A single dose of Covishield, vaccine for COVID-19 does not offer any significant protection against the deadly virus, a study has concluded. The study, carried out among healthcare workers, said that there was no major difference in the incidence of infection among those who had received only one dose of the vaccine and those who had not received any.

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The study among healthcare workers in Delhi’s Sir Ganga Ram Hospital was conducted between March 1 and May 31 among 4,276 employees of the hospital by a team led by Dr Ruma Satwik, reports The Indian Express.

The study included 2,716 employees who had received two doses of Covishield, 623 who had received a single dose, and 927 who remained unvaccinated. Of these 560 or 13.1 % of the 4,276 employees tested positive for COVID-19 — 1.8 % of these were asymptomatic, 81.79 % had mild disease, 10.2 % had moderate disease, and 4.64% had severe disease. The study was underway during the city’s deadly second wave. 

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The incidence of infection among those not vaccinated and those who had received a single dose was almost the same — 13.9% and 12.3 % respectively. This marginal difference continued in the incidence of moderate to severe disease, which was 2 %  among the single dose group and 3.3 %  among the unvaccinated group. Further, 0.7 % of the single dose group required supplemental oxygen as compared to 1.7 % the unvaccinated group, the newspaper reports.

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The study also concluded that the fully vaccinated had higher levels of protection against the virus. It was also observed that those who had been previously infected with the virus had significant protection.

The lead author of the story, Dr Ruma Satwik told The Times of India (TOI) that their study revealed that a single dose offered very little protection against the virus and the risk of developing severe symptoms or death due to COVID-19 are high.