Friday, February 22, 2013

We’re doing it wrong—influenza vaccine edition

This prospective cohort study out of University of Michigan demonstrated that influenza vaccine didn’t protect against PCR-documented influenza illness, influenza transmission in households, or medically-attended influenza. Given the good match between vaccine and circulating viruses during the 2010-11 season, and given that the population studied was predominantly healthy young adults and children, these results are pretty shocking (even in the context of other underwhelming data on the effectiveness of influenza vaccination). As John Treanor and Peter Szilagyi opine in the excellent accompanying editorial, “the apparent failure of influenza vaccine under optimal conditions seen in this study is indeed troubling.”

One of the more intriguing findings of this study is that receipt of flu vaccine the previous year seemed to reduce the effectiveness of the vaccine, a finding that is not new. What struck me most after reading these two papers, though, was this statement in the editorial:
"It is frequently stated that evaluation of influenza vaccines in randomized controlled trials is “unethical”, but given that the effectiveness of the vaccine is unclear, the subjects in such studies are typically at extremely low risk of serious disease, and that effective antiviral therapy is available, perhaps this statement should be reconsidered."
When a vaccine’s effectiveness causes experts to consider a return to randomized controlled trials, it’s safe to say that the vaccine in question is pretty awful. We desperately need something better.

3 comments:

  1. Good thing we're firing healthcare workers who are unvaccinated. We simply cannot tolerate people who won't take an ineffective vaccine.

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  2. I wonder how many hospitals and other healthcare facilities will change their policies? Will be interesting to see how this evidence is incorporated into vaccination programs. My guess is that the current influenza season will reinforce the authors' findings.

    Fascinating that sequential annual vaccination seemed to reduce the effectiveness of the vaccine.

    Questions in need of answers: Does receiving influenza vaccine prevent severe illness, hospitalizations or deaths?

    The authors' case definition was "cough, fever or feverishness, nasal congestion, chills, headache, body aches or sore throat. This case definition was intended to facilitate collection of specimens from even mild illnesses" (Ohmit, et al., 2013).

    Reducing morbidity and mortality may still be good enough reasons to continue with an imperfect vaccine, albeit probably not as a mandate.

    Hope an improved vaccine comes soon.

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  3. What factors other than vaccination history separate the vaccinated vs. unvaccinated subsets in that study? Are people who estimate their own exposure rate to be higher (teachers, hospital workers, people with families in grade school, etc) more likely to get the vaccination?

    Unless the vaccinate vs. unvaccinated samples are proper matched pairs based on potentially biasing factors, this study is unimpressive. It may well be that the sample was properly developed but normally one would mention something like that in the abstract.

    The "unexpected findings" actually look like there is no effect and that things are somewhat random. There are two kinds of explanations for when your data go all random: 1) The null hypothesis is not being challenged and/or 2) The study is bonkers. Which is the case here?

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