Researchers from Bar-Ilan University and Ziv Medical Center have presented preliminary evidence that people previously infected with coronavirus responded positively and strongly to one dose of the Pfizer vaccine, regardless of when they were infected and whether or not they had detectable antibodies prior to being inoculated.
The study was conducted on a group of 514 staff members at Ziv Medical Center in Safed, 17 of whom were infected with COVID-19 between one and 10 months before receiving the first dose of the vaccine.
Antibody levels of the group were measured before and after receiving the shot in order to determine the 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 in certain situations.
“This finding can help countries make informed decisions regarding vaccine policy – for instance, whether those previously infected should be vaccinated in priority and, if so, with how many doses,” says Prof. Michael Edelstein of Bar-Ilan University's Faculty of Medicine, who led the study.
“It also offers reassurance that not having detectable antibodies after being infected does not necessarily mean that post-infection protection is lost,” he says.
However, the researchers emphasized that their findings should be confirmed in a larger cohort before reaching definitive conclusions.
The researchers are continuing to track healthcare workers after their second dose to better understand how long the vaccine will protect against COVID-19 in different groups of people.
France on Friday recommended that people who have already recovered from Covid-19 receive a single vaccine dose, becoming the first country to issue such guidance.