Public Health Watch: Second Thoughts on a Second Booster?

To boost (again), or not to boost. That is the question (with apologies to Shakespeare).

In recent weeks, the US Food and Drug Administration expanded its authorization of the Pfizer/BioNTech and Moderna COVID-19 vaccines to include a second booster dose for adults age 50 years and older, provided it has been at least 4 months since their last booster. However, while the additional shot is available—and recommended by the US Centers for Disease Control and Prevention (CDC)—Americans appear to be in no rush to receive it.

Of the 218.1 million people across the country who are “fully vaccinated”—meaning they have received the 2 original doses of an mRNA vaccine—well under 50%, or 98.4 million, have gotten a booster, based on CDC figures through April 7th. At least part of this relatively low demand may be the result of “vaccine fatigue” among some of the public, according to media reports.

However, there is also data suggesting that a fourth dose of either of the vaccines provides “marginal benefits” for those with healthy immune systems. Indeed, in an analysis published on April 7th in the New England Journal of Medicine, following receipt of a fourth dose, vaccine efficacy against any SARS-CoV-2 infection during the Omicron wave was 30% for BNT162b2 and 11% for mRNA-1273, or well under the figures seen against earlier variants among the fully vaccinated.

Of course, the vast majority of those infected following receipt of their fourth dose experienced only mild COVID-19 symptoms.

“The efficacy of a fourth dose has to be demonstrated on potential new variants,” Florence Abravanel PharmD, PhD, a virologist with the Institute for Inflammatory and Infectious Diseases at the University of Toulouse in France, told Contagion. Conversely, “we know that 3 doses of vaccine do not prevent infection but prevent the evolution to a severe disease with the Omicron variant.”

Abravanel’s research has focused specifically on the efficacy of booster doses of the COVID-19 in patients who have undergone solid organ transplants and, thus, are immunosuppressed.

Still, while serious adverse events are rare with both mRNA vaccines, recipients can expect to experience headache, fever, and, of course, a sore arm following receipt of a booster dose, or the same symptoms seen after earlier shots. For some at least, being incapacitated for a day with these symptoms—perhaps for a fourth time—appears to be too much to bear.

“Patients that may benefit from a fourth dose include the elderly, those on dialysis, and those with autoimmune systemic diseases,” Abravanel said.

How many of them—and others—will take it up remains to be seen.