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“Vaccine” is a medical term that is part of the vernacular. They are our childhood immunizations and the backbone of public health programmes at national and international level, in both rich and poor countries. They are the holy grail of research against the biggest infectious disease killers of our time, from malaria and HIV/AIDS to influenza, and, more recently swine flu. They are multi-billion dollar business to drug companies. The World Health Organisation defines a vaccine as “any preparation intended to produce immunity to a disease by stimulating the production of antibodies…..The most common method of administering vaccines is by injection.”

Vaccines have been used in the elderly for over 40 years to reduce the impact of influenza (or flu) in this part of the population that is at higher risk of complications and death from flu. In 2000, 40 out of 51 high-income or middle-income countries recommended flu vaccination for all persons aged 60 or 65 or older, with over 290 million doses of vaccine distributed worldwide in 2003. You would think that a health policy of that scale would be firmly grounded on scientific evidence. Well think again.

Because influenza vaccines are produced and tested using surrogate outcomes (antibody stimulation) ahead of each influenza "season", past performance is probably the only reliable way to predict future performance. A new Cochrane systematic review looked through over 40 years of experimental and non-experimental studies of effectiveness of flu vaccines, and found very poor evidence for effectiveness of flu vaccination in the elderly. Of the 75 studies included in their analysis, they found only one recent randomised controlled trial which used “real” outcomes (e.g. actual flu cases or deaths from flu), as opposed to surrogate outcomes (e.g. influenza antibodies). All other studies were of low quality and open to bias. Current flu vaccines prevented 45% of pneumonia cases, hospital admissions and flu-related deaths in long-term care facilities (for example, nursing homes), compared to 25% vaccine efficacy in community settings. Tom Jefferson, lead author of the review, said, “Our estimates are consistently below those usually quoted by economists and in decision making." He calls for “an adequately powered publicly-funded randomised placebo-controlled trial run over several seasons”, and emphasis on “strategies to complement vaccinations”, such as personal hygiene, food and water.

The current swine flu pandemic has caused renewed interest in influenza vaccines and their performance, and this timely review surely gives us lessons on why we should base global health policy on evidence, before spending billions of pounds, dollars and many other currencies. Perhaps the most cautionary part of this review is the analysis of study funding and quality. High quality studies were 16 times more likely to make conclusions that agreed with the presented results, and less likely to favour effectiveness of vaccines. Government-funded studies were less likely to have conclusions favouring vaccines. Studies published in prestigious journals that were most frequently cited were associated with partial or complete industry funding. How much more evidence do we need that profits are trumping public health and evidence when it comes to flu?

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