as replacing lead service lines in the distribution system or treating water to reduce its corrosion of the service lines, and notify EPA and residents.

The District’s Elevated Water Lead Levels Prior to CDC’s Involvement

The District’s Water and Sewer Authority owns and operates a system that delivers water—produced by the U.S. Army Corps of Engineers Washington Aqueduct—to customers in the District. In 2000, the Washington Aqueduct began to use chloramine instead of chlorine in its disinfection process. This change likely contributed to elevated water lead levels.

By late 2001, the Water and Sewer Authority became aware that the levels of lead in the District’s tap water were above EPA’s limit of 15 ppb, and it notified EPA of that fact in August 2002. Beginning in 2002, the Water and Sewer Authority notified its customers of the elevated water lead levels by issuing notices, distributing educational brochures, and holding public meetings. In the fall of 2003, the Water and Sewer Authority requested assistance from DCDOH in responding to District residents’ inquiries about the health effects of the elevated water lead levels. District residents, including infants and children, would have been exposed to elevated levels of lead in tap water during this period if they used unfiltered water for drinking, cooking, or preparing infant formula or juice.

Information in the 2004 MMWR Article

Staff from NCEH, along with individuals from DCDOH and the U.S. Public Health Service, contributed to CDC’s investigation on the effect of lead in the District’s tap water on the BLLs of residents, which was presented in the April 2, 2004, MMWR article. The 2004 MMWR article reported the results of two analyses from CDC’s investigation, which was conducted in February and March 2004. (See app. I for a copy of the 2004 MMWR article.) The first analysis was conducted to identify trends in BLLs in District residents before and after the changes in the water disinfection process. The second analysis was conducted to determine whether residents in homes with the highest water lead levels (300 ppb or greater) had BLLs at or above CDC’s level of concern of 10 μg/dL.

The summary statement of the 2004 MMWR article’s findings noted that the elevated water lead levels might have contributed to a small increase in BLLs among District residents. The article’s Editorial Note section opened with a sentence that incorrectly stated the results of the first analysis. The sentence read, “The findings in this report indicate that although lead in tap water contributed to a small increase in BLLs in D.C., no children were identified with BLLs ≥ 10 μg/dL, even in homes with the highest water lead levels.” The statement that “no children were identified with BLLs ≥ 10 μg/dL” was incorrect, relative to the first analysis. Since the 2004 MMWR article was published, CDC officials have said that in its first analysis some children were identified with BLLs ≥ 10 μg/dL, which is CDC’s level of concern for children. The last part of the statement indicating that none of the children in homes with the highest water lead levels had BLLs > 10 μg/dL was correct, in that none of the 30 children in the second analysis had BLLs that reached CDC’s level of concern, according to CDC officials. While the 2004 MMWR article discussed some limitations to its findings, it did not discuss other limitations that addressed how information in the 2004 MMWR article could be used. For example, it did not state that the article should not be used to make conclusions about the contribution of lead in tap water to BLLs in the District.

Confusion about the 2004 MMWR Article’s Findings

The statement in the 2004 MMWR article that incorrectly links the results of the two analyses in the same editorial note and the incomplete description of the limitations to the article’s findings have resulted in this information being interpreted in the press and by others in ways other than as CDC intended. For example: In a May 2004 hearing before the House Committee on Government Reform, some business and environmental advocates included references to the 2004 MMWR article to (1) support their assertion that the elevated water lead levels did not warrant a panicked reaction in the District or (2) draw conclusions about the relationship between BLLs and water lead levels in the District, which CDC later stated were inappropriate.

In July 2004, a newspaper article from a major metropolitan city that was experiencing elevated lead levels in schools’ tap water included information about the 2004 MMWR article’s findings to support statements that downplayed the seriousness of the effect of elevated water lead levels in the city on the health of children.

In a February 2008 fact sheet, the Water and Sewer Authority referenced the 2004 MMWR article and included statements that gave the impression that the health of District children had not been affected by elevated lead levels in the District’s tap water.

In February 2009, the General Manager of the Water and Sewer Authority was quoted in a newspaper article as saying that CDC’s view was that residents’ health had not been affected by elevated water lead levels in the District.

