Experts divided over T-cell data in The Lancet study

After the WHO green light to Covaxin and the subsequent publication of its phase3 efficacy data by The Lancet last week health and vaccine experts say this would boost the ongoing clinical trials of muchawaited vaccine protection for paediatric age groupmdash2 years to 15 yearsmdashand pregnant women Health experts are however divided over the ldquomissing Tcellsrdquo in the prestigious medical journalldquoIt is indeed a proud moment for India especially with the indigenously made Covaxin getting the final approval for usage though it took longer for approval The ongoing clinical trials of paediatric and vaccine for pregnant women are two more challenges towards universal vaccination against Covid which if successful could be launched by June 2022 and it will add another feather in the cap of Indiardquo Dr Subhash Hira Professor of Global Health at the University of WashingtonSeattle and invited expert to several WHOGenevarsquos Covid review forumsDr Jacob John virologist from VelloreUnlike other global vaccines which are fractionated genomic vaccines Covaxin is a firstofitskind inactivated whole virus vaccine he said lauding that the homegrown vaccine was a selffunded RampD compared to global vaccines supported by foreign governments While many global vaccines are 2035 per cent effective against Delta variants Covaxin scored an impressive 65 per cent he said Dr Jacob John a worldrenowned virologist from Vellore had similar views on Covaxin ldquoAmong all currently WHOapproved vaccines Covaxin is easily the safest This seems to come out clearly in the AEFI reports from the Task Force alsordquo he saidOn the lack of funding for Covaxin he said ldquoGovernments usually do not support private companies In the early days of the pandemic the Government of India wanted to control Covid without a vaccinerdquo On the comparable efficacy of vaccines at large Dr John said ldquoWhen two vaccines have comparable efficacy safety metric will compel you to go for the safer vaccinerdquolsquoMissingrsquo Tcell in Lancet reportDr Wiqar Shaikh professor of medicine at Grant Medical College and JJ Group of hospitals has stressed that vaccine efficacy cannot be measured alone through neutralising antibodies but should also include T lymphocytes studies mainly natural killers like Tcells and cytotoxic Tcells ldquoIt is still unclear if Bharat Biotech had done the Tcell study in phase 1 and phase 2 It is unclear why such a crucial part of the immunological analysis was missed out in phase 3 under the ambit of tagging it as mere lsquoefficacy trialrsquordquolsquoP3 trial focussed on diseaserelated end pointsrsquoAbout missing Tlymphocytes in calculating Covaxinrsquos efficacy Bharat Biotech said ldquoWe agree with the point indicating the importance of Tcell response in viral vaccines Apart from neutralisation antibody titers we have also done extensive studies to evaluate cell mediated responses in our various clinical trials with Covaxin Please refer to Phase I and Phase II publications wherein IFNg secreting Tcell responses polyfunctional Tcell responses by measuring various cytokines and Tcell memory response were reported For Phase III being an efficacy trial we focused mainly on diseaserelated end points and measured the efficacy in terms of preventing symptomatic and severe Covid19rdquolsquoAntibodies corroborate efficacyrsquoDr Jacob John differed from the Tcell argument calling it ldquoillustrative of book knowledgerdquo He said most immunity surveysmdashfor polio measles varicella rubella hepatitis etcmdashare done by measuring antibody prevalence ldquoVaccine efficacy measures the reduction of disease incidence by vaccine immunity Virus neutralising antibodies corroborate efficacy Expecting Tcell immunity measurements in the phase 3 vaccine trial thousands of subjects is out of poor understanding of vaccine clinical trials Tcell immunity studies in clinical medicine is either for research or for assessing the immune system in suspected immunodeficiencyrdquo said Dr JohnldquoDuring vaccine design and development they showed that the novel adjuvant is effective as evidenced by good T cell response That clinches sciencerdquo Dr John concluded Dr Hira said ldquoSmaller studies of Tcell mediated immunogenicity and safety studies were completed for all vaccine candidates during Phase1 and Phase2 studies There is a definite need to monitor Tcell counts as the indicator of longterm efficacy of vaccines in a fullfledged vaccine trial at a later date and also should include correlation with a full list of lsquovariants of concernrsquordquo The studies are done using the WHOCDC templatedesigns he saidGovt support mustDr Santosh Bansode Head of the Department Emergency Medicine Wockhardt hospitals said foreign pharma companies that got money from their governments had orders even before publishing trial data ldquoThat was not the case with Covaxinrdquo he said ldquoGovernment should invest in Indian research and development without expectations of absolute gain from it because diseases like Covid will keep coming and we need strong research and development to deal with such diseases Funds help to carry out research at a faster rate and produce data in a transparent manner to international agencies So that approval can be achieved for its worldwide userdquo said Dr Bansode adding ldquoIf we really want to see Atmanirbhar Bharat we must support our research and development in all possible waysrdquoWhy Tcells matterWhat are TcellsTcell also called T lymphocyte a type of white blood cell is an essential part of the immune system Tcells are one of two primary types of lymphocytes that determine the specificity of immune response to antigens or foreign substances in the bodyCan Tcells fight CovidScientists are hopeful that Tcells mdash a group of immune cells that can target and destroy virusinfected cells mdash provide longterm or lifelong immunity against Covid19 even if antibodies become less effective at fighting the disease