The flu virus seems to be gaining ground in several countries in the Northern Hemisphere. In an article published on October 6, 2026, the journal Nature reports unusual traffic for this time of year. But should we be worried, as the vaccination campaign begins today?
Flu: early signals observed abroad
The study is clear and shows an already established presence in the Northern Hemisphere. In the United Kingdom and the west coast of the United States, the proportion of positive tests is already abnormally high. In Japan, outbreaks that appeared in August and early September even led to the closure of certain schools.
Another element monitored by researchers: the H1N1 subtype currently predominates among the cases recorded in the United States, while H3N2 was the majority the previous season.
And in France? The situation remains different for the moment.
“Influenza circulation remains moderate and the epidemic has not started in France, unlike in the United States”specifies Dr. Gérald Kierzek.
These observations justify particular vigilance, but do not yet make it possible to precisely predict the timetable or the scale of the next French epidemic.
Why is the G155E mutation in H1N1 worrying?
But scientists are particularly interested in a mutation of the H1N1 virus, called G155E. Virologists at the University of Washington in Seattle detected it in 13 of 17 samples analyzed in their laboratory.
Why does this mutation attract their attention? Because the first analyzes suggest a situation that could pose a problem:
“Strains carrying the G155E mutation are less well recognized by pre-existing antibodies”explains Dr. Gérald Kierzek.
The results seem particularly marked among adolescents and young adults. One hypothesis put forward by the researchers is that these people were less exposed, during their lives, to H1N1 viruses with similar characteristics.
“There could therefore be an erosion of immunity to certain strains, including in people already vaccinated or infected,” underlines the doctor.
This possibility is worth investigating, but it must be interpreted with caution. The available data is still based on a limited number of cases. They demonstrate neither a disappearance of immune protection nor an increase in the severity of infections.
Will an earlier flu necessarily be more virulent?
Not necessarily. Early circulation does not automatically mean that serious forms will be more numerous.
“An early start does not necessarily imply a more virulent season“, recalls Dr. Gérald Kierzek.
It is indeed necessary to distinguish the ability of a virus to be less well recognized by certain antibodies from its ability to cause serious forms. At the moment, scientists do not have enough data to determine the consequences of the G155E mutation over the entire flu season.
The progression of the different variants, their transmission and their consequences on infected people will have to be monitored over the coming weeks.
Flu vaccination: why you shouldn’t wait
Fortunately in France, the vaccination campaign against seasonal flu begins on October 13, 2026, at the same time as that against Covid-19. However, it takes approximately two weeks after the injection to develop sufficient immune protection.
“If the virus is circulating earlier than expected, getting vaccinated from the start of the campaign makes perfect sense,” advises Dr. Gérald Kierzek.
But could the G155E mutation reduce the effectiveness of the vaccine? This is one of the questions raised by the first analyses. However, imperfect protection does not mean that vaccination is no longer useful.
“Even if the vaccine does not perfectly match the strains circulating, vaccination remains useful“, insists the doctor.
It can help reduce the risk of infection, but also the severity of symptoms, complications and hospitalizations. This is particularly important for the most vulnerable people, who are more exposed to severe forms of the flu.
Who should get vaccinated now?
Vaccination is particularly recommended for people aged 65 and over, pregnant women, people with certain chronic illnesses and immunocompromised people. Health professionals and people in regular contact with vulnerable people are also concerned according to the recommendations in force.
“Eligible people have no reason to wait”recalls Dr. Gérald Kierzek.
For those concerned, the flu vaccine is 100% covered by Health Insurance upon presentation of the voucher, according to the terms provided. Vaccinations against flu and Covid-19 can be carried out on the same day, in two different arms.
This year, specific vaccines are favored for people aged 65 and over: Efluelda, at a high dose, and Fluad, which contains an adjuvant. These formulations aim to strengthen the immune response in elderly people, who are more exposed to complications from the flu.
In practice, the message from Dr. Gérald Kierzek is clear: no panic in the face of these first signals, but no unnecessary hesitation to get vaccinated when recommended. The French situation remains to be monitored, and vaccination remains an essential means of preventing complications from the flu.