When We'll Know If This Year's Flu Vaccine Misses The Mark

As of October 28, the U.S. Centers for Disease Control and Prevention (CDC) reported that over 128 million doses of the flu vaccine had been administered across the country for the 2022 season thus far. While last year's flu season proved to be more mild than in years past, we saw an early peak in flu cases this year beginning in April 2022 (via GoodRx Health). As to whether or not this year's flu season will be more severe than that of 2021 remains to be seen. However, those at least 6 months of age are encouraged to receive their yearly flu shot, which has been shown to offer an average protection rate of anywhere from 40% to 60%.

This year, nine different flu vaccines have been authorized for use by the U.S. Food and Drug Administration (FDA), all of which are categorized as quadrivalent vaccines, reports GoodRx Health. Dr. Bernadette Boden-Albala, director and founding dean of the Program in Public Health at the University of California, Irvine, further explains, telling Healthline, "All flu vaccines in the United States are 'quadrivalent' vaccines, which means they protect against four different flu viruses." These strains include the influenza A(H1N1) virus, influenza A(H3N2) virus, and two influenza B viruses. Of the nine vaccines offered for the 2022-2023 season, all are distributed intramuscularly with one being offered in the form of a nasal spray (per GoodRx Health).

Determining the flu vaccine's efficacy

So when exactly will we know if this year's flu vaccines hit the mark in targeting the currently circulating strains? Experts at Healthline report that we will likely know more in the coming months. Various factors will influence this timeline, such as the fact that we have yet to reach the height of flu season. When case numbers increase, health professionals are better able to calculate how the flu shot stacks up against current viral strains.

Additionally, health experts base each year's flu shot formula off of research to predict which strains will likely be most active each season (per Healthline). "The composition of flu vaccines is reviewed annually by the Centers for Disease Control and Prevention (CDC)," Dr. Bernadette Boden-Albala tells Healthline. "Vaccines are updated to protect against the viruses that research indicates will be most common during the upcoming flu season." However, because this research can only offer a calculated prediction, and because flu strains can mutate at a rapid pace, it's possible for the flu vaccine to miss the mark. Therefore, mutations are another factor that may influence how soon we will know about the current flu vaccine's efficacy.