A third booster shot is necessary to maintain the protective antibodies against Covid-19, an Israeli study published in the New England Journal of Medicine claimed. The study was conducted on 5,000 Israeli health workers who had received shots of the Pfizer-BioNTech vaccine and found that the overall levels of the antibodies dipped sharply in the first few months after the vaccination and fell at a moderate pace.
The study would help scientists identify the critical threshold of antibodies needed to prevent re-infection by Covid-19 in individuals who had received the vaccine, study author Gili Regev-Yochay said in a press conference held on Wednesday. In addition to this, the study found that antibody levels in men were lower than in women both when the levels peaked and when they dropped to a minimum. Antibody levels were found to be lower in older people than in younger, and in immuno-suppressed individuals compared to the healthy population, according to the study from Sheba Medical Center in Ramat Gan.
Still, the research found, prevention of severe and fatal infections remained strong throughout the study period, reaching 96% in the first two months after the second dose and persisting at roughly this level for six months. A similar study from Qatar published in the same journal showed a decrease in vaccine protection, from 77.5% during the first month after the second dose to 20% in months five to seven after the second dose. The study was conducted over a similar time frame to the Israeli one.
Israel will offer a third booster dose of the vaccine to its population for which studies like this are crucial for maintaining low levels of death and hospitalisation, the study authors said.