Study reveals 95% seropositivity after two doses of Covishield, Covaxin


A new pan India study recently revealed that out of 515 healthcare workers, 95 percent showed seropositivity after two doses of Covishield as well as Covaxin. Out of 425 Covishield and 90 Covaxin recipients, 98.1 percent and 80 percent, respectively, showed seropositivity, stated the study published in preprint server medRxiv on June 4.

Seropositivity means having the presence of antibodies in blood serum. Dr. Awadesh Kumar, the lead researcher of the study from GD Singh Hospital and Diabetes Institute, said the study found that both vaccines were equally good and could produce high antibodies even after a single shot.

The study was conducted across 13 states and 22 cities and found that the vaccines could generate an immune response in 95 percent of recipients, 21 to 36 days after the second dose. Seropositivity was observed in 98 percent of those immunized with Covishield as opposed to 80 percent in Covaxin recipients.

“Our primary aim was to analyze antibody response (seropositivity rate and antibody titre) following each dose of both vaccines and its correlation to age, sex, blood group, body mass index, and co-morbidities,” researchers said.

Anti-spike antibody titre is being measured at four time points: day 21 after the first dose until the day before the second dose; day 21 to 28 of the second dose; day 83 to 97 (three months) and day 173 to 187 (six months) after the second dose. 

Second blood samples (5 ml) were collected from those eligible from day 21 to 36 after the second dose of each vaccine. A total of 515 (305 male, 210 female) participants took part in the study, of which 425 and 90 received both doses of Covishield and Covaxin, respectively.

The seropositivity rate was significantly higher in Covishield as opposed to Covaxin recipients (98.1 percent v 80 percent, respectively). The Seropositivity rate was significantly more in participants aged above 60 (96.3 percent) as opposed to 87.2 percent in those aged below 60, in overall cohorts, primarily contributed by Covishield recipients, authors stated. Breakthrough infections were noted in 5.5 percent (22/399) cohorts in Covishield and 2.2 percent (2/93) of Covaxin recipients. The majority had mild (28/30) to moderate (2/30) Covid-19 infections and all. 

Dr. Samiran Panda, head of epidemiology and communicable division at Indian Council of Medical Research, said that they were looking at a population level data, and taking samples from a certain group (like healthcare workers, for instance, in this study) may not indicate an extrapolation of inference in a wider group of people.

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By TIS Staffer
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