New Delhi: A small-scale study conducted on healthcare workers from the Fortis Centre of Excellence for Diabetes, Metabolic Diseases and Endocrinology in Delhi has found that 16 per cent tested positive for Covid-19 after being vaccinated.
This is within the promised efficacy of Covaxin and Covishield — the two vaccines being administered in India right now — which claim to offer a protection of 78 per cent and 79 per cent, respectively, against symptomatic Covid-19 disease.
The study, published in the peer-reviewed journal Diabetes and Metabolic Syndrome: Clinical Research and Reviews on 3 May, involved 110 employees of the hospital (doctors, nutritionists, nurses, paramedical workers, and maintenance staff), of whom 107 had received the second dose.
Breakthrough infections — Covid infection in vaccinated individuals — were observed in 18 people. As many as 94.5 per cent of the breakthrough cases detected were mildly symptomatic with a fever, with only one requiring hospitalisation.
As Covid vaccinations gain ground, breakthrough infections have emerged as a new area of study. V.K. Paul of the government think tank Niti Aayog said at a press briefing last month that the incidence of such infections is low. Saying the narrative on “breakthrough infections is distant from reality”, he added that such cases are not serious.
“Breakthrough infections are sometimes happening about 3-4 in 10,000. This happens in foreign vaccines also. This incidence is very low … even if Covid happens after vaccination, it does not become serious,” he had said. These numbers, he added, occur in high-risk populations such as healthcare workers, so “incidence among common people will be even lower”.
Speaking to ThePrint, Dr Anoop Misra, chairman of the Fortis Centre, said the study will be updated to reflect the latest numbers found by the hospital — one more case of infection was discovered when three other employees were tested. This means that of 113 individuals, he said, 19 had been diagnosed with symptomatic Covid-19. The number of people who had received the second dose remained the same at 107.
While 28 had received Covaxin, 85 had got Covishield.
“In 18 out of 19 cases, infection had occurred after the second dose, after a mean of 34.8 days (range 2-51 days),” Dr Misra said. “Breakthrough infections after 14 days of the second dose occurred in 15 persons (13.3 per cent).”
Covaxin and Covishield both have a two-dose regimen. Their efficacy kicks in at least two weeks after the second shot.
“Vaccines have effectiveness risk of getting Covid-19 infections by 70-90 per cent, and also shield from severe infection. It is possible, therefore, some people who are fully vaccinated against Covid-19 may get Covid-19 infection,” says the study.
Asymptomatic breakthrough infections a ‘concern’
The Government of India has defined breakthrough infections as those that occur two weeks after either dose of the two Covid vaccines.
“We have taken a more loose definition of breakthrough infections to include infections at any point after vaccination,” said Dr Misra. “Twelve of the 19 positive cases occurred among people less than the age of 40. All were symptomatic with a fever and half of them had sore throat and cough,” he added.
The study notes that though it is “reassuring” that the majority of breakthrough infections were mild, “a significant area of concern is that we may be missing asymptomatic infection since RT-PCR test was selectively done in symptomatic patients”.
“These asymptomatic patients with breakthrough infections are likely to promote viral spread,” it states.
“High prevalence of mild breakthrough infection is seen in our healthcare facility. Research in breakthrough infections in India should be extended to other institutions and community to obtain larger data,” says the study.
(Edited by Sunanda Ranjan)