The severe COVID-19 outbreak seen in Delhi in 2021 indicates that the Delta variant of the coronavirus can infect those who have been previously infected by a different variant of SARS-CoV-2, and brings to light the challenges in reaching herd immunity against the variant, suggested a new study.

The study noted that the Delta variant was around 30-70% more transmissible compared to the previous lineages of the virus circulating in Delhi. The authors noted that the city’s overall seropositivity was 56.1% which could have conferred some protection from future outbreaks through herd immunity. The study was conducted by the National Centre of Disease Control and the Council of Scientific and Industrial Research-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi, in association with the University of Cambridge and Imperial College London, UK, and the University, Copenhagen, Denmark.

Previous infection was found to yield only 50-90% of the protection against the Delta variant that it provides against previous lineages. The findings were published in the journal Science… (ET Healthworld – PTI, October 16, 2021)