Oct 8, 2010 (CIDRAP News) – The US Centers for Disease Control and Prevention (CDC) yesterday issued final estimates for last season's flu vaccine and the 2009 H1N1 monovalent vaccine, confirming a record number of flu vaccine doses distributed.
The CDC's report on the vaccines, published yesterday on its Web site, is a follow-up to preliminary and state-by-state coverage estimates that it issued in April.
The agency had anticipated that uptake of seasonal flu vaccine last fall and winter would be influenced by heightened interest in flu due to pandemic flu activity, which came with public health recommendations to get the seasonal vaccine early. Manufacturers rushed to roll out the seasonal flu vaccine to make way for the pandemic vaccine, which came more slowly and with fewer early doses than first projected.
The 2009-10 flu season was also the first full year that seasonal flu vaccines were formally recommended for all school-aged children.
Health officials are eager to see how a new universal flu vaccination recommendation for everyone age 6 months and older that takes effect this season will influence uptake levels for the coming flu season.
The CDC based its estimates for the two vaccines on two surveys, the Behavioral Risk Factor Surveillance System, an ongoing state-based phone survey of about 400,000 adults, and the National 2009 H1N1 Flu Survey (NHFS), which began last October and ended in June. It based its final estimates for the vaccines on vaccinations reported through May 2010 and interviews conducted through June.
Estimates are a little higher than previous projections for both vaccines because the data includes a broader vaccination period that extended through May 2010.
Seasonal flu vaccine patterns
For the seasonal vaccine, the CDC estimates that national coverage for all people ages 6 months and older was 41.2%, slightly higher than its earlier projection of 39.7% for the population as a whole. It said about 123 million people received the seasonal flu vaccine through May 2010, an increase from the previous estimate of 118.8 million.
Rates were highest for seniors at 69.6%, followed by adults between the ages of 50 and 64 (45%), children ages 6 months through 17 years (43.7%), younger adults with underlying conditions (38.2%), and healthy younger adults (28.4%).
The CDC cautioned that the seasonal flu vaccine coverage is an overestimate, because the reported coverage level of 123 million exceeds the 114 million doses of seasonal vaccine that were distributed. In its early estimate the CDC had said that respondent confusion over the two types of flu vaccines might have contributed to some overreporting.
Compared with the 2008-2009 flu season, coverage rates rose for all groups except for adults ages 50 through 64.
Pandemic flu vaccine findings
For the pandemic vaccine, the CDC estimates that national coverage for all groups was 27%, which is slightly higher than the April estimate of 24%. About 80.8 million people received the 2009 H1N1 vaccine, according to the latest estimate, compared with the earlier estimate of 72 million.
Coverage was highest in children ages 6 months through age 17 at 40.5% followed by seniors (28.9%), people ages 25 through 64 in high-risk groups (28.6%), and healthy people ages 25 through 64 (18.7%). Pandemic vaccine coverage was 34.2% in the CDC's initial target group: children, younger adults, people with underlying medical conditions, pregnant women, and healthcare workers.
The CDC said high uptake of the pandemic vaccine in children probably reflects the focus many states had on childhood vaccinations, the use of school-based vaccination clinics, and a recognition that children were at risk for severe disease.
Oct 7 CDC seasonal and pandemic flu vaccine report
Apr 29 CIDRAP News story "Seasonal flu vaccine uptake rose in 2009-10"
Apr 2 CIDRAP News story "CDC estimates 24% of Americans received H1N1 vaccine"