A single injection of the Pfizer / BioNTech or Moderna covid-19 vaccine could be enough to provide immunity to people already infected with the coronavirus, according to work published in the New England Journal of Medicine.
Those responsible are researchers at the Icahn School of Medicine at Mount Sinai, New York, who point out that the efficacy of a single dose “would help increase the limited vaccine supply.
In addition, this change could also prevent unnecessary side effects from a second dose of the vaccine, which the researchers say are “significantly greater in people with pre-existing immunity to SARS-CoV-2, the virus that covid-19.”
“We show that the response of antibodies to the first dose of the vaccine in people with pre-existing immunity is equal to or even greater than the response in uninfected people after the second dose,” said Viviana Simon, author of the study. article.
Therefore, he adds, “we believe that a single dose of the vaccine is sufficient for people already infected with SARS-CoV-2 to achieve immunity.”
In a statement from Mount Sinai Hospital, the researchers recalled that the vaccines Pfizer-BioNTech and Moderna received FDA approval for emergency use by the US regulatory agency in December 2020.
In phase III studies, both reported high efficacy in preventing symptomatic COVID-19 infections after two doses administered three to four weeks apart. Both are also well tolerated, with few side effects requiring additional medical attention.
Now, in the study of 109 subjects with and without prior immunity to SARS-CoV-2, the researchers found that the first group developed antibodies within days of the first dose at a rate 10 to 20 times higher than those who took that did not. She had passed the disease at a rate of more than ten times after the second puncture.
“These results suggest that a single dose of the vaccine elicits a very rapid immune response in subjects who have tested positive,” said Florian Krammer, adding that the first dose is immunologically comparable to the booster (second) in people who have not been . infected.
The team also examined responses after the first dose of the vaccine in a second group of 231 subjects, 83 of whom tested positive for COVID-19 and 148 who had not.
Although the vaccines were generally well tolerated, injection site symptoms such as pain, swelling and redness of the skin were observed in both subgroups.
However, adverse reactions were significantly more common in recipients with pre-existing immunity, including fatigue, headache, chills, fever, and muscle or joint pain.
Viviana Simon suggests that if a person’s history of infection is unknown, using a serological test to look for antibodies: “If the screening process determines their presence as a result of a previous infection, then a second injection of the vaccine may not be necessary. “concludes.