This article uses technical terms. The basic terms, especially concerning the nomenclature of vaccines, are explained here.
Influenza viruses responsible for seasonal flu have the property of mutating easily, particularly those of type A and to a lesser extent those of type B. Every year, new viruses appear. These developments must be taken into account (we speak of antigenic drift) and the composition of influenza vaccines must be adapted accordingly so that they are as effective as possible.
As every year, during the month of February, the World Health Organization (WHO) defined the composition of the 2022-2023 influenza vaccines for the northern hemisphere (see the new 18857 you 25 March 2022).
The WHO, in the Weekly epidemiological report of October 28, 2022has just clarified the recommended composition of quadrivalent and trivalent influenza vaccines for the 2023 influenza season in the Southern Hemisphere.
1. Composition of the 2022 vaccine for the southern hemisphere: a new strain compared to the previous year
Antigenic analysis of circulating strains from the influenza season led WHO experts to modify the composition of the influenza vaccine for the 2022 southern hemisphere season. The A(H1N1)pdm09 strain has been updated.
The quadrivalent vaccines containing viruses prepared in eggs (the most common way of culturing the virus before extracting the vaccine antigens) will thus have to contain the following four influenza viruses (in bold new viruses compared to the previous season in the southern hemisphere):
- un virus de type A/Sydney/5/2021 (H1N1)pdm09 ;
- virus de type A/Darwin/9/2021 (H3N2) ;
- B/Austria/1359417/2021-like virus (B/Victoria lineage);
- B/Phuket/3073/2013-like virus (B/Yamagata lineage).
Compared to this year’s Southern Hemisphere vaccine, the virus A/Sydney/5/2021 (H1N1)pdm09 remplace le virus A/Victoria/2570/2019 (H1N1)pdm09.
Compared to the Northern Hemisphere vaccine, whose use in the context of the 2022-2023 winter campaign has just started on October 18, 2022, the A/Sydney/5/2021 (H1N1)pdm09 virus replaces the A/Victoria/2570/2019 (H1N1)pdm09.
The vaccines containing viruses prepared in cell culture or recombinant (recombinant proteins are obtained by genetic engineering) will have a slightly different composition: instead of including virus type A/Darwin/9/2021 (H3N2), these vaccines must contain the virus /Darwin/6/2021 (H3N2).
The trivalent vaccines are no longer used in France today. These vaccines contain only one type B virus: the WHO has specified that it will be the type B/Austria/1359417/2021 virus (B/Victoria lineage) for the next trivalent vaccines in the southern hemisphere.
2. Vaccination campaign
The influenza vaccination campaign for mainland France and the overseas departments-regions of the Americas (Martinique, Guadeloupe, Guyana) is that of the northern hemisphere.
Since the 2020-2021 season, given the particular epidemiology observed for several years in Mayotte, the vaccination campaign once morest seasonal influenza in Mayotte has been modeled on that of the northern hemisphere and uses the same vaccines. The vaccination campaign is initiated early in this territory, if possible in September and as soon as the flu vaccines are available.
The flu vaccination campaign for Reunion is that of the southern hemisphere and begins in April. The vaccines used during the next vaccination campaign in Reunion will therefore have this new composition.
In France, the influenza vaccination campaign began on October 18, 2022 with vaccines whose composition had been announced in March 2022in association with the booster vaccination campaign for covid 19.
Source: World Health Organization.