As recently as December 2010, news articles in the District reported that in the 2004 MMWR article CDC indicated that it found no evidence of measurable or significant harm to the public health of District children from elevated lead levels in tap water.

In addition, CDC officials have recognized that the 2004 MMWR article may have led people to conclude that there was no danger to children from the elevated water lead levels.

CDC Has Issued Statements to Address Confusion It Created Related to the 2004 MMWR Article, but Has Not Published an Overview of the Effects of Lead in Tap Water on BLLs in Children

Although CDC does not have a policy to monitor the use of or clarify information in public health publications, such as the information in the 2004 MMWR article, the agency issued statements to address confusion it created related to elevated lead levels in the District’s tap water. However, as of January 2011, the agency had no plans to publish an overview of the current knowledge about the effects of lead in tap water on BLLs in children. Specifically, CDC has not published an overview of what is known and not known about tap water as a source of lead exposure and the potential health effects on children, as suggested by the CDC internal incident analysis.

CDC Has Issued Statements and Taken Other Actions to Address Confusion It Created Related to the 2004 MMWR Article

CDC officials told us that although the agency does not have a policy to monitor the use or clarify interpretations of information in public health publications, such as the 2004 MMWR article, the agency has issued statements to address confusion it created related to the 2004 MMWR article. Specifically, agency officials said they have taken some actions since 2006 to address confusion CDC created about the 2004 MMWR article when they became aware of specific instances of confusion. For example: In July 2006, a CDC official was interviewed for an article published in an environmental science journal and provided information to address public statements attributed to a health advisor for the District’s Water and Sewer Authority that incorrectly characterized information from the 2004 MMWR article. The CDC official stated that the 2004 MMWR article did not say that drinking water with very high water lead levels, such as those found in some District homes, was safe.

In February 2008, a CDC official corresponded with the District’s Water and Sewer Authority officials about a statement in a February 2008 fact sheet published by the water authority that incorrectly characterized information in the 2004 MMWR article. Specifically, the CDC official noted that the fact sheet misstated the conclusions of the 2004 MMWR article and gave the impression that the health of District residents had not been affected by elevated lead levels in the tap water. The CDC official requested that the statement be corrected. In April 2009, the Director of NCEH sent a letter to the General Manager of the water authority noting that this correction and others had not been made and once again asked that statements published in the fact sheet be corrected to accurately reflect the conclusions in the 2004 MMWR article: that because no threshold for adverse health effects in young children had been demonstrated, public health interventions should focus on eliminating all lead exposures in children.

In 2009, the Chief of the Healthy Homes and Lead Poisoning Prevention Branch contacted officials responsible for drinking water safety in Seattle and New York City to discuss reports that officials were quoted in newspaper articles in those localities and had mischaracterized information in the 2004 MMWR article to downplay the effect of lead in water and that these cities had relaxed their drinking water standards based on the 2004 MMWR article. The CDC official said that she contacted the officials to clarify the 2004 MMWR article’s message about the public health effect of elevated lead levels in the District’s tap water and was assured that they had not used the 2004 MMWR article to make any changes in their drinking water standards.

More recently, CDC sent a letter to state and local CLPPP managers, published articles in the MMWR, and contacted District newspaper officials to address confusion it created related to the 2004 MMWR article. Specifically: In May 2010, CDC provided clarifying information in a letter to state and local CLPPP managers. (See app. II for a copy of the May 2010 letter.) The Chief of the Healthy Homes and Lead Poisoning Prevention Branch sent a letter dated May 20, 2010, to state and local CLPPP managers saying that the first sentence in the Editorial Note section in the 2004 MMWR article incorrectly stated the results of the first analysis, as some children were identified with BLLs above 10 μg/dL. Additionally, the letter presented results of a 2009 analysis that included new BLL data that had not been available to CDC in 2004. The letter further stated that the results of this new analysis confirmed the original finding, which CDC stated was that lead in water was associated with an increase in BLLs. The letter also restated CDC’s intended message presented in the 2004 MMWR article— that no safe blood lead level had been identified and all sources of lead exposure should be controlled or eliminated. The letter was also posted on the CDC Web site.

