The World Health Organization (WHO) has announced the recommended viral composition of influenza vaccines for the 2023 southern hemisphere influenza season, which will be used by national vaccine regulatory agencies and pharmaceutical companies to develop, produce, and licence influenza vaccines for the following season.
The recommendation is based on the advice of a group of experts from WHO Collaborating Centres (CC) and WHO Essential Regulatory Laboratories that analyse virus surveillance data generated by the WHO Global Influenza Surveillance and Response System, a global network of over 150 laboratories in 127 countries, areas or territories set up in 1952.
WHO cites influenza vaccination as the current principal means of reducing or counteracting influenza mortality and morbidity burden, but the constantly evolving nature of influenza viruses requires continuous global monitoring and frequent reformulation of influenza vaccines.
‘Around a billion people get seasonal influenza every year and the threat of an influenza pandemic is ever-present. For this reason, the need to monitor circulating respiratory viruses, including influenza, continues to be critical. This monitoring informs the vaccine composition recommendations that WHO issues twice a year,’ WHO said in a statement.
The egg-based quadrivalent vaccines recommended by WHO for use in the 2023 southern hemisphere influenza season contain an A/Sydney/5/2021 (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.
The cell culture- or recombinant-based quadrivalent vaccines contain an A/Sydney/5/2021 (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.
WHO’s recommendations for egg-based trivalent vaccines contain an A/Sydney/5/2021 (H1N1)pdm09-like virus; an A/Darwin/9/2021 (H3N2)-like virus; and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
Finally, the cell culture- or recombinant-based trivalent vaccines contain an A/Sydney/5/2021 (H1N1)pdm09-like virus; an A/Darwin/6/2021 (H3N2)-like virus; and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
Once developed, the candidate reassortants are sent to WHO CCs for characterisation of their antigenic and genetic properties before being released to interested institutions on request.
Reference reagents are then developed and standardised by Essential Regulatory Laboratories, in collaboration with vaccine manufacturers and subsequently made available to manufacturers worldwide upon request, WHO outlined.