‘Covaxin produces better response against COVID’

Scientific experts had pointed out that the Lancet study on Covaxin misses the very crucial T lymphocytes angle but a separate study published in a nonpeer reviewed international publication medRxiv on November 15 reveals that the vaccine provides a TCell response in the human body helping it to fight the COVID19 virus betterA team of scientific experts from National Institute of Immunology NII New Delhi and All India Institute of Medical Science New Delhi and some others conducted the studyHowever as the study has taken into account a small number of beneficiaries health experts say a clearer picture of TCells would be ascertained only after regular monitoring of the patients which should be done continuously for a few years This would help in indicating the longterm efficacy of the vaccineDr Wiqar Shaikh professor of Medicine Grant Medical College and JJ Group of Hospitals said that in two earlier articles midday had highlighted the need to study the TCell cellmediated immune response of the human body following administration of COVID19 vaccines He added that it was particularly needed for Covaxin to demonstrate to the world that a COVID19 vaccine researched and manufactured in India possessed allround and robust efficacyHe further said ldquoIn a viral infection antibodies produced by the human body attack and attempt to eliminate the virus However once the virus enters the human cells antibodies have no role in defence and TCell immunity becomes the bodyrsquos sole weapon This is the job of two types of TCells ndash the Natural Killer NK cells and the Cytotoxic cellsrdquo Dr Shaikh added ldquoThe medRxiv study on Covaxin concludes that the vaccine induces memory B cells which are similar to those seen in human beings following natural COVID infection Besides the study also shows the presence of TCells in 85 per cent of the beneficiaries who have been studied Both antibodies and TCell responses are concurrent Also following Covaxin administration antibodies are detectable for up to six months This study shows that the vaccine induced a low magnitude of neutralising antibodies but produced a potent TCell response particularly against COVID19 variants This puts Covaxin on a high pedestal amongst all the COVID vaccinesrdquoHe said that one drawback of the study was the sample size Only 71 subjects who had received two doses of Covaxin were included in the study The other limitation he said was that medRxiv is a nonpeer reviewed journalSpeaking to midday Dr Subhash Hira professor of Global Health at the University of WashingtonSeattle and an invited expert to several WHO COVID review forums said ldquoIt is a small sample study of 71 volunteers who took two doses of Covaxin and a separate cohort of 73 nonvaccinated individuals who got infected with mild COVID19 and tested positive Both groups were followed for six months to compare safety and immunogenicity of vaccineinduced infection and natural COVID19 infection This appears to be a supplementary study since the authors had already published a Phase 2 safety and immunogenicity study in the Lancet at a threemonth interim followup of vaccinesrdquoldquoThe vaccines were well tolerated and did not report any serious side effects The limitations of such small size studies is that these provide basic information of safety and immunity accorded by the vaccines as compared to immunity generated by natural infections However detailed immunologic investigations in a prospective largesized study is required wherein vaccine volunteers are followed up after every quarter for 1824 months or even longer to establish neutralising antibody levels increase in CD4 cell count after Covaxin injections and role of memory Tcells that remain stored in body reservoirs The memory cells get activated when any possible breakthrough natural infection occurs in individuals caused by the original virus or its new variants during the followup period of 1824 months This is then quantified in the laboratoryrdquo added Dr HiraHe further said ldquoBharat Biotech is on record testing diluted forms of Covaxin for children between 215 years of age and for pregnant women It is also trying to find out whether an intranasal spray can be made so that the vaccine can be administered without a syringe The aim is to identify vaccines that can provide cellmediated immunity by memory TCells for a lifetime These are exciting times for innovationdriven companies like Bharat Biotech to take the global leadership and expand its pool of global scientistsrdquo