Covid-19 survivors who received the first dose of the Covid-19 vaccine are generating immune responses that could make a second injection unnecessary, potentially freeing up the limited vaccine supply for more people, suggest several new research papers.
The research, although preliminary, found that previously infected people generated protection against the disease quickly and at dramatically higher levels after a first injection of the current two-dose regimens, compared to people who were vaccinated but did not become ill.
“Everyone should be vaccinated. Not everyone needs two injections, ”said Viviana Simon, professor of microbiology at the New York Icahn School of Medicine on Mount Sinai and author of a study. “As long as we can’t deliver that much vaccine to everyone who wants it, I think it’s an important consideration.”
The research, which was posted on prepress servers but not peer-reviewed or published in a scientific journal, comes at a time when other findings of the two-dose regimen for healthy members of the general population highlight the immunological benefits after the first injection. On Friday, researchers in Israel reported that a single injection of the vaccine from Pfizer Inc. and BioNTech SE is 85% effective in preventing symptomatic diseases 15 to 28 days after administration.
Clinical trials of Pfizer and BioNTech’s two-dose vaccines, as well as Moderna Inc., showed that their vaccines are safe and highly protective against Covid-19 when administered in two doses over several weeks. However, the Pfizer study excluded individuals with symptomatic Covid-19, and Moderna excluded people with a previously known infection, leading researchers to see how the immune system in previously sick people responded.