Need to accelerate pace of vaccination in districts with low seroprevalence : NIE experts

‘Third wave in India will be much smaller than the second wave’

Districts with low seroprevalence and low COVID-19 vaccination coverage must be prioritised for targeted interventions such as vaccination. The areas where seroprevalence is low, the chances of virus spreading faster and emergence of new variants are high, experts of Indian Council of Medical Research (ICMR)-National Institute of Epidemiology (NIE) have said.

In an email interview, Manoj Murhekar, director of NIE and T. Jeromie, epidemiologist at NIE, outlined the need for Tamil Nadu to accelerate the pace of vaccination especially in districts where seroprevalence was found to be low since one-third of the population was still susceptible for infection, while continuing adherence to COVID-19 appropriate behaviour.

“The recent serosurvey conducted in the State indicates that around two thirds of the population has IgG antibodies against the virus. There is a wide variation in the seroprevalence between the districts, ranging from 37% in Erode to 82% in Chennai. It is reasonable to expect that the transmission will continue especially in districts with lower seroprevalence. The future surge of cases in the State is expected to be lower than the second wave. However, if a new immune escape variant emerges, we might see a bigger surge,” Dr. Murhekar said.

Noting that the districts with low vaccination coverage and with low seroprevalence of IgG antibodies are expected to see more cases, Dr. Jeromie said that the population in these districts was more susceptible for transmission, and hence, such districts need to be prioritised for both pharmaceutical and non-pharmaceutical interventions.

“The current R naught (basic reproduction number) for the State is 0.99 ,” he said.

Evaluating the State’s COVID-19 vaccination drive so far, he said that around 39% of the adult population in the State have received at least one dose of COVID-19 vaccine. “The availability of vaccines remains an important factor. Hence, prioritising districts with lower seroprevalence and individuals at higher risk of severe outcomes such as elderly, people with co-morbidity and pregnant women may be considered,” he said.

On whether they will be a third wave of COVID-19 infections, Dr. Murhekar pointed out that the fourth nation-wide serosurvey indicated that around two third of individuals aged six years and above in India have IgG antibodies against COVID-19. “Studies have shown that the immune response among the infected individuals is robust and antibodies last for at least one year. Re-infections are few among the already infected individuals. Studies also indicate that although the breakthrough infections are frequent among the vaccinated individuals; majority of these infections are mild and mortality among vaccinated individuals is very low,” he said.

Based on these findings, he noted that it was reasonable to believe that the third wave in India would be much smaller than the second wave. “However, with the emergence of new immune escape variant, one could see a high upsurge of cases,” he said

As of now, there was no new variant of interest found in the country, apart from the Delta variant, he said, adding: “We have to strengthen our genomic surveillance especially in areas with high number of breakthrough infections and hospitalisations, and also in high seroprevalence areas which are seeing surge of cases.”

Dr. Jeromie added that genomic surveillance was crucial at this phase of the pandemic. “We have to look out for new variants of interest and their ability to escape immunity. Information from the genomic surveillance will help us to plan to mitigate the future waves of the pandemic,” he said.

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