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Covid vaccines not effective against new variants: Study

The sero prevalence fell to 22.9% in April 2021, which was about a one-third decline in 6 months.

Covid vaccines not effective against new variants: Study

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CHENNAI: The number of COVID-19 cases has declined to single digits in Tamil Nadu, after a sudden spike of cases due to the JN.1 variant last month.

The new variants raised questions over the effectiveness of vaccines and the need for booster shots but a recent study has shown that those vaccines are not helpful to fight the current variant.

A study titled ‘Contribution of infection and vaccination to population-level sero prevalence through two COVID waves in Tamil Nadu’, has found that the sero prevalence drops over time and antibodies wane away. Thus, the vaccines that were introduced and used when the pandemic hit initially would not be effective against the new variants now.For the study, the four rounds of serological surveys conducted in October 2020 and April–May 2021 across the State were analysed.

It was found that the State-level sero prevalence was 31.5% in October-November 2020, after the first wave in India. The sero prevalence fell to 22.9% in April 2021, which was about a one-third decline in 6 months. The antibodies formed due to the infection also dropped in the samples. The sero prevalence rose to 67.1% in June-July 2021, mainly due to the rise in infections of the Delta variant.

While the vaccinations paced up, the sero prevalence rose to 93.1% in December 2021-January 2022. However, the antibodies also appeared to wane after vaccination.

The sero prevalence in urban areas was higher than in rural areas, but the gap reduced over time. The key author of the study Dr TS Selvavinayagam, Directorate of Public Health and Preventive Medicine, said, “The immunity power that protected us during the pandemic due to vaccination or due to the previous infection may not be protective now, or in the future as new variants are emerging. However, there is evidence that it continues to protect against severe illness. At the same time, we need to understand that there is no need for booster shots at this moment as the virulence of the virus has reduced, and what we see today are milder variants.”

He cautioned those with co-morbidities like diabetes and hypertension to follow Covid protocol, as their risk of infection is very high. “Anyone with signs and symptoms of Covid should contact nearby a health system including Primary Health Centres, particularly in children and elderly, as they are more vulnerable,” he pointed out.

Shweta Tripathi
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