A study by the ICMR on COVID-infected individuals in the city has indicated that the prevalence of B.1.617.2 (delta variant) "was not different between the vaccinated and unvaccinated groups."

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B.1.617.2, or the delta variant of COVID causing Sars Cov2 was the dominant circulating strain and one of the primary drivers for the country's COVID second wave, the study, approved by the ICMR-National Institute of Epidemiology, Chennai, said. Those involved in the study include researchers from the National Institute of Epidemiology, here.

COVID-infected persons, both vaccinated and unvaccinated ones, who visited the Greater Chennai Corporation's triage centres between May 3 and 7, were enrolled in the study. "The study findings indicate that the prevalence of B.1.617.2 was not different between the vaccinated and unvaccinated groups. Delta variant was the dominant circulating strain and one of the primary drivers for the second wave ofRS-CoV-2 in India. Studies have documented a reduction in neutralisation titres among Covishield and Covaxin recipients after infection with delta variant. This might be the reason for the breakthrough infections observed in the fully vaccinated individuals," it said.

However, the proportion of patients progressing to severe illness and mortality was lower in the vaccinated groups, it added. While B.1.617.2 has the potential to infect both the vaccinated and unvaccinated individuals, however, the progression of illness seems to be prevented by vaccination. "Therefore, non-pharmaceutical interventions must continue to slow down the transmission. Additionally, the pace and scale of vaccination has to be increased to mitigate the further waves of the pandemic," it said.