Herd immunity can’t be taken for granted yet, caution experts

Pune: Covid task force experts have cautioned against taking herd immunity for granted despite some sero-surveillance reports showing 50-60% of the people tested had antibodies.

“A cautious approach should be maintained despite these reports,” Niti Aayog member Dr Vinod Paul, also a member of the national task force, told TOI.

The national sero-survey report released by the Indian Council of Medical Research (ICMR) on Thursday stated that only 21% of the population showed evidence of past exposure to Covid-19. Paul said it meant a large proportion of the population was still vulnerable.

Scientists estimate 70-85% of people need to develop antibodies before Covid-19 wanes through herd immunity. Both natural immunity and vaccines can play a role in achieving it.

Dr Paul said the current sero-survey indicates the infection could spread to more than 75% population even now, hence it is crucial to follow Covid-appropriate behaviour. “A big proportion of our population is still vulnerable, and the national mission of vaccination will help overcome the pandemic in a better way,” he said.

State technical expert Dr Subhash Salunkhe stated there might be herd immunity, but only in certain pockets. He said the sero-surveys conducted in Delhi, Pune and Mumbai did show that 50% of those tested had developed antibodies, but the exact number of infections or even the antibodies created was still a grey area. “The only thing the country can do now is aim to vaccinate 30-40 crore of the population in the coming two to three months to ensure the pandemic becomes endemic,” he said.

ICMR’s chief epidemiologist Dr Samiran Panda said India is still a long way from achieving herd immunity.

Another public health expert, Dr Giridhara Babu, said it was implausible to infer the entire country had achieved herd immunity because of the diverse nature of the regions and populations within India. “At the most, we can infer dense pockets of urban areas have reached the threshold for population immunity.”