#16,602
Twice each year international influenza experts meet to discuss recent developments in human and animal influenza viruses around the world, and to decide on the composition of the next influenza season’s flu vaccine. Due to the time it takes to manufacture and distribute a vaccine, decisions on which strains to include must be made six months in advance.
Which means the composition of the northern hemisphere’s vaccine must be decided upon in February of each year, while decisions on the southern hemisphere’ vaccine are made in September.
We saw a similar scenario unfold with last fall's vaccine (see Preprint: Antigenic & Virological properties of an H3N2 Variant That Will Likely Dominate the 2021-2022 Influenza season), although its impact has been limited by this year's short-lived flu season
Two years into the coronavirus pandemic, and the job is even tougher. Influenza activity has been greatly diminished globally for the past two flu seasons, due to `viral interference' from COVID, and the social distancing and NPIs used to fight the pandemic. As a result, far fewer flu samples have been sequenced.
The WHO describes COVID's impact on their vaccine decisions in their FAQ.
18. How has the COVID-19 pandemic impacted the 2022-2023 northern hemisphere influenza vaccine recommendation?The volume of data available from recently circulating influenza viruses and the geographic representation have been lower for this northern hemisphere vaccine recommendation meeting than was typical prior to the COVID-19 pandemic. The reduced number of characterised viruses raises uncertainties regarding the full extent of the genetic and antigenic diversity of currently circulating influenza viruses and those likely to pose a threat in forthcoming seasons. Nevertheless, some groups of A(H3N2) and B/Victoria-lineage viruses have expanded and spread internationally during the current period. Consequently, the A(H3N2) and B/Victoria lineage component recommendations have been changed from the previous northern hemisphere recommendation.
Despite the level of uncertainty, decisions must be made, and yesterday's recommendations - which are very much in line with this year's (yet to be deployed) Southern Hemisphere vaccine - were released by the WHO.
25 February 2022
News release
Reading time: 1 min (271 words)
The World Health Organization (WHO) today announced the recommendations for the viral composition of influenza vaccines for the 2022-2023 influenza season in the northern hemisphere. The announcement was made at an information session at the end of a 4-day Information Meeting on the Composition of Influenza Virus Vaccines, a meeting that is held twice annually.
The WHO organizes these consultations with an advisory group of experts gathered from WHO Collaboration Centres and WHO Essential Regulatory Laboratories to analyse influenza virus surveillance data generated by the WHO Global Influenza Surveillance and Response System. The recommendations issued are used by the national vaccine regulatory agencies and pharmaceutical companies to develop, produce, and license influenza vaccines for the following influenza season.
The periodic update of viruses contained in influenza vaccines is necessary for the vaccines to be effective due to the constant evolving nature of influenza viruses, including those circulating and infecting humans.
The WHO recommends that quadrivalent vaccines for use in the 2022-2023 influenza season in the northern hemisphere contain the following:
Egg-based vaccines
- an A/Victoria/2570/2019 (H1N1)pdm09-like virus;
- an A/Darwin/9/2021 (H3N2)-like virus;
- a B/Austria/1359417/2021 (B/Victoria lineage)-like virus; and
- a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
Cell culture- or recombinant-based vaccines
- an A/Wisconsin/588/2019 (H1N1)pdm09-like virus;
- an A/Darwin/6/2021 (H3N2)-like virus;
- a B/Austria/1359417/2021 (B/Victoria lineage)-like virus; and
- a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
The WHO recommends that trivalent vaccines for use in the 2022-2023 influenza season in the northern hemisphere contain the following:
Egg-based vaccines
- an A/Victoria/2570/2019 (H1N1)pdm09-like virus;
- an A/Darwin/9/2021 (H3N2)-like virus; and
- a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
Cell culture- or recombinant-based vaccines
- an A/Wisconsin/588/2019 (H1N1)pdm09-like virus;
- an A/Darwin/6/2021 (H3N2)-like virus; and
- a B/Austria/1359417/2021 (B/Victoria lineage)-like virus
The full 11-page PDF document describing their rationale can be read at:
As always, we probably won't know how effective this vaccine formulation will be against next fall's flu season until early 2023. But even if it isn't a perfect match, a little protection beats none at all.
