‘This’ Covid vaccine’s booster dose has best immune response, finds Lancet study


Covid-19 updates: The booster dose of Covishield vaccine, manufactured by Serum Institute of India Pvt Ltd in India, has the best immune response to the emerging threats of a Covid infection, a study published in The Lancet Regional Health Southeast Asia journal has revealed. 

The study says that irrespective of the patients primary which could be Covishield or Covaxin, it has been found that Covishield booster dose has the best immune repones. 

The study shows that boosting the vaccine response in an individual with Covishield produced better binding and functional antibodies than getting dised with a booster of any other vaccine. 

This revelation comes irrespective of the fact that homologous and heterologous boosting with Covishield or Covaxin in Covishield or Covaxin primed individuals are immunogenic and safe. 

Amid growing Covid-19 cases and emerging variants of the highly transmissible virus, it has been observed that primary SARS-CoV-2 vaccination wanes over time and thereby results in depletion of the individuals immune response to fight the emerging variants of coronavirus. 

At such a point a booster dose of the vaccine becomes imperative. The World Health Organisation (WHO) has highly recommend the administration of booster doses.

The study, conducted by researchers from Christian Medical College, Vellore, Tamil Nadu and Centre for Cellular and Molecular Biology, Hyderabad, Andhra Pradesh, determined the safety and immunogenicity of homologous or heterologous boosters with ChAdOx1 nCoV-19 (Covishield) or BBV152 (Covaxin), the two vaccines used widely for primary immunization in India, in participants who had already received two primary doses of these vaccines, it said.

Covishield and Covaxin are the two vaccines used in the majority of the Indian population. The four permutations for a booster dose evaluated in this study are primary immunization with Covishield followed by a homologous booster or a heterologous Covaxin booster and primary immunization with Covaxin followed by a homologous booster or a heterologous Covishield booster, the study said.

Participants primed with two doses each of Covishield or Covaxin 12–36 weeks previously, were randomised to receive either Covishield or Covaxin booster in a 1:1 ratio, the study said.

The primary outcome was day 28 post-booster anti-spike IgG seropositivity and secondary outcomes were anti-spike IgG levels and assessment of safety and reactogenicity. The results of 90 days intention-to-treat analysis are presented, the study said.

In the Covishield primed group with 200 participants, the seropositivity 28 days post booster in the heterologous Covaxin arm was 99 per cent and non-inferior to the homologous Covishield arm, which was also 99 per cent, the study said.

The geometric mean concentration (GMC) of anti-spike antibodies following heterologous Covaxin boost on day 28 was 36,190.78 AU/mL while the GMC following homologous Covishield boost was 97,445.09 AU/mL, the study said.

In the Covaxin primed group with 204 participants, the seropositivity 28 days post booster in the heterologous Covishield arm was 100 per cent and non inferior to the homologous Covaxin arm which was 96 per cent, the study said.

The GMC following heterologous Covishield boost was 241,681.6 AU/mL compared to homologous Covaxin boost, which was 48,473.94 AU/mL, the study said.

The day 28 geometric mean ratio (GMR) of the anti-spike IgG between the heterologous and homologous boosted arms was 0.42 in the Covishield primed group and 5.11 in the Covaxin primed group, the study said.

There were no related serious adverse events reported in any group, the study said.

The study found that a heterologous boost with Covishield after Covaxin prime offers the best immune response among the four combinations evaluated.

For both binding and functional antibodies, in participants primed with Covishield, homologous boosting with Covishield offers better immune responses than heterologous boosting with Covaxin; and in those primed with Covaxin, heterologous boost with Covishield offers the better immune response.

(With inputs from ANI)

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