‘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 non-peer reviewed international publication medRxiv on November 15 reveals that the vaccine provides a T-Cell response in the human body, helping it to fight the COVID-19 virus better.

A 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 study.

However, as the study has taken into account a small number of beneficiaries, health experts say, a clearer picture of T-Cells 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 long-term efficacy of the vaccine.

Dr Wiqar Shaikh, professor of Medicine, Grant Medical College and JJ Group of Hospitals said that in two earlier articles, mid-day had highlighted the need to study the T-Cell (cell-mediated) immune response of the human body following administration of COVID-19 vaccines. He added that it was particularly needed for Covaxin to demonstrate to the world that a COVID-19 vaccine researched and manufactured in India possessed all-round and robust efficacy.

He further said, "In 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 T-Cell immunity becomes the body's sole weapon. This is the job of two types of T-Cells - the Natural Killer (NK) cells and the Cytotoxic cells." Dr. Shaikh added, "The 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 T-Cells in 85 per cent of the beneficiaries who have been studied. Both antibodies and T-Cell 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 T-Cell response, particularly against COVID-19 variants. This puts Covaxin on a high pedestal amongst all the COVID vaccines."

He 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 non-peer reviewed journal.

Speaking to mid-day, Dr Subhash Hira, professor of Global Health at the University of Washington-Seattle, and an invited expert to several WHO COVID review forums, said, "It is a small sample study of 71 volunteers, who took two doses of Covaxin, and a separate cohort of 73 non-vaccinated individuals who got infected with mild COVID-19 and tested positive. Both groups were followed for six months to compare safety and immunogenicity of vaccine-induced infection and natural COVID-19 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 three-month interim follow-up of vaccines."

"The 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 large-sized study is required wherein vaccine volunteers are followed up after every quarter for 18-24 months or even longer to establish neutralising antibody levels, increase in CD4 cell count after Covaxin injections, and role of memory T-cells 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 follow-up period of 18-24 months. This is then quantified in the laboratory," added Dr. Hira.

He further said, "Bharat Biotech is on record testing diluted forms of Covaxin for children between 2-15 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 cell-mediated immunity by memory T-Cells for a lifetime. These are exciting times for innovation-driven companies like Bharat Biotech to take the global leadership and expand its pool of global scientists."