Story at a glance
- Flu vaccines are reformulated annually to try to match the strains that are circulating.
- A preliminary study suggests part of this year’s flu shot may be less effective than expected.
- Experts are saying it is still effective in preventing severe disease and hospitalizations.
This winter, the coronavirus and flu viruses are expected to infect many people, sometimes simultaneously. Some health experts are saying that this year’s flu shot is poorly matched to the strain that is circulating. Others say it is still too early to know.
The annual flu vaccine, which takes months to produce, changes formulas every year according to what scientists predict will be the main influenza strain. Because of the way the virus is structured and can mutate, there are many combinations of parts that could make the flu virus different. For example, the strains of influenza are named by their H section and N section, like H1N1. Furthermore, there can be variations within a strain, such as there are many types of H1N1 viruses.
To get enough vaccine produced on time, the scientists must make a prediction as early as six months before the shots need to be delivered. As a result, the prediction for which strain will become popular could be wrong and that could lead to a less effective vaccination campaign.
This year’s flu shot is meant to protect against four strains of influenza. But one version of the H3N2 strain may be turning out to be a bad match against its out-in-the-wild version, reports NBC. This is based on a preprint study that has not been peer-reviewed yet.
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In the study, researchers test antibodies resulting from the flu shot against the new H3N2 strain. They found that the antibodies perform poorly at neutralizing the virus. They also conducted experiments to test the binding capabilities of the virus and conclude that this strain would be able to efficiently replicate in human bodies.
With the coronavirus, although it is mutating and developing into new variants, the part of the virus that is targeted by the vaccines has stayed consistent enough for the vaccine to remain effective in preventing severe illness. It would take more mutations for it to be so changed that the current available vaccines become ineffective. If that section of the virus does mutate so that it “escapes” the vaccines, the vaccine makers are ready to adjust the vaccines to be a better match.
For the flu shot, though it may contain one mismatched strain, it may still do its job.
“Influenza vaccination is the best protection against severe disease and illness,” said study author Scott Hensley, professor of microbiology at the University of Pennsylvania, to NBC. “Even in these years of mismatch, we see high effectiveness against hospitalizations and severe disease.”
Another expert who was not involved in the study agrees that the flu shot may still show that it is effective.
“This is very early to say that the current flu vaccine is not working. Even if we have one or two strains within the vaccine that is not the perfect match,” said Nicholas Haddad at the CMU College of Medicine to WNEM.
Another study published in the journal Proceedings of the National Academy of Sciences suggests that flu shots and other vaccinations like for measles could have indirect benefits in fighting against COVID-19. A team of researchers modeled the potential effects of other vaccinations on reducing hospitalizations and deaths and found that it could reduce the overall burden in a meaningful way.
This year’s uptake rate for the flu vaccine seems to be lower than previous years, especially in older people.
“I would advise people to embrace it. The effectiveness is defined by preventing disease severity or hospitalization or even death,” said Haddad. “We know for the past ten years, on average, the influenza vaccination has prevented around 40,000 deaths per year.”
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