Covid: Covishield gives higher immune response than Covaxin, says study

Neutralising antibody responses against the Covid-19 virus and its variants has been found to be more effective with Covishield vaccine than the indigenously made Covaxin, according to a multi-centre study.

The study, posted on the preprint server MedRxiv on Friday (January 6), also found that when compared to pre-vaccination baseline, both vaccines elicited statistically significant antibody levels in both seronegative individuals and seropositive or those who had recovered from Covid-19 infection.

Researchers enrolled 691 participants in the 18-45 age group across four sites in urban and rural Bengaluru and Pune between June 2021 and January 2022.

Also read: COVID in China: WHO asks China to share regular updates

Participants got two doses of Covaxin after a gap of 28 days or two doses of Covishield three months apart.

The participants were sampled at six time points for antibody analyses and at four time points for cellular analyses.

Where both vaccines score well

Compared to pre-vaccination baseline, both vaccines elicited statistically significant antibody levels in both seronegative and seropositive individuals, the researchers found.

Also read: Mock drills held across 20,000 hospitals to check Covid preparedness

Covishield elicited immune responses of higher magnitude and breadth than Covaxin in both seronegative individuals and seropositive individuals, across cohorts representing the pre-vaccination immune history of the majority of the vaccinated Indian population.

Immunologist Vineeta Bal noted that there was a difference in the response to Covid vaccines in the young adult population, if individuals were already infected with SARS-CoV-2 and recovered (seropositives) versus not infected.

“In seronegatives, two doses of Covishield lead to higher magnitude of antibody levels in higher proportion of vaccine recipients as compared to Covaxin recipients,” PTI quoted Bal from the Indian Institute of Science Education and Research (IISER), Pune, and one of the study authors as saying.

Also read: COVID: Next 40 days crucial as India may see a spike in cases: Govt

“In terms of waning of immune response with time also Covishield vaccinated individuals retain antibodies in their blood for longer period in larger proportion of individuals,” she added.

The yet-to-be peer-reviewed study does not directly look for or document protection from Covid-19 in the recipients.

Study findings

“Levels of neutralising antibodies as well as T cell responses, according to different investigators, are indirect indicators of protection,” Bal was quoted as saying.

“The interim results so far show that Covishield vaccination induces robust neutralising antibodies against the original SARS-CoV2; Covaxin also does it but somewhat less efficiently.

“Against later variants of the virus such as Delta and Omicron, especially Omicron, neutralising antibodies triggered by Covishield are not as effective. However, they appear marginally better than in Covaxin recipients,” she added.

Prior studies comparing Covishield and Covaxin were limited to addressing only antibody responses and in particular in the healthcare worker population who were immunised prior to the Delta wave.

There is, however, limited data on cellular immune responses elicited by these vaccines and no direct head-to-head comparisons or stratification by pre-vaccination serostatus.

Vaccination following exposure to the Delta or Omicron variants of SARS-CoV-2 is likely to affect the quality, quantity and duration of immune responses.

(With Agency inputs)