The Covid-19 pandemic has led to the extinction of some flu variants due to infection control measures and travel restrictions. However, this paradoxically means that future flu waves will be stronger than before. According to a study published on the preprint server In Review by the University of Hong Kong, the numerous protective measures implemented during the Covid-19 pandemic in 2020 and 2021 have resulted in a near-complete absence of seasonal flu waves. The study found that this has caused some known lines of the influenza virus to disappear, including virus lines that are included in the current flu vaccine.
The team led by Vijaykrishna Dhanasekaran analyzed data from the Global Influenza Surveillance and Response System (GISRS) of the World Health Organization (WHO), which provides a comprehensive overview of global surveillance and sequence data. According to GISRS data, the Yamagata line of influenza B, which is also included in the current flu vaccine for the 2021/22 season, is very likely to have become extinct since April 2020. The extinction of flu variants is due to the global travel restrictions and infection control measures of the Covid-19 pandemic, which not only prevent the spread of SARS-CoV-2 but also prevent regional outbreaks of influenza B from spreading.
Experts agree that the absence of seasonal flu will lead to significantly more severe waves if Covid-19 measures are lifted. This is because immunity to the virus decreases over time, and the current situation leads to a highly variable distribution of virus lines in different regions of the world. In some regions, rare virus lines will appear during the next flu wave that are not covered by existing vaccines and against which the population has little protection from previous infections.
