Risk Factors for Improper Vaccine Storage and Handling in Private Provider Offices
Authors: Bell Karen N. , Hogue Carol J. R. , Manning Claudine , Kendal Alan P. 
Published: August 2004

Context.

Preventing loss of vaccine potency during storage and handling is increasingly important as new, more expensive vaccines are introduced, in at least 1 case requiring a different approach to storage. Little information is available about the extent to which staff in private physicians' offices meet quality assurance needs for vaccines or have the necessary equipment. Although the National Immunization Program at the Centers for Disease Control and Prevention (CDC) in 1997 developed a draft manual to promote reliable vaccine storage and to supplement published information already available from the CDC and the American Academy of Pediatrics, the best ways to improve vaccine storage and handling have not been defined.

Objectives.

To estimate the statewide prevalence of offices with suboptimal storage and handling, to identify the risk factors for suboptimal situations in the offices of private physicians, and to evaluate whether the distribution of a new National Immunization Program draft manual improved storage and handling practices.

Design.

Population-based survey, including site visits to a stratified, random sample of consenting private physicians' offices. At least 2 months before the site visits, nearly half (intervention group) of the offices were randomly selected to receive a draft CDC manual entitled, “Guideline for Vaccine Storage and Handling.” The remainder was considered the control group. Trained graduate students conducted site visits, all being blinded to whether offices were in the intervention or control groups. Each site visit included measurements of refrigerator and freezer temperatures with digital thermometers (Digi-thermo, Model 15-077-8B, Control Company, Friendswood, TX; specified accuracy ± 1°C). Their metal-tipped probes were left in the center shelf of cold storage compartments for at least 20 minutes to allow them to stabilize. The type of refrigerator/freezer unit, temperature-monitoring equipment, and records were noted, as were the locations of vaccines in refrigerator and freezer, and the presence of expired vaccines. Other information collected included the following: staff training, use of written guidelines, receipt of vaccine deliveries, management of problems, number of patients, type of office, type of medical specialty, and the professional educational level of the individual designated as vaccine coordinator.

Participants.

Two hundred twenty-one private physicians' offices known by the Georgia Immunization Program in 1997 to immunize children routinely with government-provided vaccines.

Outcome Measures.

Estimates (prevalence, 95% confidence interval [CI]) of immunization sites found to have a suboptimally stored vaccine at a single point in time, defined as: vaccine past expiration date, at a temperature of ≤1°C or ≥9°C in a refrigerator or ≥−14°C (recommended for varicella vaccine) in freezer, and odds ratios (ORs) for risk factors associated with outcomes. We performed χ2 analysis and Student's ttests to compare the administrative characteristics and quality assurance practices of offices with optimal vaccine storage with those with suboptimal storage, and to compare the proportion of offices with suboptimal storage practices in the groups that did and did not receive the CDC manual.

Results.

Statewide estimates of offices with at least 1 type of suboptimal vaccine storage included: freezer temperatures measuring ≥−14°C = 17% (95% CI: 10.98, 23.06); offices with refrigerator temperatures ≥9°C = 4.5% (95% CI: 1.08, 7.86); offices with expired vaccines = 9% (95% CI: 4.51, 13.37); and offices with at least 1 documented storage problem, 44% (95% CI: 35.79, 51.23). Major risk factors associated with vaccine storage outside recommended temperature ranges were: lack of thermometer in freezer (OR: 7.15; 95% CI: 3.46, 14.60); use of freezer compartment in small cold storage units (OR: 5.46; 95% CI = 2.70, 10.99); lack of thermometer in refrigerator (OR: 3.07; 95% CI: 1.15,8.20); and failure to maintain temperature log of freezer (OR: 2.70; 95% CI: 1.40, 5.23). Offices that adhered to daily temperature monitoring for all vaccine cold storage compartments, compared with those that did not, were 2 to 3 times more likely to assign this task to staff with higher levels of training, have received a recent visit from the state immunization program, and be affiliated with a hospital or have Federally Qualified Health Center status. In addition, sites using &gt;1 refrigerator/freezer for vaccine storage were more likely to have at least 1 cold storage compartment outside recommended temperature ranges. We found no significant differences in the data reported above between the intervention group (received copy of the draft manual) and the control group (did not receive copy of draft manual), even when controlling for the annual number of immunizations given or the type of office.

Conclusions.

Problems with vaccine storage are common and mainly relate to inadequate monitoring of cold storage units or use of freezer units in inappropriate, small refrigerator/freezer units. A modest outlay to purchase equipment and/or train staff could avoid these problems. These results support the following steps: 1) do not store frozen vaccines in freezer compartments in less than full-sized refrigerators (&lt;18 cu ft); 2) monitor temperatures in both the refrigerator and freezer compartments to ensure that setting the freezer compartment control to &lt;−15°C does not lower the refrigerator compartment to &lt;2°C and thereby freeze vaccines that may be damaged by such exposure; 3) prepare a written job description for the duties of vaccine coordinator; 4) review temperature-monitoring practices; 5) follow standard procedures when vaccine temperatures are out of range or a power outage occurs; 6) inventory and rotate vaccines in cold storage each time new vaccines are delivered; and 7) train all vaccine-handling staff in the above and ensure that all have access to the latest authoritative guidance on vaccine storage and that all understand the meaning of temperature range, negative temperatures, Celsius and Fahrenheit scales, and conversion.