WASHINGTON — Despite the severe shortage of influenza vaccine this winter, the elderly, young children, and others at risk were able to find and receive shots, officials said at the National Immunization Conference sponsored by the Centers for Disease Control and Prevention.
Once it was known last October that Chiron Corp. would not be able to deliver its half of the nation's vaccine supply, the CDC immediately set up a special surveillance team to track where the vaccine was going and who received it, said Susan Chu, Ph.D., acting director of the agency's Office of Science Policy and Technology Transfer.
Seventeen new questions on the flu vaccine were added to the monthly Behavioral Risk Factor Surveillance System survey. From November 2004 to February 2005, 105,473 adults, and 35,106 children (by proxy) were interviewed, said Michael Link, Ph.D., of the CDC's behavioral survey branch.
And, in a change of pace designed to keep state and federal agencies on top of the shortage, data were submitted to CDC weekly, not monthly, and were analyzed within days, giving states new data every 12 days or so, Dr. Link said.
As of late March, the survey found that vaccines were received by 63.5% of respondents over age 65 years, 26% of 18- to 64-year-olds at high risk, and 36% of health care workers, said Gary Euler, Dr.P.H., of the CDC National Immunization Program's epidemiology and surveillance division. These figures were slightly higher than those gathered through January and reported in the CDC's Morbidity and Mortality Weekly Report. According to those data, 62.7% of those over aged 65 years, 25.5% of those with high- risk conditions aged 18-64 years, and 35.7% of health care workers received vaccinations (MMWR 2005;54:304-7).
Through February, among healthy Americans, 7.2% of those aged 18-49 years, and 17.3% of those 50-64 years said they had been vaccinated, compared with 6.9% and 16.5%, respectively, through January.
Of children aged 6-23 months, 52% received a vaccine (up from 48.4% through January), which was a high uptake rate, given that 2004 was the first year the CDC's Advisory Committee on Immunization Practices recommended adding the flu shot to routine immunizations, said Carolyn Bridges, M.D., an epidemiologist with the agency's influenza branch.
Dr. Euler said there was room for improvement, as the survey found that many parents said they did not get vaccines for their children because they did not think their children needed them.
The demand for vaccine among patients aged 65 years and older was mostly met, though there was some problem getting vaccine in early November, Dr. Euler said.
An audience member questioned whether some of the demand had been met in Canada. As part of the survey, patients were asked where they got a vaccine. So if they went to Canada, those data would be captured, though they have not been analyzed yet, Dr. Euler said.
Vaccination rates also varied from state to state. Preliminary data indicate that states with lower immunization coverage had a smaller vaccine supply. Further analysis of the variation and the entire flu database will be coming over the next 6 months, Dr. Link said.
The CDC researchers acknowledged that the survey was limited because it is self-reported information, and does not cover people who are institutionalized.
Dr. Bridges said the CDC currently is researching whether faster analysis of flu data helped states with their shot distribution and management. And, she said, since it was an expensive undertaking, it's not clear if it will be repeated next year, or only in times of pandemic or shortages.