Do We Really Need a Yearly COVID Vaccine?

On June 15th, an FDA Vaccine Advisory Committee picked the strain for “this year’s” vaccine.

During the past 3 years, the FDA has recommended three different compositions for COVID vaccines. The most recent change was made last week.

Three years ago, in December 2020, the FDA Vaccine Advisory Committee recommended authorization of COVID mRNA vaccines made by Pfizer and Moderna. Both vaccines were designed to prevent one strain—the Wuhan-1 or ancestral strain. These vaccines were used throughout 2021 and most of 2022. On June 28, 2022, the FDA Committee recommended authorization of a two-in-one (bivalent) vaccine that contained both the original ancestral strain plus one of the omicron variants (BA.4/BA.5). In September 2022, the CDC recommended this bivalent vaccine as a booster dose for everyone over 6 months of age. Last week, on June 14, 2023, the Committee recommended a vaccine that contained only one of the omicron variants (XBB.1.5).

Do we really need a yearly COVID vaccine? Is COVID like flu?

Every year, the CDC recommends an influenza vaccine for anyone over 6 months of age. That’s because influenza virus changes so much from one year to the next that natural infection or immunization the previous year doesn’t protect against severe disease. Like COVID vaccines, the goal of influenza vaccines is to keep people out of the hospital, out of the intensive care unit, and out of the morgue. To determine which strains to include in the yearly influenza vaccines, members of the FDA Vaccine Advisory Committee gather in the first week of March to listen to presentations by the Department of Defense, the World Health Organization, the FDA, and the CDC. If the FDA Advisory Committee incorrectly predicts which strains to include in the annual influenza vaccine, which happened twice in the past ten years, the results can be disastrous; a miss is a mile. Vaccine efficacy against severe influenza when the strains in the vaccine don’t match the circulating strains was less than 15 percent. In other words, protection against severe influenza is strain specific.

Is SARS-CoV-2 virus similar enough to influenza virus to require a yearly vaccine? Asked another way, does SARS-CoV-2 virus change so much from one year to the next that people who were previously vaccinated or naturally infected or both are no longer protected against severe illness? Is protection against severe COVID, like influenza, also strain-specific? As of now, the answer to these questions is “No.” Healthy young people who have been vaccinated against SARS-CoV-2 remain protected against severe disease the following year because, although new variants continue to evolve, the parts of the virus that are recognized by T cells have remained relatively unchanged. And T cells are critical in protecting against severe COVID. Unlike influenza, protection against severe COVID has not, thus far, been strain specific.

For now, yearly booster dosing is probably best reserved for groups that are at highest risk of severe disease, such as people with multiple comorbidities, people over 75, people who are immune compromised, and people who are pregnant.