Hyderabad: With India launching the precautionary third dose of COVID-19 vaccine after a nine-month gap, the question of how effective the vaccine is, has resurfaced.
More so as the country is in the midst of a third wave of COVID-19 pandemic, driven by the Omicron variant.
In a significant research, it has been found that antibody levels in about 30% of vaccinated individuals dropped below the necessary protective immunity level after six months.
Hyderabad’s AIG Hospitals conducted the study with Asian Healthcare Foundation to assess long-term durability of vaccine immunity vis-à-vis antibody levels.
A total of 1,636 fully vaccinated healthcare workers were studied by the team of researchers. Of the participants, 93% received Covishield, 6.2% Covaxin and less than 1% got the Sputnik jabs.
“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,” explained Dr D Nageshwar Reddy, Chairman, AIG Hospitals.
The IgG anti-S1 and IgG anti-S2 antibodies to SARS-CoV-2 were measured in the 1,636 individuals.
“Those who had antibody levels less than 15 AU/ml were considered Antibody negative, which means they didn’t develop any protective immunity against the virus,” explained Dr Reddy.
It was estimated that 100 AU/ml is the minimum antibody level necessary for protection against the virus.
“Any individual with less than 100 AU/ml antibody level is susceptible to getting infected,” said Dr Reddy, one of the researchers.
“These individuals were majorly above 40 years with comorbidities like hypertension and diabetes,” informed Dr Reddy, adding that 6% of participants did not develop any immune protection at all.
Younger people, thus, have more sustained antibody levels compared to the elderly population.
Those above 40 (both genders) with comorbidities are at higher risk of contracting coronavirus. Hence, this category should be administered a booster dose after 6 months, the study suggested.
The 9-month gap between the second and third dose, which is being followed in India, benefits 70% of the eligible population who are able to retain enough antibody levels beyond 6 months, Dr Reddy said.
