on the (non?)effectiveness of the flu vaccine
update: it was pointed out that in the original post i didn’t properly distinguish between the flu vaccine and tamiflu which is an anti-viral typically given after patient presents symptoms of the flu. while some people take the antiviral tamiflu prophylactically to prevent the flu it is not commonly prescribed by doctors as preventative treatment over getting the flu vaccine. i’ve edited the post accordingly, though it doesn’t change the overall conclusions that there is not much strong evidence that either is particularly effective at preventing catching or lessening the effects of the flu.
note: as you’re reading this try to remember that i’m not an anti-vaccine nut. i’m only writing about the flu vaccine. i also don’t feel the vaccine is particularly dangerous. i’m certainly not anti-science. i’m pro evidence-based medicine. if you think i’m wrong, feel free to provide evidence. i’m happy to consider it and update the post accordingly.
there’s no doubt that it’s a bad flu season, especially for the elderly, which of course, brings about nearly universal calls for the population to get the flu vaccine like this, “For God’s Sake, Go Get a Flu Shot”, which passingly mentions the effectiveness of the vaccine while the author laments, “some of the smartest people I know act in the most irrational ways” in choosing to not get vaccinated. some of the more nuanced articles like, “Don’t be selfish: Get a flu shot and protect the most vulnerable, bioethicist says”, admit that while it’s not particularly effective you should still get the vaccine to protect the herd. in other words, the ethics of getting the vaccine go beyond you and your selfish needs and it’s important not so much to protect you as it is to protect “…the newborn baby baby down the road…” (!)
but what does the actual, independent research say about the flu vaccine’s effectiveness at preventing infection, reducing the severity of symptoms once infected, preventing transmission and reducing overall morbidity and mortality? the renowned cochrane collaboration ( which performs systematic reviews of randomized controlled trials of health-care interventions and provides official recommendations to the world health organization ) released their review of “Vaccines for preventing inﬂuenza in healthy adults”. their “plain language summary” and conclusion is notable in how different it is in tone from the headlines:
“There is not enough evidence to decide whether routine vaccination to prevent inﬂuenza in healthy adults is effective…The results of this review seem to discourage the utilisation of
vaccination against inﬂuenza in healthy adults as a routine public
and they go futher in a companion summary
“Our results may be an optimistic estimate because company-sponsored influenza vaccines trials tend to produce results favorable to their products and some of the evidence comes from trials carried out in ideal viral circulation and matching conditions and because the harms evidence base is limited..”
the data is even less clear ( if that were even possible ) with tamiflu. the cochrane collaboration updated their review of unpublished flu vaccine trials last year and the results may surprise you. forbes of all places has a summary if you’re not motivated to read the whole thing, “The Myth of Tamiflu: 5 Things You Should Know”. to summarize their summary:
1. any effectiveness data ( marginal as it is ) you hear reported is possibly inflated by publication and reporting biases. 60% of randomized data from the tamiflu treatment trials have never been published.
2. The studies did not show that tamiflu reduced the risk of hospitalization.
3. The studies were inadequate to determine the effect of tamiflu on complications.
4. The studies were inadequate to determine if Tamiflu reduced transmission of the virus.
5. The use of Tamiflu did reduce the duration of symptoms by about a day.
the lack of conclusiveness was so pronounced and the potential for shenanigans with reporting bias was so great that the cochrane researchers asked roche for the original studies to make firm conclusions about the drug. would it surprise you learn that the drug company has not released the data?
so whenever you hear a news report on getting the flu vaccine or tamiflu, remember the thoughts of the cochrane collaborators after writing their review of the knowns and unknowns about the effectiveness of the vaccine:
“Despite the monumental task that the authors have completed, many uncertainties remain unresolved, and more have surfaced as a direct result of their efforts. The questions now raised by the review are, if anything, more thought-provoking than the answers it provides.”
relatedly, cochrane has previously reported that there is no evidence that only vaccinating healthcare workers prevents laboratory-proven influenza, pneumonia, and death from pneumonia in elderly residents.
finally, if you’re really interested in evidence-based medicine and reducing transmission of the flu, the university of michigan has showed that pairing masks and hand washing results in a 75 percent reduction in flu-like illness which is, as you might recall, more effective that the likely-to-be-biased flu vaccine research results. also, get a humidifier.
more interesting reading: “The Atlantic: Does the Vaccine Matter?” ( though i do think author conflates a few issues and i don’t agree with all her conclusions – i.e. i don’t agree with everything she writes. )