NEW DELHI: The Delta variant of the Covid-19 coronavirus has been found to be a major factor for breakthrough infections — Covid infection in persons who have received one or both doses of the vaccine — among healthcare workers at the Institute of Liver and Biliary Sciences in south Delhi.
Vaccination of the hospital’s 1800 employees began on January 16, the first day of India’s inoculation campaign, and by April-end had administered the jab to nearly 1,600.
Despite the Covishield injection, hospital officials disclosed, nearly 10% of the employees tested positive for Covid.
The infection rate was significantly higher in doctors and nurses than in other hospital staff, possibly due to higher exposure.
When a genomic analysis of the swab samples of the infected healthcare workers was completed recently by Dr Rajesh Pandey and Dr Anurag Agarwal at the Institute of Genomics and Integrative Biology (IGIB), they found that 70% of the infections were caused by the Delta variant (B.1.617.2), a variant of concern that became the predominant cause of Covid cases in Delhi from March onwards.
Before that, Alpha and Kappa variants of the virus were the dominant strains.
Dr S K Sarin, director of ILBS, said the high rates of breakthrough infection caused by the Delta variant was a worrisome trend.
“It shows that the variants can breach the antibodies generated by the vaccines and the vaccines currently being administered may not offer sufficient protection against new mutant strains,” warned Sarin.
“There may be a need for strict double masking by healthcare workers despite vaccinations.” Sarin also mentioned that the clinical presentation of the Delta variant patients was more severe and the virus remained in the infected subjects for longer periods.
Unvaccinated and single dose recipients had a higher risk of infection compared with those who had received both the doses, said Dr Pratibha Kale, associate professor, department of microbiology, ILBS.
She added that fully vaccinated staff were better protected with higher humoral immune response.
The infection rate was significantly higher in doctors and nurses compared with other hospital staff, possibly due to higher exposure to the coronavirus, Dr Kale said.
According to Dr Ekta Gupta, professor of virology at ILBS, the variants of concern confer potentially lethal properties on the virus with dangerous consequences like high disease severity and transmissibility, reduced susceptibility to treatments and ability to evade natural or vaccine-induced immunity.
Delhi reported its first peak of Covid infection in June 2020.
The second and third peaks were reported in September and November last year.
The serosurvey report released in February 2021 showed more than 50% of the population had developed protective antibodies against Covid during the three peaks.
Notwithstanding, Delhi saw a fourth peaking from April onward, in fact, the deadliest yet.