Flu outbreak arrives in São Paulo with virus that escapes the vaccine

The influenza A H3N2 virus, the same one associated with the Rio de Janeiro flu epidemic, is circulating in the city of São Paulo and is already causing an increase in emergency room visits and hospitalizations.

According to infectologist Nancy Bellei, professor at Unifesp and coordinator of testing at Hospital São Paulo, between Monday (13) and Tuesday (14), there are already nine people hospitalized with H3N2. In one week, there are already 19 cases of admissions. Last year, from March to June, the flu peak period, there were 12 cases.

“We are in an H3N2 epidemic, I have no doubts about that. In the office, I am treating several cases, my daughter had it, several of her friends had it”, says the doctor.

Virologist Celso Granato, clinical director of Grupo Fleury, also says he has increased the diagnosis of H3N2 in the analyzed samples, but he still doesn’t have a closed number. “That’s what happened in Rio. There, the positivity in exams increased tenfold. Now it’s getting here.”

Although the flu vaccine used in the immunization program has the H3N2 strain in its composition, it is not the same one currently circulating in Rio and São Paulo. This one, called Darwin [cidade na Austrália onde ela foi identificada pela primeira vez], is not covered by the current vaccine.

“Every year we change the vaccine recipe [contra o H3N2]. For 2022, WHO has already changed. It will be influenza A H3N2 Darwin. It is the strain that Fiocruz identified in the outbreak in Rio”, explains Nancy Bellei.

Celso Granato says that, even if the vaccine had the Darwin strain, the immunization against respiratory virus does not last more than six months. “It’s an untimely outbreak. We don’t have an outbreak in December. It all put together: the vaccine that doesn’t protect much, people took it for more than six months and people are no longer wearing masks, they’re crowding.”

Both Granato and Bellei say the best thing to do is for people to continue wearing masks and avoiding crowding.

“From a biological point of view, it’s not worth guiding people to revaccinate themselves. It’s worth using a mask, keeping your distance. These are the same recommendations as Covid,” says the doctor.

“Wearing masks and washing hands are the universal vaccines. Why didn’t we have the flu last year? Because people wore masks,” says Granato.

The main differences between the viruses, according to Bellei, is that the lethality of H3N2 is lower than that of Covid, comparing the same risk groups.

But the clinical symptoms of influenza, even if mild, are worse than those of mild Covid. “The patient has a high fever, chills, severe myia and headache, malaise, has no appetite, can’t get out of bed. Most of Covid’s mild cases don’t have that.”