The World Health Organization has already announced the strains of influenza for the 2019-2020 flu season and has made vaccination composition recommendations accordingly. Manufacturers of the vaccine will now operate quickly to produce, test, release and distribute the flu vaccine ahead of the upcoming flu season. The Centers for Disease Control and Prevention (CDC), together with other federal partners, monitor this production process and then vaccine availability timelines, to ensure that virus prevention is available.
How do these agencies know so far ahead of time which flu vaccine will be effective against next year’s virus?
The CDC has reported that the 2018-2019 influenza vaccination had a 47% efficacy rate, making it one of the most effective vaccinations against the flu to date. Data from clinical studies on vaccine effectiveness is taken into consideration when formulating the next season’s vaccination. The vaccine for the 2019-2020 flu season has therefore been updated to better match circulating viruses, however, the flu strain selections are not based solely on the previous year’s strain.
There are more than 100 centers that monitor flu activity year round, in over 100 countries, to help determine what strains of flu are circulating. Thousands of flu virus samples are received and tested, from which representative virus samples are sent to five WHO collaboration centers located around the globe. The information found in these samples, together with laboratory data and genetic characterization, is used to make recommendations on flu vaccine composition for the coming season.
The laboratory data that is used in identifying upcoming strains is taken from immune responses to specific molecular structures identified on the representative samples, noted above. The genetic characterization refers to the mapping of genetic codes that make up each flu strain, from which experts monitor changes in circulating viruses.
Interestingly, the WHO meets twice a year to recommend flu strains for different parts of the world: they meet in February to determine the formula for the Northern Hemisphere’s seasonal flu vaccine (as was published last month) and again in September for the Southern Hemisphere. Each country within those hemispheres then take the WHO’s recommendations and independently determine which strains to include in the upcoming flu vaccine. In the United States, it is the U.S. Food and Drug Administration (FDA) who vote on the final selection of flu strains, based on all available data and recommendations. The FDA plays a critical role in the development and quality control of the seasonal flu vaccine for the United States.
There are several facets of flu prevention that need to be coordinated ahead of the coming flu season. For example, the American Academy of Pediatrics is approving the use of nasal spray-based vaccinations for children who have a hard time receiving the flu shot. The nasal spray has not been recommended for the past two flu seasons, as it was not as effective as the shot against one strain of the virus. But research has shown that for the coming 2019-2020 season, it will once again be an effective replacement for the needle in children.
Another development for the 2019-2020 season comes from the European Health Commission, who has approved the marketing license for the first ever cell-based quadrivalent vaccine, which will be made available for the 2019-2020 flu season, for those aged 9 and older. Research is still underway as to whether there are better influenza related outcomes due to cell-based vaccines and so, for now, these will not be made available in North America.
There is hope that one day, a universal flu vaccine will be developed and made available to everyone. The CDC and FDA report that this possibility is still many years away. For now, each country’s recommended flu vaccine is still the most effective way to prevent contracting the influenza virus.