In case of the 'pessimistic' scenario, the third wave could see cases rise up between 1,50,000 to 2,00,000 in the country
New Delhi: The third wave of coronavirus could hit the peak between October-November if Covid appropriate behaviour is not followed, but may see half the daily cases recorded during the second surge, according to a scientist of a government panel tasked with modelling of COVID-19 cases.
He, however, said the third wave could spread faster if any new virulent variant emerges.
Manindra Agarwal, involved in the Sutra Model' or the mathematical projection of trajectory of COVID-19, also said the model has three scenarios--optimistic, intermediate and pessimistic--for the prediction of the third wave.
The Department of Science and Technology had last year formed the panel to forecast the surge of coronavirus cases using mathematical models.
The panel had also received flak for not predicting the exact nature of the second wave of Covid.
Agarwal, who is part of the three-member panel, said loss of immunity, effects of vaccination and possibility of a more virulent variant, have been factored while predicting the third wave, something which was not done during modelling the second wave.
We have created three scenarios. One is optimistic' one. In this, we assume that life goes back to normal by August, and there is no new mutant. Second is intermediate' one. In this, we assume that vaccination is 20 per cent less effective in addition to optimistic scenario assumptions.
Third is pessimistic' one. This has one assumption different from intermediate one: a new, 25 per cent more infectious mutant spreads in August (it is not delta+, which is not more infectious than delta), he said in a series of tweets.
According to the graph shared by Agarwal, the second wave is likely to plateau by mid-August, and the third wave could reach its peak between October and November.
In case of the pessimistic' scenario, the third wave could see cases rise up between 1,50,000 to 2,00,000 in the country, the scientist noted.
The figure is less than half of what was recorded when the deadly second wave had hit its peak in the first half of May, flooding hospitals with patients and claiming thousands of lives daily.
On May 7, India had recorded 4,14,188 COVID-19 cases.
If a new mutant comes, the third wave could spread rapidly, but it will be half of what the second wave was. Delta variant is infecting people who were infected with a different variant. So this has been taken into consideration, Agarwal said.
He said as vaccination progresses, the possibility of a third or fourth wave will be less.
In case of an optimistic' scenario, the daily cases could be in the range of 50,000 to 1,00,000. In case of the intermediate scenario (if it is assumed that vaccination is 20 per cent less effective, in addition to optimistic scenario assumptions), the cases could be in the range of 50,000 to 1,00,000, but more than the optimistic scenario, the panel member noted.
M Vidyasagar, scientist at IIT-Hyderabad, who is also involved in modelling of Covid cases, said hospitalisation could be less during the third wave.
He cited the example of the UK where in January more than 60,000 cases were reported with daily deaths touching 1,200. However, during the fourth wave, the number dropped to 21,000 cases and just 14 deaths.
Vaccination played a major role in bringing down the cases that needed hospitalisation in the UK. This has been factored while coming out with the three scenarios, Vidyasagar told PTI.
The government has been emphasising on vaccination as the fear of the third wave looms.
Agarwal also explained the reasons behind the delay in coming out with an analysis for the third wave.
It took us a while to do the analysis for three reasons. First, loss of immunity in recovered population. Second, vaccination induced immunity. Each of these two (factors) need to be estimated for future.
And third, how to incorporate these two factors in the Sutra model. Fortunately, it turned out that both can be incorporated by suitably changing contact rate and reach parameters. So that takes care of the third factor. The first two factors required detailed analysis, he tweeted.
Contact rate' is how fast the infection spreads and reach parameter' is the percentage of population the pandemic is active in.
Agarwal added that his team went through studies done in the past on loss of immunity while making the Sutra Model.
Similarly, we also looked at the projected vaccination rate over the next few months, including the effects of vaccine-hesitancy, and arrived at month-wise estimates for vaccination, he said.