The Department of Health and Human Service Office of the Inspector General's report -- Vaccines for Children Program: Vulnerabilities in Vaccine Management -- said a study conducted in April and May of 2011 looked at 45 providers in five states and cities. The program provides millions of free vaccines at 44,000 participating provider sites in all states and territories.
Investigators logged temperatures in vaccine storage units for two weeks and found there were times when vaccine was exposed to inappropriate temperatures for at least 5 cumulative hours in 76 percent of provider offices, during the two-week study period, the report said.
Thirteen of the 45 providers had expired vaccine stored alongside unexpired vaccine, with the majority of expired vaccine doses being seasonal influenza vaccine.
It was unlikely such doses were administered, the report said.
"The Centers for Disease Control is not recommending that parents revaccinate their children. The main concern with improper storage temperatures is that they can make vaccines less effective rather than less safe," the report said. "The study did not assess vaccine potency or effectiveness. While it is possible that some children have received less potent vaccines due to exposure to improper temperatures, our data do not suggest that this is a common or widespread problem. Our national monitoring indicates vaccines are doing their job at providing protection against disease."