Australia’s worst winter in memory. Calls for vaccination “urgently” in the United Kingdom and from European community organizations. Tokyo issues its first alert since 2009 and closes more than a thousand schools due to influenza.
in spain, Winter respiratory viruses crossed the epidemic threshold at the end of September, weeks earlier than usualThe number of cases reported last week has already doubled at this time.
The emergence of a new strain of the disease has put health authorities around the world on the wrong foot, calling on people at risk to get vaccinated as soon as possible.
It is a subclass of the H3N2 strain, initially known as J.2.4.1 and later just K, which has accumulated seven mutations that distinguish it from its closest relatives.
During the winter virus season, three main strains spread. Two of them are type A: H1N1, the heir to the 2009 pandemic that was most widespread last winter, and H3N2.
The other strain belongs to type B and, in principle, is usually more benign than type A.
According to the latest data from the Acute Respiratory Infection Surveillance System of the Carlos III Health Institute, the incidence of influenza in primary care in one week rose by 38.5%, reaching 33.1 cases per 100,000 inhabitants.
Of the samples obtained in the past seven days, 70 belong to H3 strains and 24 belong to H1 strains (an additional 32 samples were not classified into substrains).
He explains that the spread of the H3N2 virus contrasts with the spread of the H1N1 virus in recent seasons Diego Garcia Martinez de ArtolaSpokesman for the Spanish Society of Infectious Diseases and Clinical Microbiology (Seimc).
“The immunity we were generating from H1N1 infection, even if it was low-level, provided some protection,” he told EL ESPAÑOL.
“If there was a little bit of H3N2 in previous seasons, We do not have that previously generated immunity, even if it was at a low level“.
“You have to get vaccinated.”
This is especially important in children, because they are the main carriers of influenza, who “usually bring it into homes.” Because they are young, they have not had the opportunity to become infected and gain immunity to the H3N2 virus, which has a wide range of effects.
This lack of prior immunity will not be the only reason why the strain causes a large number of cases.
“Previously, the main champion of winter viruses was respiratory syncytial virus, or RSV. With the arrival of nirsevimab we started to ‘remove’ it from the market, so there could be more scope for influenza infections.”
For this reason, “people who are susceptible to influenza should get vaccinated against influenza: we may not avoid all cases, but we will avoid the most serious cases.”
At this point, it’s not all bad news. The first laboratory analyzes of the effectiveness of influenza vaccines against the new strain of H3N2 virus were not very encouraging.
However, real-world analyzes have shown that current vaccines are largely effective in preventing severe disease.
A study of the impact of H3N2 subtype K in the UK throughout the first month of autumn suggests that the vaccine stopped between 72 and 75% of hospital admissions for influenza A (both H1N1 and H3N2) in children aged 2 to 17 years.
The results are not optimistic for adults. The effectiveness of the vaccine will decrease to 32-39% compared to type A.
Fortunately, if we consider only the H3N2 strain (which accounted for 84% of all cases in adults aged 18 to 65 in the study), it rises to 60%.
“Laboratory tests tell us that it has a weak reaction against subclass K due to its additional mutations, but the first analyzes such as the one conducted in the United Kingdom make us believe that the vaccine continues to protect,” says García Martínez de Artola.
Authors of work published in the journal Euro controlHe cautioned that this effectiveness may fade as time passes since a person has been vaccinated.
However, Seimc spokesperson mentions this The strains that emerge at the beginning of winter are not the same as those that usually prevail at the end.
“This happens every season. In recent seasons, the pandemic variant (from 2009) has taken over with a new strain, and eventually other cases usually occur.”
Although the vaccine protects against severe forms of the disease, coverage is not perfect.
According to the grip barometer of the pharmaceutical company Sanofi, based on telephone surveys in different waves, half of those over 65 years old in our country have already received their dose.
Only three communities (Galicia, Basque Country, and Castilla y León) will have coverage of more than 55%, while Cantabria, the Balearic Islands and the Canary Islands will have less than 45%.
As for the age group between 60 and 64 years, the national total is much lower, at 20.3%. The vaccine is also recommended for boys and girls aged 6 to 59 months, but there are insufficient data to estimate coverage.