U.S. health officials are watching two key factors to determine if and when Americans will need COVID-19 vaccine boosters, Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, said during a June 17 White House briefing.
The first factor is vaccine durability, or the length of protection against the virus. This can be determined by looking at the correlates of immunity for a cohort of vaccinated individuals and ensuring these metrics don't go below a critical baseline.
The second factor is how many breakthrough infections are occurring among vaccinated people. A rise in breakthrough infections would suggest decreasing immunity, according to Dr. Fauci.
"We hope we don't get to that point, [that] we'll know about it before," he said.
Clinical trials for COVID-19 vaccine boosters against the "wild type" of the virus and specific variants are ongoing, Dr. Fauci said.
Ultimately, the timeline for a potential booster is still unclear.
"That could be a year. That could be 18 months. That could be much longer," Dr. Fauci said. "We're going to have to follow it. And we will act according to the information that we get from the parameters that I just mentioned."