The Covishield vaccine, manufactured by the Serum Institute of India, likely produces a greater number of antibodies than Bharat Biotech’s Covaxin, claims a pre-print of the first study involving healthcare workers that pits the two Covid-19 vaccines against each other in the country.
The study is currently undergoing peer-review and was conducted by A K Singh from G D Hospital & Diabetes Institute, Kolkata and six other experts. The study shows that both vaccines generated a good immune system response among doctors and nurses, but the level of antibody production differed.
The study tested the vaccines on 515 healthcare workers (305 male, 210 female), finding that, overall, both vaccines induced antibodies in 95 per cent of participants. Around 98.1 percent of those vaccinated with Covishield and 80 per cent of healthcare workers who received Covaxin showed seropositivity. The seropositivity rate, which refers to the production of antibodies, as well as the amount of anti-spike antibodies produced were significantly higher in Covishield as compared to Covaxin recipients.
The two vaccines are the most widely used in the country, which is struggling to ramp up the production of doses to stave off a potential third wave. So far, only 3.5 per cent of the population has received both doses of either vaccine, while close to 14 per cent have got at least one dose of either jab.
The scientists acknowledged in the paper that while the results may be surprising, to determine whether they were a result of having fewer Covaxin participants or intrinsic to the nature of the doses themselves would require more study. They also mention the findings of the study and efficacy do not necessarily predict efficacy.
The study’s authors also noted that Covishield produced a strong immune response even after the first jab, while antibody production in Covaxin recipients was weaker after the first dose but closed the gap after the second.
Significantly, the study also found that breakthrough infections — positive Covid-19 tests after two weeks of getting a jab — were lower in Covaxin recipients at 2.2 per cent, while Covishield takers showed a breakthrough infection rate of 5.5 per cent. This could indicate that Covaxin recipients may be less likely to contract the disease after two doses.
People over the age of 60 or those with type 2 diabetes had a significantly lower antibody production, the study also found.