People who have already had COVID-19 — even if they didn’t show symptoms — may be able to get away with just a single dose of a two-dose coronavirus vaccine, a study of health care workers suggests.

Researchers tested for antibodies in the blood of 59 health care workers who got vaccinated with either the Pfizer or Moderna vaccines. Some of the volunteers had COVID-19 eight to nine months before vaccination.

“Their bodies remembered it, no problem,” and reacted very quickly to the vaccine, says Mohammad Sajadi, an infectious disease doctor at the Institute of Human Virology at the University of Maryland School of Medicine in Baltimore. After the first vaccine dose, antibody levels quickly shot up in people who previously had COVID-19 either with or without symptoms to more than 500 times the levels seen in people who were never infected.

Those results, published March 1 in JAMA, suggest that people who have had COVID-19 could get one shot or be moved to the end of the line for vaccinations. An estimated 9 percent of people in the United States have had confirmed cases of COVID-19. Limiting those people to one dose of vaccine could free up 4 to 5 percent of vaccine doses, Sajadi says. 

“Immunologically it makes sense,” he says. “With the ongoing pandemic and vaccine shortages, it makes sense, too. The cost of inaction is just too great” not to spare vaccine doses where possible.