THIS year’s flu vaccine isn’t a perfect match against the dominant influenza strain circulating at the moment.
Although this season’s shot contains a version of H3N2, the H3N2 strain circulating has picked up new mutations, leading to a slight vaccine mismatch.
Experts, however, say that even an imperfect flu shot can provide strong protection against illness and, more importantly, hospitalization and death.
This year’s flu vaccine isn’t a great match against the dominant influenza strain circulating right now, according to a recent preprint study.
While this might sound alarming, experts say it’s actually unusual for there to be a perfect match between the flu shot and the circulating strains.
One of the strains included in this year’s shot — H3N2 — has picked up multiple mutations, leading to a vaccine mismatch. The slight mismatch identified in the study doesn’t mean that the shot is no longer effective, according to experts.
In fact, the flu shot will still be able to prevent many illnesses and keep many more who get sick with the flu out of the hospital, says Dr. William Schaffner, an infectious diseases specialist at Vanderbilt University in Nashville, Tennessee, and the medical director of the National Foundation for Infectious Diseases.
“Even if you get flu with that strain, you’re very likely to have a less severe infection,” Schaffner told Healthline.
According to Dr. Marie-Louise Landry, the director of the Clinical Virology Laboratory and professor of laboratory medicine and medicine (infectious diseases) at Yale School of Medicine in New Haven, Connecticut, the influenza vaccine contains four different influenza strains: two A and two B. The circulating H3N2 strain has multiplied millions of times and in that process mutated to be slightly off target from the vaccine.
Even though the version of H3N2 that’s included in this year’s shot is an imperfect match to the H3N2 strain going around, there’s still substantial overlap between the strains for the shot to provide meaningful protection, according to Schaffner.
The drift may mean that shot may be slightly less effective at preventing infections, but it should still help lessen the severity of disease, Landry told Healthline.In addition, the shot may still do a good job of targeting other A and B strains that are circulating.
“Even if there is a mismatch for one, the vaccine can prevent infection with the other three, and there may be milder disease with the breakthrough virus,” Landry said.
