Flu vaccine may have less effective response due to circulating viruses – Observer

The flu vaccine may have a less effective response this year due to the difference between the flu viruses for which the vaccine was produced and those in circulation, according to the coordinator of the Réseau Médecins-Sentinelles.

“The viruses circulating in Portugal, which are mostly type A viruses, of the AH3 subtype, and those that have been analyzed as part of the influenza surveillance program, are antigenically distinct from those of the vaccine“, Public health doctor Ana Paula Rodrigues told the Lusa agency.

He noted, however, that doesn’t mean the vaccine isn’t working, there may be a diminished response.

“We do not yet have the data from the efficacy studies because there are not enough cases”, explained Dr. Ricardo Jorge (INSA) at a time when there is an upsurge in flu cases.


To explain this increase in cases, Ana Paula Rodrigues pointed out two winters in which practically the population did not come into contact with influenza viruses due to protection and containment measures, the easing of measures against Covid-19 and the “unseasonable cold” in March.

Although there is higher than usual flu virus circulation in March, it is not as high as in December, January and February, he said. , pointing out that Portugal will probably have “a flu epidemic later”. This year.”

But so far it has been similar to what has happened in previous winters, said Ana Paula Rodrigues, noting that people are also “more alert” to the onset of respiratory symptoms due to Covid-19.

there is also at that time tests that simultaneously screened for influenza and Covid-19therefore, “there is a greater knowledge of the community in general and also of health professionals of the occurrence of these cases”, he observed.

In the laboratory responsible for the epidemiological surveillance of influenza, virologist Raquel Guiomar added that at this point the epidemic period was already coming to an end.

“However, due to very reduced traffic over the past two years and other dynamics also put in place”, as well as the lifting of personal protective measures “the virus now has the possibility of being transmitted from person to person”said the virologist.

According to the head of the National Reference Laboratory for Influenza Virus and Other Respiratory Viruses, the “most susceptible” population to influenza virus infection in recent weeks has been children.

“It’s a new dynamics of respiratory viruses which must be monitored very closely because we know that these last two years of the pandemic have also interfered in some way with the circulation of the flu virus and other respiratory viruses”, he defended himself.

Raquel Guiomar pointed out that influenza has “a wide range of presentations and symptoms” and can present severe illness in at-risk populations.

For this reason, advanced the current goal is “to expand influenza surveillancenot only in the primary health care setting, but also to strengthen surveillance at the hospital level to also assess the impact on the health of the population and its association with more serious cases”.

Regarding the cases of co-infection with the influenza virus and SARS-CoV-2, Raquel Guiomar said that 33 cases have been detected in Portugal, but that “a greater severity of the disease has not been documented in these cases”.

This is a case that is being closely monitored because this situation of double infection is all the more frequent as the circulation of these two viruses is frequent, ”he underlined.

Asked about the date on which the surveillance of Covid-19 will be integrated into the influenza surveillance networks, the researchers explained that this adaptation is done in collaboration with other entities at the national level, in particular with the General Directorate of Health. .

“It is a work that is still in development. so that, at least, during the next winter, this integration can already be optimized and improved,” said Raquel Duarte.

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