WHO Updates 2019-2020 Influenza Vaccine Recommendations for Northern Hemisphere

The World Health Organization (WHO) has announced that a new influenza A(H3N2) component is recommended for the 2019-2020 seasonal flu vaccine. The decision comes following a delay in the decision to replace the component that was included in the vaccine for the 2018-2019 flu season.

Each year, WHO convenes technical consultations in February and September to set recommendations for influenza vaccines for flu seasons in the northern and southern hemispheres. At the WHO consultation on February 19-21, 2019, experts reviewed surveillance data on seasonal influenza activity collected from September 2018 to January 2019. “The majority of A(H3N2) viruses collected from September 2018 to January 2019 belonged to the phylogenetic subclade 3C.2a1b; however, the number of clade 3C.3a viruses has increased substantially since November 2018 in several geographic regions,” the experts noted in the February report. “There has continued to be considerable genetic diversification of the HA and NA genes.”

Due to recent changes in the proportions of genetically and antigenically diverse A(H3N2) viruses, in February the members of the WHO Global Influenza Surveillance and Response System postponed the recommendation of the A(H3N2) component. On March 21, 2019, the WHO released an addendum to the February report with a decision to recommend a A/Kansas/14/2017 (H3N2)-like virus for use in flu vaccines for use in the northern hemisphere’s 2019-2020 flu season. The new component replaces an A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus in use in the northern hemisphere flu vaccine for 2018-2019 flu season.

In an interview with Contagion^®, WHO spokesperson Christian Lindmeier explained the delay and the ultimate decision. “Influenza A(H3N2) viruses have presented an increasing challenge for vaccine virus selection due to frequent changes in the virus and difficulties in generating candidate vaccine viruses for use in egg-based manufacturing,” said Lindmeier, noting that experts reviewed data on virus surveillance, antigenic characterization, and virus fitness forecasts, and identified multiple co-circulating influenza A(H3N2) virus groups before making the recommendation. “In recent months, the proportion of viruses in one antigenically distinct group has increased in many countries, prompting a delay in the selection of the A(H3N2) vaccine component. This delay allowed more time for monitoring virus circulation and characterization of appropriate vaccine viruses.”

Earlier in March, the WHO announced the release of a new global influenza strategy for 2019-2030 to prevent seasonal flu and prepare for the next flu pandemic. “Although it is impossible to predict when the next pandemic might occur, its occurrence is considered inevitable, and it could well occur during the time frame of this strategy,” the new report reads, noting that there are an estimated 1 billion cases of flu worldwide each year, resulting in 290,000 to 650,000 flu-related respiratory deaths. “Given increased economic globalization, urbanization and mobility, the next pandemic will spread further and faster, and could lead to significant disruptions.”

The new strategy aims to build and leverage stronger disease surveillance in more countries and develop better tools to prevent, detect, control and treat flu. “With the partnerships and country-specific work we have been doing over the years, the world is better prepared than ever before for the next big outbreak, but we are still not prepared enough,” said WHO Director-General Tedros Adhanom Ghebreyesus, MSc, PhD, in a recent statement. “This strategy aims to get us to that point. Fundamentally, it is about preparing health systems to manage shocks, and this only happens when health systems are strong and healthy themselves.”