New Delhi- A third wave of Covid – if it occurs – is unlikely to be as severe as the second wave given the extent of spread of coronavirus infections that has already taken place in the country, according to a study.
The study, based on mathematical modelling analysis published in the Indian Journal of Medical Research (IJMR), highlights that the emergence of a third wave of coronavirus could be substantially mitigated by the expansion of vaccination.
Presenting a vaccine ramp-up scenario where 40 per cent of the population has received two doses within three months of the second wave peak, and further that the effect of vaccination is (conservatively) to reduce severity of infection by 60 per cent, the study said it illustrates how vaccination could substantially reduce the overall burden during the possible third wave.
‘Plausibility of a third wave of Covid in India: A mathematical modelling-based analysis’ has been authored by Sandip Mandal, Balram Bhargava and Samiran Panda from the Indian Council of Medical Research (ICMR), and Nimalan Arinaminpathy from the Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College, London, UK.
Using a deterministic, compartmental model of SARS-CoV-2 transmission, four potential mechanisms – waning immunity restores previously exposed individuals to a susceptible state, emergence of a new viral variant that is capable of escaping immunity to previously circulating strains, emergence of a new viral variant that is more transmissible than the previously circulating strains and release of current lockdowns affording fresh opportunities for transmission – for a third wave were examined, the study said.
Considering the four hypotheses for the emergence of a third wave, the study said infection-induced immunity may decay over time, permitting re-infection of those previously exposed, even if the circulating virus remains unchanged.
Previous works have shown how partially waning immunity could cause future waves of SARS-CoV-2 to be more benign, but the focus here was on the possibility of a third wave that may cause substantial public health burden, the study noted.
Therefore, a scenario where waning immunity results in a full loss of protection, rendering immune individuals susceptible again was considered, and a range of scenarios for the rate of waning were examined, it added.
Considering the hypothesis of an emergence of a full immune escape variant, the study said even if immunity remains life-long, it is theoretically possible for a new variant to emerge that is capable of escaping the immunity induced by the previously circulating strains.
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