The influenza virus, which causes the common flu, has a high mutation capacity, superior to that of the new coronavirus, responsible for Covid-19. As a result, there are numerous variations of the flu virus in circulation, which leads to the need to update vaccines every year.
Based on the analysis of global data on influenza surveillance, the World Health Organization (WHO) released, this Friday (25), the recommendation of the strains of the virus that should compose the immunizations for the next flu season in the hemisphere. North.
For this year, it was defined by the WHO that vaccines produced for 2022 and 2023 from chicken eggs, such as those from the Butantan Institute, must use the following strains:
- Influenza A/Victoria/2570/2019 (H1N1)pdm09
- Influenza A/Darwin/9/2021 (H3N2)
- Influenza B/Austria/1359417/2021 (B/Victoria strain)
The quadrivalent vaccines, which have four strains of the virus, have the same composition recommendation, with the addition of the B/Yagamata strain (this year: Phuket/3073/2013).
How are vaccine strains defined?
To define the composition of vaccines that will be applied in the coming seasons of influenza, the WHO holds meetings with an advisory group of experts twice a year. Meetings take place between months of February and March to deliberate on recommendations for the Northern Hemisphere and, in September, to the Southern Hemisphere.
During the conferences, researchers analyze surveillance data produced by National Influenza Centers (NICs), as well as information on the genetic characterization of viruses. The group also evaluates data on resistance to antiviral drugs, such as oseltamivir, and results on the effectiveness of the vaccine used in the current and previous seasons.
Based on the set of analyses, the WHO issues, at the end of the meetings, the recommendation of the strains that should compose the immunizing agent, based on the greater probability of circulation of viral lineages.
Flu outbreak in Brazil
In December 2021, several capital cities had a high incidence of flu cases. The unusual phenomenon, given that the virus circulates with greater intensity in the winter months, was associated with low flu vaccination coverage, the relaxation of the restriction measures adopted to prevent Covid-19 and the relaxation of respiratory etiquette, which includes the use of masks, hand hygiene and social distancing.
According to virologist Fernando Motta, from the Laboratory of Respiratory Viruses and Measles at Instituto Oswaldo Cruz (IOC/Fiocruz), influenza outbreaks were mainly associated with the “Darwin” lineage of the Influenza A (H3N2) virus, which was not included in the composition. of the current vaccines in use in the southern hemisphere. This explains, in part, the increase in cases in the country at the time.
This Friday, the Butantan Institute delivered the first batch of flu vaccines with the updated version based on the inclusion of the Darwin strain of the influenza A (H3N2) virus. In all, two million doses were delivered to the National Immunization Program (PNI) of the Ministry of Health.
According to the institute, 80 million doses should be delivered for the flu vaccination campaign by April.
Basic care helps prevent the flu
Source: CNN Brasil
