People previously infected with the novel coronavirus responded very strongly to one dose of the Pfizer vaccine, regardless of when they were infected and whether or not they had detectable antibodies against Covid-19 prior to receiving the vaccine, a new study suggests. According to the researchers, the strong response to one dose of the vaccine among those previously infected regardless of the duration between infection and vaccination is good news.
"This finding can help countries make informed decisions regarding vaccine policy -- for instance, whether those previously infected should be vaccinated on priority and, if so, with how many doses," said researcher Michael Edelstein from the Bar-Ilan University.
"It also offers reassurance that not having detectable antibodies after being infected does not necessarily mean that protection following infection is lost," Edelstein added.
For the study, published in the journal Eurosurveillance, the research team included 514 participants. Seventeen of them were infected with Covid-19 anytime between one and ten months before receiving the first dose of the vaccine.
Antibody levels of the entire cohort were measured prior to vaccination and thereafter to determine response to the vaccine.
The response among those previously infected was so effective that it opens the debate as to whether one dose of the vaccine may suffice, the team said.
However, the researchers emphasise that their findings should be confirmed in a larger cohort before reaching definitive conclusions.
The researchers are continuing to follow healthcare workers after their second dose to better understand how long the vaccine will protect against Covid-19 in different groups of people.