May 9, 2012 (CIDRAP News) – Survey data from the Centers for Disease Control and Prevention (CDC) suggest that at the peak of the H1N1 influenza pandemic in the fall of 2009, Americans were more worried about seasonal flu than the pandemic virus, according to a study published in Influenza and Other Respiratory Viruses.
The study is an analysis of findings from the CDC's 2009 H1N1 Flu Survey, a telephone poll that targeted about 6,000 people per month from October 2009 through June 2010. Respondents were asked whether they had received pandemic H1N1 (pH1N1) and seasonal flu shots, their level of concern about getting sick if not vaccinated, their views on the vaccines' effectiveness, and their level of concern about getting sick from the pH1N1 vaccine.
"Surprisingly, our data found that the perception of risk from pH1N1 was lower than for seasonal influenza, even in October and November, and this perception of risk decreased after November," says the team of CDC investigators, with Tammy A. Santibanez, PhD, as first author.
Overall, 26.1% (95% confidence interval, plus or minus 0.9%) of respondents thought the chance of getting sick with pH1N1 if not vaccinated was "very high" or "somewhat high," compared with 38.5% (plus or minus 0.9%) for seasonal flu.
The report notes that pH1N1 was by far the dominant flu strain in the United States in October and November 2009. It says there was a big increase in demand for seasonal flu vaccine at that time, "which could indicate some confusion about what strains were included in the seasonal influenza vaccine and a mistaken belief the seasonal vaccine would provide protection from pH1N1."
In other findings, 74.0% (plus or minus 0.8%) thought the pH1N1 vaccine was very or somewhat effective, versus 80.6% (plus or minus 0.8%) for the seasonal vaccine. Also, respondents said they were more worried about getting sick from the pandemic vaccine than the seasonal shot, by 31.3% to 27.4% (each plus or minus 0.9%).
Many of the findings varied significantly with ethnicity, education, and income level. For example, more Hispanics (39.3%) than blacks (25.0%), whites (23.4%), and others (28.0%) thought they had a good chance of getting sick with pH1N1 if not vaccinated. At the same time, Hispanics were more likely than other groups to report being worried that the pH1N1 vaccine would make them sick.
For another example, college graduates were significantly less likely than high school graduates to think they stood a good chance of getting sick with either pandemic flu (23.4% versus 28.8%) or seasonal flu (38.0% versus 40.6%) if they weren't vaccinated.
The survey also showed that opinions about vaccine effectiveness and personal risk strongly influenced the likelihood of being vaccinated. Vaccine coverage ranged from 7% to 11% for those who believed both vaccine effectiveness and their risk of getting sick if unvaccinated to be low. For those who thought the opposite, vaccine coverage ranged from 50% to 53%.
Citing some study limitations, the authors caution that their findings are based on self-reporting and that vaccination status was not verified by checking medical records.
Santibanez TA, Singleton JA, Santibanez SS, et al. Socio-demographic differences in opinions about 2009 pandemic influenza A (H1N1) and seasonal influenza vaccination and disease among adults during the 2009-2010 influenza season. Influenza Other Respi Viruses 2012 (early online publication May 8) [Abstract]
CDC final estimates of pH1N1 and seasonal flu vaccine coverage in 2009-10