If the vaccination drive against coronavirus is not ramped up and COVID-19 appropriate behaviour is not maintained, there is a possibility of a third wave of the pandemic in 6-8 months, said M Vidyasagar, a scientist involved in the Sutra Model which uses mathematics to project the trajectory of COVID-19.
He, however, stressed the Sutra Model has not predicted any third wave and it is working on it.
The Indian Institutes of Technology-Hyderabad professor cited a paper by Italian researchers on infected people with decreasing antibodies, which give some sort of immunity, in six months.
"If the antibodies are lost, then there is a chance of immunity going down. In this case, vaccination has to be ramped up and COVID-19 appropriate behaviour must be practiced. If not then there is a possibility of a third wave in 6-8 months," Vidyasagar said.
"We are also adding the aspects of immunity and vaccination in our model for our future forecasts," he added.
According to a study by the San Raffaele hospital in Milan, antibodies against coronavirus remained in the blood of patients with COVID-19 for at least eight months after they were infected.
A recent sero-survey by the Institute of Genomics and Integrative Biology (IGIB) suggested that the neutralising antibodies declined significantly after five-six months, making people prone to reinfections.
The coronavirus cases in the country peaked in September 2020 and there was a nationwide decline of new cases starting in October.
"Using more stringent measures (more than 30 per cent inhibition of surrogate receptor-spike protein binding), the loss of neutralisation maybe even higher.
"We speculate that this may be related to recurrence of outbreaks in March 2021, after the peak in September 2020," the IGIB paper said on the second wave that started raging from late March and has claimed thousands of lives since then.
K Vijay Raghavan, Principal Scientific Adviser, had said on May 5 that as the virus mutates further, the third wave of COVID infection is inevitable and it is necessary to be prepared for new waves.
Two days later, he said there may not be the third wave of coronavirus in the country if strong measures are taken and effectively implemented at the state, district, and city level.
"If we take strong measures, the third wave may not happen in all places or indeed anywhere at all. It depends on how effectively guidance is implemented at the local level in the states, districts, and cities everywhere.
"The guidance about precautions, about surveillance, about containment, about treatment and about tests. This insidious asymptomatic transmission can be stopped if we follow the guidelines. This sounds difficult, it is difficult and we can and must do it," Vijay Raghavan had said in a press briefing.