A couple of weeks ago I had my lovely elderly parents around for lunch. The subject of flu vaccination came up. My father is dead against this practice, and views flu as a largely self-limiting illness that rarely leads to significant complication (he’s right). My mother, on the other hand, has dutifully attended her doctor’s surgery for the last few years for her flu ‘shot’. Vaccination is, by her own admission, always followed by a persistent cough. This may be coincidence of course, or perhaps a ‘nocebo’ response (like a placebo response, only negative).
Anyway, I ended up suggesting she might rethink her views on the vaccination, especially in light of evidence which suggests that it does not particularly help the elderly (as it’s so often said to do). See here and here for more on this. The upshot is my mum skipped her flu shot this year.
Another reason why I’m not particularly enthusiastic about flu vaccination is that the ‘evidence base’ for it appears pretty flimsy. Last year, the British Medical Journal published a review of the literature which I wrote about here. Read this blog post and/or the original BMJ article and you may come to the conclusion that flu vaccination policy is based on misreporting and misrepresentation of the actual evidence.
I started to think about this topic again on receipt of an email yesterday from an US-based doctor who alerted me to this document. It is written by Dr Eric Kasowski, a doctor the US Center for Disease Control’s (CDC’s) Influenza Division. It urges healthcare workers to get their flu shots. Oddly, for something aimed at health professionals, it cites no studies. I don’t want to be overly suspicious, but this is usually not a good sign.
While we health professionals like to think of ourselves as independently-minded people, the fact is we are as subject to ‘group-think’ as anyone else, in my opinion. Do doctors really have time to go back to the original research, read it and assess it? Not usually. Normally, we doctors will accept what our Government’s tell us quite uncritically.
By way of example, let me relate an experience from a month or so ago. I was listening to the radio and the subject of flu vaccination was being discussed. The issue of the evidence for this practice came up. The doctor in the radio studio giving comment was not only unable to cite any evidence, he also stated that there MUST be evidence, otherwise our Government would not be advising that we have these shots. I’d like to say that such naivety was a rare thing in medicine, but my experience tells me that it is not.
Anyway, after talking with my parents I thought I’d take a look for any more recent evidence relevant to flu vaccination, and came across a review published earlier this year by the Cochrane Collaboration (a collective of international doctors and scientists supposedly dedicated to objective assessments of treatments by proper review of the evidence) . The authors of this review highlight the fact that industry-funded studies were more likely to report positive findings and be published in prestigious journals and be cited more frequently. Here’s the exact wording of the warning:
This review includes 15 out of 36 trials funded by industry (four had no funding declaration). An earlier systematic review of 274 influenza vaccine studies published up to 2007 found industry funded studies were published in more prestigious journals and cited more than other studies independently from methodological quality and size. Studies funded from public sources were significantly less likely to report conclusions favorable to the vaccines. The review showed that reliable evidence on influenza vaccines is thin but there is evidence of widespread manipulation of conclusions and spurious notoriety of the studies. The content and conclusions of this review should be interpreted in light of this finding.
One of the problems with flu vaccination is that it tends not to work at all well if the strains of flu in the vaccine do not match the strains of flu in the environment. Even when the match is perfect, 1 per cent of flu vaccinated individuals ends up with a infection, compared to 4 per cent of unvaccinated individuals. However, in partial matching of vaccine/infecting strains (which is usually how things are), these figures are 1 per cent and 2 per cent respectively. In other words, the true reduction in flu risk in the population is a mere 1 per cent.
Here’s some more findings from this study:
Influenzea vaccines have a modest effect in reducing influenza symptoms and working days lost
There is no evidence that they affect complications, such as pneumonia, or transmission.
Here’s a plain language summary of the study in the authors’ own words:
Over 200 viruses cause influenza and influenza-like illness which produce the same symptoms (fever, headache, aches and pains, cough and runny noses). Without laboratory tests, doctors cannot tell the two illnesses apart. Both last for days and rarely lead to death or serious illness. At best, vaccines might be effective against only influenza A and B, which represent about 10% of all circulating viruses. Each year, the World Health Organization recommends which viral strains should be included in vaccinations for the forthcoming season.
Authors of this review assessed all trials that compared vaccinated people with unvaccinated people. The combined results of these trials showed that under ideal conditions (vaccine completely matching circulating viral configuration) 33 healthy adults need to be vaccinated to avoid one set of influenza symptoms. In average conditions (partially matching vaccine) 100 people need to be vaccinated to avoid one set of influenza symptoms. Vaccine use did not affect the number of people hospitalised or working days lost but caused one case of Guillian-Barré syndrome (a major neurological condition leading to paralysis) for every one million vaccinations. Fifteen of the 36 trials were funded by vaccine companies and four had no funding declaration. 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.
When Governments and the doctors and scientists paid by them urge us to do things but do not cite appropriate evidence (as is the case with the recent missive from Dr Kosowski) I say beware. These folks may put a case that makes their case seem like a no-brainer. In reality, though, what is often going on here is that their hoping that individuals will not look at the evidence base, engage their brains and think for themselves.
1. Jefferson T, et al. Vaccines for preventing influenza in healthy adults (Review). Cochrane Database Syst Rev. 2010 Jul 7;(7):CD001269.