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A Report Card for the Worrisome 2004–2005 Flu Vaccine
Even in a year of antigenic drift, both forms of influenza vaccine performed reasonably well.
Every February, a U.S. national committee selects the components of the influenza vaccine for the coming year. The vaccine for the 2004–2005 flu season turned out to be a poor match for circulating strains, which had drifted from the vaccine components. Two studies address this vaccine’s performance.
In a blinded, randomized study, 1041 healthy adults received either the inactivated (intramuscular) or the live attenuated (intranasal) vaccine in the fall of 2004. Compared with placebo recipients, those who received inactivated vaccine were significantly less likely to develop lab-confirmed influenza, with an overall vaccine efficacy of about 70% — similar to that seen in previous years. The live attenuated vaccine protected well against influenza A but not B, with an estimated overall efficacy of 30%.
In a second, industry-supported study, all healthy students at 11 elementary schools in four states were offered live attenuated influenza vaccine in the fall of 2004; 47% were vaccinated. Questionnaires indicated that there were significantly fewer cases of flu-like illness in both children and adults in households of students at these "vaccinated" schools than in control school households, where a similar proportion of adults but significantly fewer children had been vaccinated.
Comment: Every winter, some ask whether the flu vaccine is worth all the bother of obtaining and administering it. These findings suggest that even when vaccine and circulating strains are poorly matched, evidence indicates both vaccine efficacy and some herd immunity. Editorialists call for further studies of the precise strengths and weaknesses of each type of vaccine, calling "the substantial effort to produce and deliver influenza vaccine" unambiguously justified by both seasonal epidemics and potential pandemics.
— Abigail Zuger, MD
Published in Journal Watch General Medicine December 13, 2006
Citation(s):
Ohmit SE et al. Prevention of antigenically drifted influenza by inactivated and live attenuated vaccines. N Engl J Med 2006 Dec 14; 355:2513-22.
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- Medline abstract (Free)
King JC et al. Effectiveness of school-based influenza vaccination. N Engl J Med 2006 Dec 14; 355:2523-32.
- Original article (Subscription may be required)
- Medline abstract (Free)
Fukuda K and Kieny MP. Different approaches to influenza vaccination. N Engl J Med 2006 Dec 14; 355:2586-7.
- Original article (Subscription may be required)
- Medline abstract (Free)