The research, involving more than 260 individuals, showed that a single dose of the Pfizer-BioNTech vaccine for individuals who previously had Covid-19, can generate an immunologic response similar to that of individuals receiving the two-dose recommended sequence.

The Pfizer and BioNTech vaccine is normally administered in two doses, 21 days apart, to provide nearly full protection against the novel coronavirus, known as SARS-CoV-2.

Post-vaccine symptoms were more prominent for those with prior infection after the first dose, but it was similar between the two groups after the second dose, the findings, published in the journal Nature Medicine, revealed.

"Our findings extend those from smaller studies reported elsewhere and support a potential strategy of providing a single dose of vaccine to persons with a confirmed prior history of coronavirus infection, along with two doses for people not previously infected," said Susan Cheng, Associate professor at the Cedars-Sinai Medical Centre in California, US.

"This approach could maximise the reach of a limited vaccine supply, allowing potentially millions more people to be vaccinated in the US alone," she added.

However, further study is needed, said the research team. For the study, the team conducted a survey of 1,090 healthcare workers at Cedars-Sinai who had received the Pfizer-BioNTech vaccine. They were asked about prior coronavirus infections and any symptoms they might have experienced after being vaccinated.

The workers also underwent antibody tests to gauge the response of their immune systems to the vaccinations. Antibody levels were measured at three points in time: before or up to three days after the first dose, within seven to 21 days after the first dose, and within seven to 21 days after the second dose.

The team identified 35 individuals with prior coronavirus infections who had received a single vaccine dose and 228 individuals without prior infection who had received both vaccine doses. Based on the antibody tests, the team found that levels and responses of coronavirus-specific antibodies were similar in both of these groups.