Antigenic and genetic characteristics of zoonotic influenza A viruses and development of candidate vaccine viruses for pandemic preparedness/Caracteristiques genetiques et antigeniques des virus grippaux A zoonotiques et mise au point de virus vaccinaux candidats pour se preparer a une pandemie.

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Date: Mar. 25, 2022
From: Weekly Epidemiological Record(Vol. 97, Issue 12)
Publisher: World Health Organization
Document Type: Article
Length: 4,606 words
Lexile Measure: 1690L

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February 2022

The development of influenza candidate vaccine viruses (CVVs), coordinated by WHO, remains an essential component of the overall global strategy for influenza pandemic preparedness.

Selection and development of CVVs are the first steps towards timely vaccine production and do not imply a recommendation for initiating manufacture. National authorities may consider the use of one or more of these CVVs for pilot lot vaccine production, clinical trials and other pandemic preparedness purposes based on their assessment of public health risk and need.

Zoonotic influenza viruses continue to be identified and evolve both genetically and antigenically, leading to the need for additional CVVs for pandemic preparedness purposes. Changes in the genetic and antigenic characteristics of these viruses relative to existing CVVs and their potential risks to public health justify the need to select and develop new CVVs.

This document summarizes the genetic and antigenic characteristics of recent zoonotic influenza viruses and related viruses circulating in animals1 that are relevant to CVV updates. Institutions interested in receiving these CVVs should contact WHO at gisrs-whohq@who. int or the institutions listed in announcements published on the WHO website. (2)

Influenza A(H5)

Since their emergence in 1997, highly pathogenic avian influenza (HPAI) A(H5) viruses of the A/goose/Guangdong/1/96 haemagglutinin (HA) lineage have become enzootic in some countries, have infected wild birds and continue to cause outbreaks in poultry and sporadic human infections across a wide geographic area. These viruses have diversified genetically and antigenically, leading to the need for multiple CVVs. Detected viruses with H5 HA gene segments have been paired with a variety of neuraminidase (NA) subtypes (N1, N2, N3, N4, N5, N6, N8 or N9). This summary provides updates on the characterization of A/goose/Guangdong/1/96-lineage A(H5) viruses and the status of the development of influenza A(H5) CVVs.

Influenza A(H5) activity from 24 September 2021 through 23 February 2022

Twenty-six human infections with A/goose/ Guangdong/1/96-lineage viruses were reported in this period. Since 2003, there have been 3 A(H5), 7 A(H5N8), 74 A(H5N6) and 864 A(H5N1) human infections reported. Since September 2021, A/goose/ Guangdong/1/96-lineage A(H5) viruses have been detected in both domestic and wild birds in many countries, and also in wild mammals in Europe (Table 1).

The nomenclature for phylogenetic relationships among the HA genes of A/goose/Guangdong/1/96-lineage A(H5) viruses is defined in consultation with representatives of WHO, the Food and Agriculture Organization of the United Nations (FAO), the World Organisation for Animal Health (OIE) and academic institutions. (3)

Antigenic and genetic characteristics of influenza A(H5) viruses

Twenty-five of the human infections were identified in China and one in the United Kingdom of Great Britain and Northern Ireland (United Kingdom). The human infections in China were caused by A(H5N6) viruses and sequence data generated from 16 of the cases identified A(H5) clade viruses. The HAs of these viruses were similar to A/Astrakhan/3212/2020 (1 to 4 amino acid differences), from which a clade CVV has been developed. A post infection ferret antiserum raised against the A/Astrakhan/3212/2020 CVV reacted well to most, but not all, of...

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