Herd immunity

The findings of seroprevalence surveys have raised hopes that herd immunity to Covid-19 may not be a distant dream, even as the total number of cases in India is nearing the 30-lakh mark and around 55,000 deaths have been reported so far. Antibodies against the coronavirus infection have been found in over 28 per cent of the people in Delhi, indicating that they have already got infected and recovered too. In Punjab’s containment zones, 27.7 per cent of the population has been found positive for Covid-19 antibodies, with Amritsar (40 per cent) topping the list. In Pune, the corresponding figure is as high as over 50 per cent.

There is, however, lack of unanimity among scientists worldwide about the herd immunity threshold. A section of them estimates that at least 70 per cent of the population must have antibodies to prevent spread of the disease, while some others say that protection is possible even if half the population becomes immune. Moreover, the jury is still out on whether having antibodies against the virus that causes Covid-19 can protect someone from getting infected again, and, if that is the case, how long this protection might last. The World Health Organisation (WHO) has stated that the focus should be on developing an effective vaccine rather than waiting indefinitely for herd immunity.

The surveys have reignited the debate on the efficacy of the nationwide lockdown that remained in force for over two months and impacted millions of lives as well as livelihoods. Did the stringent restrictions last too long and merely delay the inevitable? The unlocking, as expected, has led to a sharp spike in cases. Rattled, several states have reimposed the lockdown. The kneejerk reaction could prove to be ineffectual, if not counterproductive. In a study on the prevalence of Covid-19 in Spain, published in The Lancet last month, researchers concluded that ‘herd immunity could not be achieved without accepting the collateral damage of many deaths… and overburdening of health systems.’ Even as vigorous testing and tracing should continue along with vaccine research, Central and state governments should focus on the rebuilding of the economy.