Understand Why Flu Vaccine Has Little Effect On Current Epidemic

Darwin, a variant of the H3N2 influenza, is responsible for the off-season flu epidemic in São Paulo, Rio de Janeiro, among other states. The problem is that current flu vaccines are not prepared to face this strain, so it’s no use rushing to get vaccinated now thinking about protection against this mutation.

Still, experts say, getting the vaccine is a good way to be prepared for other threats. In addition to the individual benefit, avoiding illness is a way to contribute to alleviating the demand for care in health services.

Constant mutations in flu viruses — the most common in the world — that lead to new variants are absolutely common. Consequently, there is a need to update vaccines against influenza.

For this reason, the WHO (World Health Organization) constantly monitors the influenza virus variants that are in circulation and, twice a year, recommends which changes in the vaccines should be.

At the end of September this year, the WHO recommended that the Darwin variant (name of the Australian city in which it was identified) be part of the composition of influenza vaccines used in the south of the planet for the 2022 flu season. question: 2022.

An outbreak of flu in December 2021, close to the hot Brazilian summer, was not something to be expected. “Respiratory viruses like cold and dry weather”, says Renato Kfouri, pediatrician and director of SBIm (Brazilian Society of Immunizations).

​Therefore, the vaccines still available in 2021, which at the moment are mainly found in the private sector, considering that the vaccination campaign by the SUS has officially ended, do not include Darwin.

But, in any case, says Kfouri, they can help, even more considering the various other strains of influenza that make up the vaccine.

According to Isabella Ballalai, vice president of SBIm, there is a possibility of cross-protection, although the effect is likely to be small. The specialist says that there is an intense search for vaccines in Rio de Janeiro, where the influenza epidemic has started a long time ago.

“There are a lot of cases. The emergencies are full,” says Ballalai.

The specialist emphasizes that whoever gets the flu vaccine now —remembering, once again, that it will probably have little effect against the Darwin variant — is not exempt from being vaccinated against influenza next year. The other dose is required due to composition updates.

The populations most vulnerable to influenza are children under the age of five, the elderly, pregnant women and people with chronic health problems or compromised immune systems. Therefore, these are the populations that are usually targeted by vaccination campaigns.

The explanation for the influenza epidemic is not yet clear, say experts consulted by leaf. But some points must be taken into account.

One of them is the low vaccination coverage against the flu this year (despite the small effect of cross-protection). In addition, flu shots protect well for up to four months. After six months there is a considerable drop in protection. In other words, as this year’s vaccination campaign started in April, protection may already be greatly reduced now.

The behavioral factor amid the reduced circulation of Sars-CoV-2 also enters into this account. With fewer cases and deaths in the country, restrictions have been and continue to be relaxed.

In São Paulo, for example, the end of mandatory masks in open public places was already scheduled, a measure that was only suspended with the appearance of the ômicron variant of Covid and the proximity of the end-of-year parties.

With fewer restrictions, people started to circulate more and to promote meetings without masks.

“The only rational argument we can come up with is: people coming out of a ‘barren’ world, susceptible [à nova variante], not vaccinated”, says Ballalai, who adds that the virus circulates throughout the year in the country.

According to the WHO, in tropical regions, influenza can occur at any time of the year, with more irregular outbreaks than those observed in temperate areas.

Finally, according to Kfouri, possible competition between viruses could also eventually explain the flu outbreak at a time of Covid’s downturn.

Ballalai also points out that other virus infections have also increased recently and outside the standard seasonality. One of the examples is the syncytial virus, the main factor in hospitalization among children.