ABSTRACT. 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 metaltipped 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. 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 >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 d...