On May 21, 2010, CDC issued a Notice to Readers in the MMWR providing the same information about the 2009 analysis and addressing the confusion CDC created related to the 2004 MMWR article. (See app. III for a copy of the May 21, 2010, MMWR Notice to Readers.)

On June 25, 2010, CDC issued a Notice to Readers in the MMWR noting the limitations of the results of the second analysis in the 2004 MMWR article. (See app. IV for a copy of the June 25, 2010, MMWR Notice to Readers.) The Notice to Readers stated that the results of the second analysis should not be used to (1) make conclusions about the contribution of lead in tap water to BLLs in the District, (2) predict what might occur in other situations where lead levels in tap water are high, or (3) determine safe levels of lead in tap water.

In December 2010, CDC officials said that they contacted a District newspaper when it published news reports that included misinterpretions of the results of the 2004 MMWR article. CDC officials said that they contacted the newspaper the same day that the first news report was published, and for several days thereafter when additional news reports were published, to request clarifications. CDC officials told us that they also had submitted a letter to the newspaper to provide more information to help ensure that the public correctly understood the 2004 MMWR article’s intended message. The letter was published in December 2010 and stated that CDC’s opinion on the health impact of lead in the District’s water supply has not changed and that a new study reports what the agency has been saying since 2004—the presence of lead service lines increases the BLLs in the District’s children.

CDC Has Not Published an Overview of the Effects of Lead in Tap Water on BLLs in Children

Although CDC has taken actions to address confusion specific to the 2004 MMWR article, as of January 2011, CDC had not taken action to publish an overview of the current knowledge about the contribution of elevated lead levels in tap water to BLLs in children and the associated health effects. The 2010 internal incident analysis of CDC’s involvement in and response to issues surrounding elevated water lead levels in the District noted that because the relative contribution of tap water to elevated BLLs in children has become more apparent as exposure to lead paint and leaded gasoline has been reduced or eliminated, a systematic evaluation of the relative contribution of tap water to elevated BLLs should be conducted. Specifically, the internal incident analysis suggested that CDC conduct such an evaluation and publish the information in an article in the MMWR Recommendations and Reports that would serve as a position paper covering the issues of lead in municipal water supplies and summarizing what is known and not known about its contribution to historic and contemporary BLLs in children. A CDC official said that as of January 2011, CDC had no plans to conduct such an evaluation and publish an overview on the effects of lead in water on BLLs in children in the MMWR Recommendations and Reports. CDC noted that while the agency does not lack the authority to undertake such an evaluation, the agency believes that such an evaluation is better suited to EPA, given EPA’s responsibility, regulatory authority, and expertise. The agency also noted that EPA is currently in the process of reviewing EPA’s regulations for the control of lead and copper in drinking water. CDC noted that the agency could provide technical assistance to EPA and would consider publishing an article after the EPA review is complete. However, publishing an article in the MMWR Recommendations and Reports on the latest findings regarding the relationship between BLLs and lead in water could be of assistance to EPA. Moreover, it would allow CDC, in a timely manner, to address any remaining confusion related to the health effects of lead in water in a venue targeted to CDC’s audience. Because CDC has not published an overview of the health effects of lead in water in the MMWR Recommendations and Reports, clinicians and state and local health officials who look to CDC for comprehensive information on public health issues may be uncertain about what is known and not known about the contribution of elevated lead levels in tap water to BLLs in children.

CDC Has Begun an Initiative and Revised Procedures to Help Ensure That CDC Information Is Accessible and Clear, but These Procedures Do Not Address Confusion after Publication

CDC officials told us they had begun an initiative and revised procedures to help ensure the accessibility and clarity of CDC public health communications prior to publication, both agencywide and in NCEH. Specifically, an official from the Office of the Director told us that the CDC Office of the Associate Director of Science has begun an initiative to revise existing procedures to help ensure that information that CDC publishes, such as guidelines and recommendations, is easily accessible by a common portal on CDC’s Web site. As of January 2011, CDC officials were still determining what type of CDC products and communication methods would be included in the initiative. In addition, CDC officials told us that NCEH, the center responsible for lead poisoning prevention programs and the 2004 MMWR article, had revised its clearance procedures for certain products, including those submitted to the MMWR, in an effort to ensure that the information presented is accurate and clear. CDC officials said that the revised NCEH clearance procedures are more rigorous and systematic and include requirements for additional peer review of some products, as well as review of some products by the Office of the Director, to help ensure that senior officials are aware of the products. For example, CDC documents that include major scientific findings or conclusions representing scientific breakthroughs or that directly contradict previous science that served as the basis for public health policy will be elevated to the Office of the Director for review. The officials said that the agency believes the initiative and revised procedures will help to mitigate the risk of other communications being subject to the type of confusion or misinterpretation surrounding the 2004 MMWR article. As of January 2011, CDC did not have time frames for completing the Office of the Director’s initiative.

