Third wave of Covid-19 seems unlikely to severe as the second: ICMR study

If a third wave of Covid-19 occurs, then it is unlikely to be as severe as the second wave, considering the extent of spread of infections which has already befalled in the country, as per a study.

Based on mathematical modelling analysis published in the Indian Journal of Medical Research (IJMR), the study emphasizes that the arrival of the third wave of the Covid-19 could be substantially eased by the extension of vaccination.

“Any third wave seems unlikely to be as severe as the second wave. Rapid scale-up of vaccination efforts could play an important role in mitigating these and future waves of the disease,” the authors stated.

The study further using a conceptual model of SARS-CoV-2 transmission for the third wave examined four potential mechanisms. Firstly the decreasing immunity restores formerly exposed individuals to a susceptible state, emergence of a new viral strain that is capable of escaping immunity to formerly circulating variants, emergence of a new variant that is more transmissible than the already circulating strains and reopening of the present lockdowns give new opportunities for transmission.

Contemplating the four hypotheses for the arrival of a third wave, the study stated that the infection-induced immunity may decline over time, allowing re-infection of those formerly exposed, even if the moving virus remains unchanged.

Considering the hypothesis of an arrival of a full immune escape strain, the study added that even if immunity remains lifelong, it is likely possible for a new variant to arrive, which is capable of escaping the immunity induced by the formerly circulating strains.

The findings emphasize that immune-mediated mechanisms (waning immunity, or viral evolution for immune escape) are not likely to propel a severe third wave of Covid-19 if acting on their own, except those mechanisms lead to a complete loss of protection among those already exposed, the study said.

Likewise, a new and more transmissible variant would have to surpass a high threshold (R0 >4.5) to cause a third wave of the pandemic on its own. The plausible mechanisms for a third wave, however include a new variant that is more transmissible and simultaneously capable of escaping prior immunity, and lockdowns that are highly effective in curbing transmission and later released, it noted.

“In both cases, any third wave seems unlikely to be as severe as the second wave. Rapid scale-up of vaccination efforts could play an important role in mitigating these and future waves of the disease,” the study stated.

The study demonstrates plausible mechanisms by which a substantial third wave could emegre, while also explaining that it is unlikely for any such resumption to be as substantial as the second wave. However, model projections are subject to several uncertainties, and it is important to scale up vaccination coverage to decrease against any possibility, it said.

Precautionary planning for any probable future wave will help by drawing upon the estimated numbers based on the current modelling exercise the study further noted.

(Inputs from PTI)

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