Flu activity has been virtually nonexistent during the COVID-19 pandemic, but that could change soon: Two new studies predict that the flu will come roaring back this fall and winter.
The findings, posted this week to the preprint database medrXiv and not yet peer-reviewed, underscore the importance of flu shots this year — both studies suggested that a bad flu season could be avoided if flu vaccination rates increased by 20% to 50% compared with a typical year. "Vaccinating as many people against flu as possible will be key to avoiding this scenario," Dr. Mark Roberts, director of the Public Health Dynamics Laboratory at the University of Pittsburgh Graduate School of Public Health, and senior author of both studies, said in a statement.
Last year had historically low levels of flu activity, likely due to measures for preventing COVID-19, such as social distancing, school closures, mask wearing and reduced travel. During the 2020-2021 flu season, the overall flu hospitalization rate in the U.S. was only about 4 hospitalizations per 100,000 people; compared with the usual rate of 70 hospitalizations per 100,000 people. Flu-related deaths dropped by 95%, the researchers said.
This means that the U.S. population "missed the opportunity to establish or boost their immunity [to the flu] for the future influenza season," which raises the concern that the flu could make a comeback when preventive measures for COVID-19 are lifted, the researchers said. They note that the U.S. is already seeing a rise in cases of other respiratory infections, such as respiratory syncytial virus (RSV), "which does not bode well for the coming flu season," Roberts said.
The second study, led by Mary Krauland, who studies mathematical modeling at Pitt Public Health, used a different model, called the Framework for Reconstructing Epidemiologic Dynamics, to simulate flu cases and hospitalizations over two sequential flu seasons, and found similar results. The findings suggested that the 2021-2022 flu season could see a 20% increase in flu cases compared with a typical season. Young children (younger than age two) would be particularly at risk for flu in the 2021-2022 season because they are unlikely to have any previous exposure to the disease, the authors said.
But increasing flu vaccination rates by just 10% could reduce hospitalizations by 6% to 46%, depending on the transmissibility of the flu this season, the study found.
"The 'twindemic' — a coinciding flu and COVID-19 epidemic — overwhelming our hospitals was thankfully avoided last year. But that does not mean it is no longer possible," Roberts said. "If anything, our models show that we should be more concerned this year about the possibility of a surge in COVID-19 hitting at the same time as a massive flu outbreak in areas of the country with low vaccination rates against both diseases."
Originally published on Live Science.
