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WHO EMRO Weekly Epidemiological Monitor: Volume 12, Issue 41 (13 October 2019)

Situation Report
Originally published
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Current major event

Recommended composition of influenza virus vaccines for use in the 2020 Southern Hemisphere influenza season

The World Health Organization (WHO) announced the composition of influenza virus vaccines for use in the 2020 Southern Hemisphere influenza season on 27 September 2019. Two strains of vaccine virus have changed since the recommendation for the Northern Hemisphere vaccine for the 2019/20 winter.

Editorial note

Each year, WHO convenes experts consultation meeting in February and September annually to set recommendations on the composition of the influenza vaccines in the northern and southern hemispheres seasons respectively. The periodic review and replacement of viruses contained in influenza vaccines is necessary in order for the vaccines to be effective due to the constant evolving nature of influenza viruses, including those circulating and infecting humans. The consultations involve the representatives from five major WHO collaborating influenza centres, three major regulatory authorities, OIE/FAO Network of expertise on animal influenza (OFFLU) and other experts, to review all of the available information on influenza, epidemiological, antigenic and genetic at that time and to recommend the most appropriate formulation for the coming season’s vaccine. The experts also review the latest information on zoonotic influenza viruses and recommend new candidate vaccine viruses for pandemic preparedness, if needed.

Between February and September 2019, influenza activity was reported globally, with influenza A (H1N1) pdm09, A (H3N2) and both lineages of influenza B viruses co-circulating. Influenza A viruses predominated in most countries, with co-circulation of 2009 H1N1 and H3N2 seen in all countries. Influenza B, circulated in higher proportions in Southeast Asia and in some countries in the South America. The Victoria lineage was predominant in most of the regions, except South America, which saw more Yamagata lineage viruses.

The WHO recommendations are made with a knowledge of the currently circulating viruses globally. WHO recommended two changes, compared to the last trivalent and quadrivalent vaccines for the 2018–2019 season in the northern hemisphere influenza season. The new H3N2 component is A/South Australia/34/2019 which replaced A/ Kansas/14/2017, the new influenza B Victoria lineage strain is B/ Washington/02/2019, which replaced B/ Colorado/06/2017, the one the experts recommended for last season's Northern Hemisphere vaccines and last season's Southern Hemisphere vaccine. The advisory group's kept the 2009 H1N1 strain, the same as the last season Northern Hemisphere vaccine.

While all the countries in the Eastern Mediterranean Region (EMR) are in the northern hemisphere, but they don’t all have same temperate zone influenza transmission, and some of the countries in EMR have transmission throughout the year, therefore some use both composition of vaccines.