Flu Forecasts
Predicting flu season this early is hard, said Jeffrey Shaman, PhD, a professor of environmental health sciences and professor of climate at Colombia University, New York.
“You can look at the CDC forecast and use it as a very loose guide right now,” said Dr. Shaman, who won the CDC’s first “Predict the Influenza Season Challenge” in 2014. “Until there is actually flu, it’s like trying to predict the landfall of a hurricane.” Flu activity remained low as of September 14 (the most current data available), according to the CDC.
When flu activity picks up, typically in mid-October or November, experts look at the dominant strain, exposure to similar strains in previous years, and how well-matched the current flu vaccine is to that dominant strain, Dr. Shaman said. Vaccine makers must make an educated guess months in advance regarding which strain to target, to allow time for production.
The vaccination rate plays a role, too, but that tends to remain constant, Dr. Shaman said. According to the CDC, less than half of adults age 18 and up got a flu vaccination last year.
Experts also consider flu patterns in the Southern Hemisphere, where 2024 flu activity has mostly involved two subtypes of influenza A — H1N1 and H3N2 — and some influenza B, the CDC found.
How Well Do This Year’s Vaccines and Viruses Match Up?
The FDA has authorized three updated COVID vaccines for this fall. Novavax targets the JN.1 strain of SARS-CoV-2, the virus that causes COVID-19. Both mRNA vaccines, Moderna and Pfizer, target KP.2, a descendant of JN.1. All three target current predominant variants, and any one of them is recommended by the CDC.
The vaccines are a good “though not perfect match to virtually all the circulating variants of SARS-CoV-2,” said Dr. Pekosz.
Experts said that the shots will protect against the XEC variant.
“XEC and its sublineages are expected to be the dominant fall/winter variant group,” said Dr. Rajnarayanan.
This year’s flu vaccines, all trivalent (protecting against three viruses), will target the three strains expected to circulate — H1N1, H3N2, and influenza B (Victoria), according to the CDC.
People should still get vaccinated, Dr. Adalja said, and use home tests for flu and COVID and take antivirals promptly when needed. The goal should not be status quo but rather fewer COVID and flu hospitalizations and deaths.
A version of this article first appeared on WebMD.com.