The plan to roll out Merck & Co's promising antiviral pill to treat Covid-19 risks repeating the inequities of vaccine distribution, potentially leaving the nations with the greatest need once again at the back of the line, international health groups say, according to Reuters.

Merck on Oct 11 applied for US emergency clearance of the first pill for Covid-19 after it cut hospitalisations and deaths by 50 per cent in a large clinical trial. The medicine, made with Ridgeback Biotherapeutics, could gain authorisation as soon as December.

The US drugmaker has taken the unusual pandemic step of licensing several generics of its antiviral molnupiravir before its branded version was even authorised for marketing.

But international health officials said even that is not enough for the medicine to reach many in low- and middle-income countries in large enough numbers, while noting shortcomings and red tape among global organisations that could further slow distribution.