During the COVID-19 pandemic, the number of influenza cases fell to historic lows. Experts attribute this phenomenon to wearing masks and other precautions to combat the new type of coronavirus.
Two types of influenza viruses have not been detected in anyone for a year around the world. Experts do not yet know if they are extinct, but if they are, it will be easier for doctors to select strains of influenza viruses for the seasonal vaccine.
Seasonal influenza is caused by two families of influenza viruses: influenza A and influenza B. Influenza A viruses are classified into “subtypes” based on two proteins on their surface known as hemagglutinin (H) and neuraminidase (N). According to the Centers for Disease Control and Prevention (CDC), H1N1 and H3N2 are currently circulating in humans, and each of these subtypes is subdivided into subtypes.
Influenza B viruses, on the other hand, are not subtyped but fall into two lineages known as B/Yamagata and B/Victoria.
One subtype of H3N2, known as 3c3.A, has not been detected since March 2020. According to the STAT, the same can be said for the B / Yamagata lineage.
Every year, scientists make a flu vaccine months before the actual start of the virus season, observing which strains are circulating around the world and then predicting which ones are likely to spread in the coming season. The reduced variety of influenza subtypes will result in the strains in the vaccine being matched to those in circulation.