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30% Individuals Lose Vaccine-acquired Immunity After 6 Months: Study

The study was designed to understand the longevity of vaccine immunity in Indian population.

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AIG Hospitals along with the Asian Healthcare Foundation has published results of another significant research in which long-term durability of vaccine immunity was accessed with respect to the antibody levels. The study was conducted on a large pool of 1,636 healthcare workers who were fully vaccinated.

“We are seeing a surge of infection across the country. Fortunately, the severity of the disease is mild because of multiple factors including the effect of vaccination, the intrinsic character of the variant itself and natural immunity amongst the population. However, we need to devise strategies that can ensure minimal spread and protect as many people as possible. The study aimed to understand the effectiveness of current vaccines over the long-term and see if there are specific population demography who need a booster at the earliest,” Dr D Nageshwar Reddy, Chairman, AIG Hospitals said.

Researchers involved in the study measured the IgG anti-S1 and IgG anti-S2 antibodies to SARS-CoV-2 in those 1,636 individuals. Those who had antibodies levels less than 15 AU/ml were considered antibody negative, which means they didn’t develop any protective immunity against the virus. Further, it was estimated that an antibody level of 100 AU/ml is the minimum level for protection against the virus, which means any individual with less than 100 AU/ml antibody level is susceptible to getting infected.

Of the 1,636 study participants, 93 per cent (1,519/1,636) had received Covishield, 6.2 per cent received Covaxin (n=102) and <1 per cent received Sputnik (n=13).

“Our study results were at par with other global studies where we found that almost 30 per cent individuals had antibody levels below protective immunity level of 100 AU/ml after 6 months. These individuals were majorly above 40 years with co-morbidities like Hypertension and Diabetes. Out of the total, 6 per cent did not develop any immune protection at all,” said Dr Reddy who is also amongst the researchers.

The results clearly indicate that with age, immunity wanning is directly proportional which means that younger people have more sustained antibody levels than the elderly population. One of the most important results of the study showed that people above 40 years with co-morbidities like Hypertension and Diabetes have significantly less antibody response after 6 months of getting fully vaccinated. Therefore, individuals above 40 years with diabetes and hypertension of both genders may be at a higher risk of SARS-CoV-2 infection and these individuals should be prioritised for a booster dose after 6 months.

“At present, the 9-month gap for prevention dose benefits 70 per cent of the population who can retain enough antibody levels beyond 6 months. However, considering the scale of our country, the 30 per cent people especially those with co-morbid conditions like Hypertension, Diabetes, etc, who are more prone to develop an infection after 6 months of getting fully vaccinated should also be considered for the prevention dose,” Dr Reddy further added.