This week, the United States reached a grim milestone: more than 500,000 people have died from COVID-19, while since the beginning of the pandemic an estimated 28.2 million Americans have been infected with the novel coronavirus. As the vaccine roll-out continues, scientists are working to better understand COVID-19 survivors' immune responses as they gauge how many doses of the COVID-19 vaccine are needed.
Intriguingly, multiple studies now suggest that merely one shot of a two-shot vaccine regimen might suffice to protect the tens of millions of Americans who have already recovered from COVID-19.
According to one study posted on the preprint server medRxiv, which has yet to be peer-reviewed, one shot of either the two-shot Pfizer-BioNTech or Moderna vaccines significantly increased the amount of T-cells and antibodies in the blood samples of COVID-19 survivors. Notably, one shot of either vaccine also neutralized the B.1.351 variant in the same group's blood samples. The B.1.351 variant emerged in South Africa and is believed to be more transmissible. Previous studies have found that the Pfizer-BioNTech and Moderna vaccines in people who haven't had COVID-19 are less effective against the variant.
The study adds to previous ones with similar results. Researchers at New York University found that a second dose of the Pfizer-BioNTech vaccine in COVID-19 survivors didn't add much benefit, either. A third study reached a similar conclusion.
Currently, the Centers for Disease Control and Prevention (CDC) states that after patients have recovered from COVID-19, they should be vaccinated as usual — with no caveat about only needed one dose of the two-shot vaccines.
"That's because experts do not yet know how long you are protected from getting sick again after recovering from COVID-19," the CDC states on its website. "Even if you have already recovered from COVID-19, it is possible—although rare—that you could be infected with the virus that causes COVID-19 again."
However, the CDC adds that if a person were treated for COVID-19 with monoclonal antibodies or convalescent plasma, that person should wait 90 days before getting a COVID-19 vaccine. Notably, giving one dose of the vaccine to COVID-19 survivors could potentially speed up the vaccination process because extra doses could be redistributed by health officials.
"I think one vaccination should be sufficient," Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai, previously told The New York Times. "This would also spare individuals from unnecessary pain when getting the second dose and it would free up additional vaccine doses."
The country's initial limited supply has contributed to the slow roll-out. Vaccinating as many people as soon as possible is critical as the coronavirus mutates and more contagious variants emerge.
"We need as many people as quickly as possible, and this is one of the ways to go about doing that," said Buddy Creech, director of the Vanderbilt Vaccine Research Program in Nashville, Tenn., told the Wall Street Journal. "If we had a significant portion of the population that could get only one vaccine and be done, that really allows us to move even more quickly."
Beyond COVID-19 survivors, separate studies are also indicating that one shot of the two-shot vaccines are effective in people who haven't had COVID-19, too.