NEW DELHI: The Indian Council of Medical Research (ICMR) is set to undertake a crucial research project to assess the immunological response to Covid-19 amid concerns that antibodies against SARS CoV 2 may not be long-lasting. Through the exercise, scientists will also try to examine at what level of infection prevalence can herd immunity be expected in any area.
For the project, ICMR scientists will collaborate with researchers at the AIIMS-Delhi where a cohort of recovered Covid-19 patients will be studied over a period of time to assess their antibody levels and its role in coming months. Sources told this newspaper that an ICMR expert group on surveillance and epidemiology has approved the proposal and a protocol for the study is now being designed.
“We need to examine whether the population, at least, in high exposure areas, is any closer to herd immunity which will depend on the type of antibodies produced,” a source at the ICMR said.“For example, are they neutralising antibodies? And how long will they last or how quickly might they wane?... “We could do these studies on people at least in containment zones with high exposure levels,” he added.
Experts explained that immune memory appears critical for both herd immunity — whether from natural infections or the vaccines.
“So far, what we have understood is that while antibodies that Covid-19 pathogen triggers do not last long, it also spurs T-Cell memory response which is a good thing for both herd immunity and development of vaccines,” said virologist Dr J Muliyil. A recent and first of its kind longitudinal study — in which subjects are observed over a period of time without any intervention - immune response of over 90 patients and healthcare workers who had recovered from the disease — was published from the UK.
It was seen that antibodies that can destroy the virus peaked about three weeks after the onset of symptoms and then dropped rather swiftly. The blood test of the recovered patients also revealed that while 60 per cent of people showed very potent antibody response at the height of their battle with the virus, only 17 per cent retained the same potency three months later. Also, antibody levels declined as much as 23-fold over the period and in some cases, there were no detectable antibodies at all.