Which booster shot is likely to be more effective and long lasting, a full dose of Pfizer or a half-dose of Moderna?

— Bill in Oregon

Now that the Centers for Disease Control and Prevention has said people can get a different company’s vaccine booster from their original dose, your question is almost certainly a common one. The CDC plans to release more information soon about who might benefit from one brand over another.

For now, we know that both Pfizer-BioNTech’s full-dose booster and Moderna’s half-dose booster significantly increase a person’s virus-fighting antibodies. Pfizer announced last week that its booster was 95.6 percent effective at protecting vaccinated people, while Moderna found that its half-dose booster restored waning antibody levels.

Although it may sound counterintuitive, a half-dose booster is not necessarily inferior to a full dose.

That’s because a primary vaccination series — two doses of Pfizer or Moderna, or one dose of Johnson & Johnson — teaches the immune system to recognize and defend against the coronavirus’s spike protein. A booster activates immunological memory, meaning that immune cells essentially remember previously received vaccines. A lower dose is often effective for this purpose.

Studies have not yet been done to determine how long Pfizer’s and Moderna’s boosters offer protection and whether one is more effective than the other. But Lee Harrison, an epidemiologist at the University of Pittsburgh, told The Washington Post that he does not expect to see significant differences between the brands by either measure.

“I would feel extremely confident in the increased protection provided by a booster dose of either of the two mRNA vaccines,” he wrote in an email.

If you’re debating which one to get, we suggest keeping an eye out for the CDC’s upcoming guidance and talking with your doctor about which booster might be best for you.

— Marisa Iata