"Significant" antibody waning, four months after the first dose- says study conducted in India

A research study conducted in India, where 614  fully vaccinated health workers were studied, revealed a “significant” drop in Covid-19 fighting viruses antibodies, four months after the first dose.

As of now, the vaccine roll-out in India which began in mid-January is supposed to be the only antidote against SARS-CoV-2. The findings of these studies can now help the Indian government decide whether a booster shot is necessary for Indian citizens, as has been decided by many western countries.

However, waning antibodies does not mean that vaccinated individuals lose their immunisation and ability to fight the disease, confirmed the doctors of the state-run institution conducting the study. They added that the body's memory cells may still kick in to offer substantial protection

British research last month also revealed that protection offered by two doses of the Pfizer and the AstraZeneca vaccines begins to fade within six months.

In the study, a cohort of 614 health workers who completed both the doses of their immunisation subsequently, was followed for 24 weeks after the first dose to monitor the periodic changes in titre, concentration, clinical growth and persistence of vaccine-induced SARS-CoV-2 antibodies.
Serum samples were collected of these 614 individuals, in every follow-up and tested in two CLIA-based platforms for SARS-CoV-2 antibodies, both quantitatively and qualitatively.

The research which is published revealed that out of the 614, 308 where (50.2%) were Covishield recipients and the rest 306 (49.8%) took Covaxin. A total of 81 cases were seen as breakthrough cases in the cohort for whom infection post-vaccine worked as boosters to their immunity. While the rest of 533 healthcare without any history of post-vaccination infection, showed significant antibody waning, in both Covaxin recipients and Covishield recipients.

However, the researchers still concluded that “The clinical implications of waning antibody levels post-vaccination are not well understood”. Emerging evidence suggests that antibodies are important in blocking infection and transmission of the virus, however, the threshold associated with protection against clinical outcomes is still not established.

The study concluded that its findings point towards studying a larger cohort which would help researchers better understand the correlates of protection and determine the requirement of better vaccines or booster doses.

This research was one of its kind in India which involves studying the effectiveness of the two main vaccines, Covaxin and Covishield.

The Indian study, published in the Research Square pre-print platform was ethically approved by the Institutional Human Ethical Committee of ICMR – Regional Medical Research Centre, Bhubaneswar, but is yet to be peer-reviewed.

The researchers have a follow-up plan for two years which will further help in understanding the kinetics model and also to provide a better estimate of the antibody response in both Covid-19 positive and negative individuals over a significant period.