Researchers have been puzzled about why while the COVID-19 pandemic ravages China, Europe and now North America, low-income countries in South Asia have so far recorded fewer cases.

Public health experts say one reason is that the poorer countries just do not have enough kits to screen populations at risk for the virus. But others maintain that even there were a lot of infected people around, the coronavirus is not spreading in the subcontinent as aggressively as elsewhere.

There are many theories floating around to explain this, including the ‘hygiene hypothesis’ which seems to show that South Asians have developed a resistance to new viruses because the environment is not as sterile as in industrialised countries. Other scientists have speculated that countries with a high incidence of malaria seem to be relatively less affected, and have even proposed chloroquine as a cure.

One theory that appears more plausible is that people in countries that administer the anti-tuberculosis vaccine BCG (Bacillus Calmette-Guerin) seem to be less susceptible to COVID-19. Even before this pandemic, there had been epidemiological studies that indicated higher immune levels in people with BCG against communicable diseases, including viral infections.

Could Nepal’s surprisingly low caseload of novel coronavirus be attributed to the BCG vaccine which has been widely used in the population for the past five decades? The BCG vaccine campaign started in Nepal in 1979 under Expanded Program on Immunisation of the World Health Organization (WHO), and since then millions of Nepalis have been inoculated with it.

The rates of morbidity and mortality from COVID-19 vary greatly in different parts of the world, and scientists have been trying to understand why. For example countries like Italy, the Netherlands and the United States that never had a comprehensive BCG vaccination program appear to be disproportionately imapcted. There are now tests going on in several laboratories in Europe to see if this is indeed true.