Coronavirus | Antibodies from COVID-19 infection appear earlier, finds study

An elderly person being administered Covid-19 vaccine at JP Hospital in Bhopal on Wednesday.   | Photo Credit: A. M. FARUQUI

Antibodies from a COVID-19 infection begin to appear significantly only 14 days after a vaccine jab. But in people who have already been infected by the virus before, the increase can be observed in a week, a study has found. While underlining the importance of the follow-up second shot, scientists associated with the study suggest that, in mass vaccination campaigns, individuals who have been exposed to the virus could be prioritised lower than those who have remained unexposed.

Also read: Study shows COVID-19 triggers antibodies from previous coronavirus infections

According to several serology surveys, anywhere from 21%-60% of India may have already been exposed to the virus since March. While India currently does not face supply constraints — there are more vaccines available than those registering for shots as of now — this could change as more groups become eligible for the vaccine. Currently, only healthcare, frontline workers, those above 60 years, and those above 45 years with co-morbidities, are eligible for vaccines.

The study, yet to be formally published but available as a preprint, measured antibodies generated in 135 healthcare workers administered with Covishield at different weeks or time points (0, 7, 14, 28 days). A third of the workers had already been exposed to the virus and in them, the antibody response progressively increased at each of those time points. In contrast, the antibody response started to show only after 14 days or later in 88 of the rest, who had been unexposed to the virus. Three did not develop any antibody response even at day 28 of vaccination. Currently, India’s recommended dosage schedule for Covishield and Covaxin is a spacing of four to six weeks.

The results also showed that antibodies in those infected earlier started to stabilise, even decline, after day 14 but were still substantially higher — in one instance nearly thousand-fold at day 28 — than those who were inoculated with Covishield but with no prior exposure to the virus. Currently, the longevity of antibodies after a COVID-19 infection has not been firmly established, nor is the immunity after being exposed to a particular strain of the virus.

“Our data suggests that ChAdOx1 (or Covishield) is highly immunogenic, particularly so where previous SARS CoV2 antibody-response is established. Given the high background seropositivity in India, this may be useful in determining optimal timing of the second dose during mass immunization within the constraints of vaccine supply and administration,” say the authors, comprising scientists from the Council of Scientific and Industrial Research-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi and the Max Group of Hospitals.

“We were surprised by the number of antibodies generated in those already exposed to the infection. This was the first time we used an antibody test that quantified the number of antibodies generated in response to the spike protein of the coronavirus,” Shantanu Sengupta, Scientist, CSIR-IGIB, told The Hindu.

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Printable version | Apr 11, 2021 7:06:19 PM |

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