Herd immunity achieved in Tamil Nadu at last, say experts – Times of India

Chennai News
CHENNAI: Herd immunity is here — and this could be why crowding during Diwali shopping, New Year revelries and Pongal festivities did not push up the epidemic curve in the state, say public health officials and scientists.
At least 31.6% of people in TN have developed antibodies for Sars-Cov2, the virus that causes Covid-19. The population-level sero-prevalence survey of 26,640 adults across the 37 districts between October and November 2020 estimates at least 22.6 million infections in the state – higher in cities and among those who are working. “But the epidemic was largely silent in many districts,” said director of public health Dr T S Selvavinayagam.

For instance, Perambalur, which has five active cases and has reported fewer than six cases a day in 2021 has a seropositivity of nearly 50%, the highest in the state. The district’s case tally was 0.3% of the state’s cumulative tally since March 2020. On the other hand, the Nilgiris, which follows natural social distancing given its landscape, had the lowest seropositivity of 11%.
“These are extremely good and encouraging results,” said senior epidemiologist Dr Jayaprakash Muliyil, who chairs the scientific advisory committee of the National Institute of Epidemiology. “This is because any sero survey underestimates the positivity rate. We are seeing a steady fall in cases from September. The epidemic is over. And it happened even before the vaccines came in. We should not wait for the last case to call it the end, because that may not happen anytime soon.”
Senior virologist Dr T Jacob John gave two reasons for the huge difference in antibodies in different parts of the state — the antibodies may have diminished in some people who had the infection early and may be higher than expected in some cases because of more recent recoveries.
Officials fear that the waning antibodies and new variants of the virus could be emerging threats even as they battle vaccine hesitancy. “Second wave in countries like Brazil is an example of how powerful the virus is. We still need masks, social distancing, fever surveillance and testing. We also need more people to vaccinate themselves,” said health secretary J Radhakrishnan.
The state health department is also planning a second sero-surveillance study to see if antibodies to the novel coronavirus will stay on despite a swift fall in cases over the last few weeks, he said. “Testing will tell us the infection rate in the population — where it’s higher, where it’s lower. As we reopen more places, we can watch the infection rate to see if it’s going up and if it is, slow down. We will be able to study the effect of vaccines as well,” he added.
While scientists insist that the government must not drop the guard, they said some of their worries were overblown. “Antibodies will drop after the body clears an infection. But science has told us that with its memory, the body’s immune cells can create fresh antibodies when needed,” said Dr Muliyil. “As of now there is no evidence of a powerful variant that can breach the immunity of an old infection. If there is one, we have to trust the immunity again. Technology is also advanced to help scientists reshape the vaccine to cover more variants.”

Source: https://timesofindia.indiatimes.com/city/chennai/herd-immunity-achieved-in-state-at-last-say-experts/articleshow/80775288.cms