Covid Booster Shot Required, Protection Diminishes Within 6 Months After 2nd Dose Of Vaccine: Study

A new study has said boosters are necessary after receiving the second dose of the Covid-19 vaccine because the immunity administered by the second shot wanes within six months.

A representational image of Covid-19 vaccine shot | Photo: Getty

New Delhi: A new study of about 5,000 Israeli health workers, published in the New England Journal of Medicine, has found that there is a continuous decrease in protective antibodies during the six months after the second dose of the Covid-19 vaccine is administered. 

The research states that boosters are necessary, because the immunity wanes significantly within months. Men were found to have less protection compared to women, due to less antibody counts, both at the peak and at the end of the study.

The study participants had taken Pfizer and BioNTech shots. 

Decrease in antibody levels after second dose

At first, there was a sharp decline in the levels, followed by a moderate decline.

One of the authors of the study, Gili Regev-Yochay, said that studies to identify the critical threshold of antibodies necessary to prevent coronavirus infection are important because this will help assess risk levels and find protective measures.

According to the study conducted by Sheba Medical Center in Ramat Gan, older people had lower antibody levels in their blood compared to younger people. Also, the antibody levels in immunosuppressed people were less compared to the healthy population. 

According to a report in Bloomberg, Regev-Yochay said in an online press briefing that the research helped them understand the cause of breakthrough infections in people who had received both doses of the Covid-19 vaccine. She added that the US is likely to follow Israel's decision to offer a third dose to everyone.

She said that she would be more than surprised if a lot of breakthrough infections do not occur in the United States. Also, the country has restricted booster recommendations for the older community and vulnerable groups.

Another study conducted in Qatar, published in the same journal, found the efficacy of the Pfizer-BioNTech shot to fade over a similar time period. During the first month after the second dose, the protection level was found to be 77.5 per cent. Five to seven months after the second dose, the protection fell to 20 per cent.

However, the strength of prevention of severe and fatal infections was 96 per cent in the first two months, and remained at roughly this level for six months, the research found.

Study co-author Laith Abu-Raddad said that the data is consistent, and that protection against hospitalisation and death is very strong, and more durable than protection against infection, mentions the Bloomberg article. He added that a third booster shot would help optimise the protection from the vaccine.

Other related studies

The Bloomberg article also mentions other studies from Israel published in the same journal, which state that there are certain cases of people suffering from heart inflammation after vaccination. Cases of young male recipients experiencing myocarditis after receiving the vaccine were reported, which were mostly mild, according to one study. However, one of the young male recipients died due to this inflammation.

Estimated incidence of myocarditis was found to be 2.13 cases per 100,000 persons, with most cases being mild or moderate, according to a study conducted by the Clalit Health Services, which is the largest health-care system in Israel.

Male patients aged between 16 and 29 showed the highest incidence.