A study on a group of fully vaccinated health workers in India has found a significant drop in Covid-fighting-antibodies within four months of receiving their first dose.
The data is expected to help the Indian government take a decision whether to provide booster vaccine doses, reported Reuters.
India had begun the Covid-19 vaccine rollout in mid-January this year.
The study was conducted to assess the dynamicity of vaccine-induced IgG antibody against SARS-CoV-2.
The cross-sectional cohort study was designed to determine IgG antibody among health care workers with completed dose of either Covaxin or Covishield.
The participants were observed for 24 weeks after first dose of either vaccine.
The study recorded the periodic changes in titre, concentration, clinical growth and persistence of vaccine-induced SARS-CoV-2 antibodies.
Serum samples were gathered from 614 participants during each follow-up and tested in two CLIA-based platforms to evaluate antibodies in terms of quality and quantity.
Out of the total participants, 308 (50.2%) were Covishield recipients and 306 (49.8%) Covaxin recipients.
The study revealed that only 81 breakthrough cases of the total participants for whom infection post vaccination served as a booster.
For the remaining 533 heath care workers without any history of post-vaccination infection, a significant antibody decline was seen from 12 weeks in Covaxin recipient or 16 weeks in Covishield recipient.
The study concluded that the clinical implications of declining antibody levels post vaccination are not clearly understood and therefore, it is essential to establish S-antibody thresholds related to protection against clinical outcomes.
Published in the Research Square pre-print platform, the study is yet to undergo a peer review.
Conducted from 16 January to 31 July 2021, the study had participants from six institutes in Odisha state and was approved by the Institutional Human Ethics Committee of ICMR – Regional Medical Research Centre, Bhubaneswar.
