The "herd immunity" strategy may have worked against the H1N1 influenza pandemic a decade ago, but the coronavirus that causes Covid-19 is more infectious and severe, warned Associate Professor Alex Cook.

It is not clear that such a strategy against Covid-19 is working, he said, adding that many countries that had initially adopted it have since abandoned the idea. Britain is one such example, he added.

The approach involves allowing the population to get infected and naturally build up immunity to a virus.

Most countries are now aligned with the World Health Organisation's advice on reducing the number of cases as much as possible, Prof Cook said.

Sweden, one of the few countries using an alternative approach that does not include strict lockdowns, has more than 27,000 confirmed cases of Covid-19. It has also reported over 3,400 deaths, which is several times more than in neighbouring Scandinavian countries.

The Swedish authorities have denied that their strategy was based on the overall goal of herd immunity.

Nonetheless, Prof Cook said he was glad Singapore is not adopting the same strategy.

"I hope Sweden is successful, but I think they may potentially be a role model for what not to do during a pandemic."