Winter is ahead: how effective are flu shots?

Almost every influential health expert encourages people to get a flu shot every fall as a mandatory protective measure ahead of flu season. "Forum" presents a column by a regular author Vox Julia Bellaz whether vaccination is effective.

I asked several respected — and well-informed — medical researchers about what they thought about annual vaccination. Their response stunned me. With a smile on their faces, they explained to me that the flu vaccine is not particularly effective. A paradoxical situation has arisen. It seemed that the two groups of specialists said completely different things. However, after a little of my own analysis, I think I understand something about what is happening.

It is true that flu vaccines are not as effective, at least, as it is presented to us with the use of certain evidence (and in most cases, this evidence is based on weak methodological work). But the disadvantages of vaccination are absolutely minimal, that is, flu vaccines can still be useful in terms of disease prevention and life saving. It is for this reason that health experts say it is necessary to vaccinate anyway.

WHO forecast

The flu vaccine has been our main protection against seasonal flu for over 60. Respiratory diseases are caused by influenza A and B viruses. The flu vaccine is designed to protect people from three or four strains of viruses A and B, which researchers believe will be most common in a given season and can cause fever, headache, cough and runny nose

The main challenge, however, is that the influenza virus is extremely unstable and constantly mutates. For this reason, pharmaceutical companies cannot create a single vaccine for all times. Each year, departmental agencies make their assumptions about the strains that may be the most dangerous. And it is not easy.

In February, the World Health Organization (WHO) presents its forecast - based on observations and laboratory and clinical studies - and then each country individually follows these guidelines within its own jurisdiction (in the USA, the last word for the Food Safety Authority and medicines).

Any potential error can significantly affect the effectiveness of flu shots in a particular season. If vaccine manufacturers prepare for one combination of viruses, and they eventually transform into some other, the vaccine will not be as effective as expected. This, in many respects, explains the fact that data on the effectiveness of vaccinations often differ.

Differences in children and adults

The independent non-profit project Cochrane Collaboration, which addresses various medical issues, analyzed the effect of flu shots on healthy children and adults.

In the case of children, the vaccine turned out to work quite well. On average, vaccinating six children under age 6 can prevent at least one case of influenza. For children under 2 years of age, the benefit is less clear—the evidence the researchers found was extremely sparse.

Among adults, however, the vaccine's effectiveness is more modest. “It all depends on the season,” explains Tom Jefferson, a project fellow at the Cochrane Collaboration. “In any case, you need to vaccinate from 33 to 100 people to avoid one set of symptoms.” These data indicate that in years when the WHO is accurate with its forecast and the vaccine matches the strains of emerging viruses, vaccination will prevent the disease in every 33rd person vaccinated. And in the year when the WHO is wrong with its forecast, 100 people will need to be vaccinated so that at least one of them does not get the flu.

Jefferson also noted that the analysis conducted among adults showed that the level of influenza vaccination has virtually no effect on the number of hospital admissions and is completely unrelated to hospital admission rates.

"Millions of Lives"

It turns out that the vaccine can prevent the disease, but it is rather difficult to understand how it affects the health of the population from the point of view of statistics. On the other hand, experience shows that vaccination bears no harm. With the exception of cases of discomfort at the injection site, no side effects of vaccination have been identified.

“Overall, the flu vaccine is effective and saves lives. I can’t give an exact figure, but it could well be millions of lives,” scientist John Ioannidis of Stanford University told me. “This is a safe and fairly cheap procedure, so even if the effectiveness of vaccination is sometimes less than optimal, it is worth doing.”

In addition, there are very few alternative solutions. Apart from personal hygiene measures (clean hands or, for example, the need to stay home and not go to work when you are unwell), flu vaccine is the best medical way to prevent illness.

Bottom line: quite a few drawbacks with potentially significant benefits. Personally, I will continue to vaccinate for this reason.

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As Forum reported, last winter in the United States was marked by a real flu epidemic. The Center for Disease Control said at the time that the virus had mutated, and therefore last year’s vaccine could not provide 100% protection. However, doctors still called citizens (especially the elderly) get vaccinated. The strain of influenza H3N2, which became the main problem of last season, led to the deaths of several dozen people in different states.