Despite the agency’s current actions to strengthen review of CDC communications prior to publication, CDC officials said that neither the initiative nor the revised procedures will include actions to address confusion after publication. For example, if CDC becomes aware that information is being interpreted incorrectly, the procedures will not direct CDC staff to reach out to newspapers or other entities that have published the information to request corrections or clarifications. The importance of having procedures for this type of outreach was noted in the internal incident analysis, which stated that when CDC messages are not on target or are misinterpreted, such as happened in reaction to the 2004 MMWR article, CDC should respond in appropriate visible forums to publicly and expeditiously correct itself or correct those who are interpreting the message. Further, neither the initiative nor the revised procedures will include any postpublication review of certain types of communications that are similar to the 2004 MMWR article, such as those that are published in an expedited time frame and address urgent or high-profile issues, to determine whether corrections or clarifications are needed based on how the communications have been interpreted or used. Because CDC does not have procedures for addressing confusion after publication, the agency runs the risk that its staff will provide inconsistent responses to interpretations of its information that differ from what CDC intended.

Conclusions

Although CDC has taken some belated actions to clarify confusion related to the 2004 MMWR article on BLLs of residents in the District, the agency does not plan to publish a comprehensive review of the role of tap water as a source of lead exposure that would communicate what is known about the contribution of lead in water to elevated BLLs in children. A goal of the Healthy People 2020 initiative is to eliminate elevated BLLs in children. Although significant progress has been made in reducing lead exposure from lead-based paint and leaded gasoline, CDC has an opportunity to refocus its efforts toward accomplishing this Healthy People 2020 goal and to make a significant contribution to scientific literature by clearly describing what is known about the effect of lead in tap water on BLLs in children.

CDC’s credibility as the nation’s premier public health agency relies on presenting accurate, reliable, and timely information to the public. Information that is inaccurate or unclear in a CDC public health publication could result in confusion—such as resulted when some readers understood the 2004 MMWR article to state that elevated lead levels in tap water were not a concern in the District or in their area—and could undermine the agency’s credibility. The potential for presenting confusing information may increase when the agency has to respond quickly, as it did when it published the 2004 MMWR article 6 weeks after the DCDOH requested CDC’s assistance. When CDC presents potentially confusing information and does not respond in a timely or consistent fashion to clarify confusion following publication of a public health product, the agency runs the risk that an incorrect interpretation of the intended message could put the public at risk of adverse health effects, such as those that result from elevated water lead levels. CDC can mitigate the risk of such misinterpretations as well as the resulting risk to its credibility by developing procedures that allow it to address confusion in a timely, consistent manner.

Recommendations for Executive Action

We are recommending that the Director of CDC take two actions, the first to clarify confusion about the contribution of lead in tap water to elevated BLLs, and the second to improve the clarity of CDC’s published information on public health issues. 1. Publish an article in an MMWR Recommendations and Reports that conveys what is known and not known about tap water as a source of lead exposure and communicates the potential health effects in children of elevated lead levels in water in consultation with EPA, as appropriate. 2. Develop procedures to review previously published information and determine whether additional information should be published to help ensure the correct understanding of the public health message. The procedures could include criteria to use when deciding how to respond in certain situations, such as the event in the District, in which CDC learns of confusion about the public health message and determines that clarification or additional information should be published or CDC issues or releases a product in an expedited time frame or based on uncertain or incomplete information and determines additional information should be published to clarify the original public health message, even if there is no evidence of confusion.

Agency Comments

CDC reviewed a draft of this report and provided written comments, which are reprinted in appendix V. CDC generally concurred with our recommendations and submitted general comments on the draft.

