Influenza A (H1N1) 2009 monovalent vaccination among adults with asthma, U.S., 2010

The 2009 pandemic influenza A (H1N1) virus (2009 H1N1) was first identified in April 2009 and quickly spread around the world. The first doses of influenza A (H1N1) 2009 monovalent vaccine (2009 H1N1 vaccine) became available in the U.S. in early October 2009. Because people with asthma are at increased risk of complications from influenza, people with asthma were included among the initial prioritized groups.

To evaluate 2009 H1N1 vaccination coverage and identify factors independently associated with vaccination among adults with asthma in the U.S.

Data from the 2009-2010 BRFSS (Behavioral Risk Factor Surveillance System) influenza supplemental survey were used; responses from March through June 2010 were analyzed to estimate vaccination levels of 2009 H1N1 vaccine among respondents aged 25-64 years with asthma. Multivariable logistic regression and predictive marginal models were performed to identify factors independently associated with vaccination.

Among adults aged 25-64 years with asthma, 25.5% (95% CI=23.9%, 27.2%) received the 2009 H1N1 vaccination. Vaccination coverage ranged from 9.9% (95% CI=6.4%, 15.1%) in Mississippi to 46.1% (95% CI=33.3%, 61.2%) in Maine. Characteristics independently associated with an increased likelihood of vaccination among adults with asthma were as follows: had a primary doctor, had other high-risk conditions, and received seasonal influenza vaccination in the 2009-2010 season.

Vaccination coverage among adults aged 25-64 years with asthma was only 25.5% and varied widely by state and demographic characteristics. National and state-specific 2009 H1N1 vaccination coverage data for adults with asthma are useful for evaluating the vaccination campaign and for planning and implementing strategies for increasing vaccination coverage in possible future pandemics.