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Covid-19: Vaccine-induced immunity in 30% individuals wanes after six months, new study finds

Individuals with antibody levels below 15 AU/ml were considered to be antibody negative, meaning they didn’t develop any protective immunity.

The study was conducted by Hyderabad-based AIG Hospitals, in collaboration with the Asian Healthcare Foundation. (File)
The study was conducted by Hyderabad-based AIG Hospitals, in collaboration with the Asian Healthcare Foundation. (File)

Antibody titres in 30% individuals above the age of 40 decline barely six months after vaccination, a new study has demonstrated.

The study was conducted by Hyderabad-based AIG Hospitals, in collaboration with the Asian Healthcare Foundation. The study evaluated antibody levels to SARS-CoV2 in 1,636 fully vaccinated healthcare workers to determine the longevity of vaccine-induced immunity and protection against Covid-19.

AIG Hospitals Chairman Dr D Nageshwar Reddy said despite a surge in infections across India, the severity of the disease had been mild due to a multitude of factors such as the effect of vaccination, natural immunity among the population, and the intrinsic character of the variant.

However, there is a need to formulate strategies to ensure minimal spread, Dr Reddy said. The study aimed to understand the long-term efficacy of current vaccines and see if there was a specific demographic that needed a booster shot at the earliest.

For the study, researchers measured the IgG anti-S1 and IgG anti-S2 antibodies in the 1,636 individuals. Individuals with antibody levels below 15 AU/ml were considered to be antibody negative, meaning they didn’t develop any protective immunity against the virus.

The coronavirus’ Omicron variant, first detected in South Africa, has sparked a rapid surge in Covid-19 cases in India and several other parts of the world. The variant has been found to transmit more easily than previous mutations and can evade vaccine-induced or natural immunity caused by prior infection. However, the variant is also said to be less severe and causes fewer hospitalisations and deaths.

India reported 317,532 fresh infections, with 9,287 Omicron cases, in the past 24 hours, according to Union Health Ministry data. The number of active cases surged to the highest in 234 days. The government said active cases now accounted for 5.03% of the country’s total infections, while the national recovery rate fell to 93.09%.

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