CDC agreed with our first recommendation to publish an article in an MMWR Recommendations and Reports. While CDC previously stated that it had no plans to publish such an article, it stated in its written comments that it now plans to publish an article in an MMWR Recommendations and Reports that will focus on what is known about tap water as a source of lead exposure and summarize the potential health effects in children from lead exposures.

Related to our second recommendation to develop procedures to review previously published information and determine whether additional information should be published to help ensure the correct understanding of the public health message, CDC said it planned to adopt several procedures for taking action when the agency becomes aware of confusion about its message. CDC’s written comments indicated that these procedures will be effective when approved by the CDC Director. Specifically, CDC stated that when appropriate, it may take actions to address significant errors of understanding or perception resulting from public health information disseminated by the agency. For example, for errors of understanding or perception in which there is a persistent, broad, or otherwise significant misinterpretation of information in a public health product, CDC will present the scientific conclusions in clear language in several ways, such as a posting on the CDC Web site or by direct outreach to the news and electronic media, including via press releases or letters to the editor. However, within these procedures, CDC did not explicitly address situations where CDC issues or releases a product in an expedited time frame or based on uncertain or incomplete information and determines additional information should be published to clarify the original public health message, even if there is no evidence of confusion. It is important that CDC take this additional step in order to help ensure that the agency can address confusion in a timely manner and thereby mitigate risk to the public’s health or the agency’s credibility.

CDC also provided technical comments, which we incorporated as appropriate.

As agreed with your office, unless you publicly announce the contents of this report earlier, we plan no further distribution until 30 days from the report date. At that time, we will send copies to the Secretary of Health and Human Services and other interested parties. The report also will be available at no charge on the GAO Web site at http://www.gao.gov.

If you or your staff have any questions about this report, please contact me at (202) 512-7114 or at bascettac@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. Other major contributors to this report are listed in appendix VI.

Appendix I: 2004 Morbidity and Mortality Weekly Report Article about Blood Lead Levels of District Residents

On April 2, 2004, the Centers for Disease Control and Prevention (CDC) published the following article in the Morbidity and Mortality Weekly Report, which presented results of the investigation on the effect of lead in the District’s tap water on the blood lead levels of residents. Additionally, in 2010 CDC added the information contained in the box under the article’s title. The article is presented here in its electronic version, which was accessed from CDC’s Web site.

Appendix II: 2010 Letter Clarifying Information about the 2004 Morbidity and Mortality Weekly Report Article

On May 20, 2010, the Centers for Disease Control and Prevention (CDC) sent the following letter to state and local Childhood Lead Poisoning Prevention Program managers to address confusion related to the first sentence in the Editorial Note section of the 2004 Morbidity and Mortality Weekly Report article, which contained an incorrect statement. Additionally, the letter presented results of a recent analysis that included new blood lead level data that had not been available to CDC in 2004. The letter is presented here in its electronic version, which was accessed from CDC’s Web site.

Appendix III: May 21, 2010, Notice Clarifying Information about the 2004 Morbidity and Mortality Weekly Report Article

On May 21, 2010, the Centers for Disease Control and Prevention (CDC) published the following Notice to Readers in the Morbidity and Mortality Weekly Report (MMWR) to clarify information about the first sentence in the Editorial Note in the 2004 MMWR article and to present results of a recent analysis that included new blood lead level data that had not been available to CDC in 2004. The Notice to Readers is presented here in its electronic version, which was accessed from CDC’s Web site.

Appendix IV: June 25, 2010, Notice Clarifying Information about the 2004 Morbidity and Mortality Weekly Report Article

On June 25, 2010, the Centers for Disease Control and Prevention (CDC) published the following Notice to Readers in the Morbidity and Mortality Weekly Report (MMWR) that noted the limitations of the results of an analysis in the 2004 MMWR article. The Notice to Readers is presented here in its electronic version, which was accessed from CDC’s Web site.

Appendix V: Comments from the Centers for Disease Control and Prevention

Appendix VI: GAO Contact and Staff Acknowledgments

Staff Acknowledgments

In addition to the contact named above, Karen Doran, Assistant Director; April W. Brantley; Natalie Herzog; Amy C. Leone; Lisa Motley; and Roseanne Price made key contributions to this report.