NEW DELHI: A mathematical projection model by Covid-19-Sutra -- jointly developed by researchers from Indian Institutes of Technology in Kanpur and Hyderabad -- has predicted that a major third wave of the pandemic in India is highly unlikely.
In the worst-case scenario, the model led by IIT Kanpur professor Manindra Agrawal, has said that there could be up to 2 lakh daily new infections between October and November this year, assuming that 50% of infected persons lose immunity after three months and the remaining stay immune.
Other assumptions for this scenario is that 25% become immune one month after first vaccine shot, another 25% one month after second shot and a fresh mutant arrives by August-end which will raise the contact rate to 0.5.
In the intermediate scenario, as per the projection, there could be up to 75,000 daily Covid-19 cases, assuming that 50% infected persons lose immunity after three months while remaining stay immune.
This scenario also assumes that 25% become immune one month after the first vaccine shot, another 25% one month after the second shot and a new mutant comes up leading to the maximum contact rate of 0.4.
On the other hand, in the best-case scenario, the level of daily new cases will stay as low as they are now -- at under 50,000 -- and this assumes that 40% of infected persons lose immunity after three months and 30% become immune one month after first vaccine shot, and another 30% one month after second shot.
For this possible scenario, no new mutant will have to emerge and the contact rate will need to stay at 0.4.
The researchers assumed that the next wave will not start before August this year as a new mutant takes at least a couple of months to spread over a large region and people are just coming out of a bad second wave, and are expected to be cautious for at least another couple of months.
The researchers also projected that by November this year, only 75% of the adult population may get vaccinated due to vaccine hesitancy.
Their work also highlighted that while infected persons develop immunity; however, for some of them it does not last long and evidence from last year suggests that between 5-20% of infected people lose immunity within eight months.
The researchers noted that with the new delta variant of SARS CoV 2 spreading in the last few months, there are indications that immunity loss is higher and some, as yet informal, estimates put it at nearly 40.
The more recent delta plus variant is believed to cause even higher immunity loss and the researchers associated with the project estimated it to be around 50%.
However, they stressed that the two vaccines presently used in India provide good immunity against the virus and even though the vaccine efficacy may be lowered against delta and delta plus variants, vaccination may be a key tool to fight the pandemic.