The purpose of a lockdown is to retard the speed of virus transmission. Therefore, it is most beneficial when transmission speed or momentum is accelerating, but the benefit risk ratio reverses as the momentum begins to decelerate.
The epidemic curve ascends when one infected person infects more than one susceptible person — that’s when infection’s effective reproduction number (Re) >1. The curve descends when one infected person infects less than one other person (Re
Lockdown during the rapid phase of increasing transmission helps to minimise Re and reduce it to less than 1. When Re
Presented in graphic form, the data of new cases, deaths, and cumulative active cases shows the ascent, peak, and decline visually. Numerical peaks of these parameters are based on the counted numbers. ‘Momentum’ and ‘mortality acceleration’ are innovative mathematical derivations to analyse how the epidemic is moving across the whole country, states and districts.
It’s essential to analyse every state and district separately for actions like graded relaxation of local lockdowns. Health officials can use the free web-based analytical tool at tiny.cc/covid-momentum to quickly analyse state- and district-level dynamics of the second wave for timely interventions.
Comprehensive data
We have illustrated national- and state-level epidemic profiles with sets of five graphs for each showing momentum, daily new cases, active cases, mortality acceleration and daily deaths, with dates of peaks for places that have peaked. The peaks for states appear in the following sequential order: momentum peak, numerical peak, mortality acceleration peak, active cases peak, and numerical mortality peak.
Peaks for the whole country represent a statistical average of all states, and state-wise peaks represent the statistical average of all districts.
The data shows the second wave started and peaked in different states and districts at different times. It is apparent that all states have reached both momentum peak and numerical peak of daily new cases. Now, momentum and daily numbers are declining in all states. But as of June 7, active cases, mortality acceleration and numerical deaths had not peaked in the seven Northeastern states, Tamil Nadu, Odisha and Lakshadweep.
When to unlock
Any state that has reached all five peaks ought to call off the state-wide lockdown immediately. There is no justification to prolong people’s agony. In fact, all states where momentum and numerical new cases have peaked can also unlock in a careful and gradual district-wise manner, while preparing to tackle the imminent peaks of active cases, mortality acceleration and numerical deaths.
We distinguish the two groups mainly to point out that states yet to reach mortality peak must focus efforts on making available sufficient oxygen, essential drugs, hospital beds, and ICU beds.
Even after unlocking, all states must focus on applying “social vaccine” besides the “biological vaccine”. States with declining mortality and surplus essential items like oxygen concentrators and drugs should consider sharing these with needy neighbours.
Social vaccine consists of information-education-communication plus behaviour change education for Covidappropriate mask-wearing and physical distancing — which can be relaxed to arm’s length if all are wearing masks — avoiding crowds, good ventilation of all closed environments, cough-sneeze etiquette and hand hygiene.
Actually, lockdown should be resorted to only after the full use of the social vaccine. The value of the social vaccine was a lesson India had taught the world during the HIV/AIDS pandemic. We failed to learn from history and suffered the consequences during the Covid pandemic. If we use social and biological vaccines effectively and achieve wide coverage quickly, we can prevent a potential third wave.
