A recent study led by ICMR-regional medical research centre (RMRC), Bhubaneswar, has found the level of antibodies produced among the recipients of Covaxin starts to decline after two months, while the same for those who have been vaccinated with Covishield starts after three months.
ICMR-RMRC planned the study and formulated the methodology and was leading the study.
Talking to India Today TV, ICMR-RMRC scientist Dr Devdutta Bhattacharya said samples were collected from 614 participants for the study. Among these participants, 308 (50.2 per cent) were Covishield recipients and the rest 306 (49.8 per cent) got vaccinated with Covaxin. A total of 81 breakthrough cases were recorded among participants for whom infection post-vaccination acted as a booster, he said.
The remaining 533 healthcare workers without any history of post-vaccination infection showed significant decrease in antibodies, the study found.
This is a part of a long cohort follow-up study, he said, adding that they are planning to follow up for about two years to see the antibody persistence.
“We found that the antibody level of Covaxin recipients is decreasing after two months of complete vaccination, while it is three months in the case of Covishield recipients,” Dr Devdutta said.
The study was undertaken to determine IgG (Immunoglobulin G, the most common antibody) antibody among health care workers with completed dose of either Covaxin or Covishield. They were followed for 24 weeks after first dose of either vaccine to record the periodic changes in titre, concentration, clinical growth and persistence of vaccine-induced SARS-CoV-2 antibodies.
The study commenced in March 2021.
ICMR-RMRC, Bhubaneswar, Director Sanghamitra Pati, however, said that even if there is a decline in antibodies, there is persistence of antibodies and we keep on following them up.
In eight weeks, antibodies were found to be declining, she said and added that this will be followed up after six months and that there are plans to continue this over a period of time.
“Then only can we say whether a booster is required or not and if required, when,” added Sanghamitra Pati.