Published 02 September 2021
New studies by Pitt Graduate School of Public Health researchers suggest a sharp rise in influenza cases this with, potentially a half-million more flu hospitalizations that usual. Last year's flu season was one of the mildest on record leading to waning population-level immunity, as fewer people developed a natural immunity from influenza.
“As covid-19 mitigation measures — such as masking, distancing and school closures — are relaxed around the world, we’re seeing a fierce resurgence of other respiratory viruses, which does not bode well for the coming flu season,” said Dr. Mark Roberts, Public Health Dynamics Laboratory director and senior author of both studies. “In a worst-case situation with a highly transmissible flu strain dominating and low influenza vaccination uptake, our predictive models indicate the potential for up to nearly half a million more flu hospitalizations this winter, compared to a normal flu season.”
Using PHDL's Framework for Reconstructing Epidemiologic Dynamics (FRED), PHDL research professor Mary Krauland led a team whose research indicated that the 2021-22 flu season could have 20% more influenza cases than a normal year - with the potential for the flu caseloads to double. This study, Agent-based Investigation of the Impact of Low Rates of Influenza on Next Season Influenza Infections, is currently in preprint.
Pitt Public Health postdoctoral researcher Kyueun Lee led a team using the Susceptible-Exposed-Infected-Recovered model to determine that a 75% flu vaccination rate would substantially limit additional hospitalizations. This models suggests that 600,000 hospitalizations are possible during the 2021-22 flu season, 100,000 more than normal. This study, Predicting the impact of low influenza activity in 2020 on population immunity and future influenza season in the United States, is in preprint.
“My own personal feeling is that we probably are going to be OK here in Western Pennsylvania,” Roberts said, noting that both UPMC and Allegheny Health Network “have all of the modern treatment facilities and have been doing this for a long time” without being “stretched to the breaking point.”
Covid-19 precautions persisting could possibly result in another mild flu season, resulting in natural immunity waning even farther with an even higher possibility of a more-severe flu season when social activities return to normal.
“This is not to suggest that we should stop covid-19 mitigation efforts to avoid a severe flu season,” said Roberts, who is a professor of health policy and management at Pitt Public Health. “Instead, it shows that more of us — particularly young children — will be susceptible to the flu and that vaccination is absolutely essential to avoiding bad outcomes.”