NEW DELHI: Did lockdown help in controlling the Covid-19 spread in India? An analysis shows early lockdowns imposed when less than 1 per cent of the population has been infected are totally ineffective for flattening the curve and cannot prevent the return of the epidemic when the lockdown is lifted.
Results from a mathematical model by two retired senior scientists from CSIR — National Institute for Interdisciplinary Science and Technology (NIIST) shows that the curve starts climbing soon after lifting the lockdown and reaches a peak of the same height as the no-lockdown curve and more than the duration of the lockdown, it is the point of imposition of the lockdown that effectively flattens the curve.
How to Flatten the post-lockdown epidemic trajectory by Ajit Haridas and Roschen Sasikumar says the post-lockdown trajectory can be flattened only if the lockdown is imposed after about 10 per cent of the population has recovered after infection.
“Lockdowns are effective in maintaining the flattening of the curve after the lockdown period only if the lockdown is imposed after building up sufficient fraction of immune population. Any practical solution must work around the fact that the earlier the lockdown is imposed, the higher will be the post-lockdown resurgence,” said the pre-print analysis.
According to the analysis, from Day 1 to Day 70, the fraction of infected cases rises only to 1 per cent of the population, but from Day 70, the fraction increases rapidly to a peak of nearly 22.5 per cent of the population in 30 days and then falls to 1 per cent in another 40 days.
“It can be seen that the shape of the curves during mild and strong lockdowns are identical to the no-lockdown curve except for a delay in the occurrence of the peak. The same result is obtained whether the lockdown is for 20,40,60,80 or 100 days,” it added.
However, strong lockdown imposed on Day 80 reduces the peak from 22.5 per cent to 19.3 per cent and mild lockdown results in a lower post-lockdown peak of 18.6 per cent. Locking down on Day 90 ensures that peak always stays below 10 per cent in the case of strong lockdown and below 15 per cent when the lockdown is mild.