A single shot of a Covid-19 vaccine brings greater protection against Covid-19 infection in people who were previously infected with the disease than in those who were not, a U.K. study showed.
The research team in the U.S. conducted the study on healthcare workers who enrolled in the PITCH (Protective Immunity from T-cells to COVID-19 in Healthcare workers) study in four university hospitals (Oxford, Liverpool, Newcastle, and Sheffield), and published the results in the Lancet on Tuesday.
The researchers analyzed 289 healthcare workers vaccinated with Pfizer’s Covid-19 vaccine between Dec. 9, 2020, and Feb. 9, 2021. Of them, 264 received the first dose, and 25 completed the second dose.
Among the first dose recipients, 145 had been infected with Covid-19, and the rest had no history of infection. The 25 people inoculated with the second shot did not have any Covid-19 infection. Healthcare workers who were previously infected received Covid-19 vaccines after a median of 268 days.
On day 28, after the first dose, previously infected healthcare workers had a higher spike-specific T-cell response, measured in peripheral blood mononuclear cells (PBMCs), than those who were infection naïve.
It was notable that the T-cell response in previously infected healthcare workers after a single dose was similar to that of infection-naïve healthcare workers after two doses, the research team said.
Immunoglobulin G (IgG) antibody responses developed after a single dose in previously infected healthcare workers were even higher than infective-naïve healthcare workers who received a single dose or two doses.
“A single dose of the BNT162b2 (Pfizer) vaccine is likely to provide greater protection against SARS-CoV-2 infection in individuals with previous SARS-CoV-2 infection than in SARS-CoV-2-naive individuals, including against variants of concern,” the research team said.
