The researchers who have estimated the potential benefits of face masks in the US population at 70 to 90 per cent vaccination coverage said their results may apply to other countries, providing estimates for how long facemasks remain cost-effective.

Multiple earlier studies have shown that face masks can help curb the spread of Covid-19, but the economic value of face masks at different vaccination coverage levels has been unclear. About 65 per cent of the US population and nearly 60 per cent of India’s population, including over 82 per cent of its adults, had been fully vaccinated up to March 6.

Health authorities in India have urged the public to continue using face masks in public spaces and adopt Covid-19 appropriate precautions despite a steady shrinking epidemic. India recorded 3,993 new infections on Tuesday, the lowest daily count since May 2020.

The new computational study has estimated that if the US were to achieve 90 per cent vaccination coverage by May 1 2022, maintaining face masks would avert 6.29 million cases, 136,700 hospital admissions, and 16,000 deaths.

At 80 per cent coverage by May 1 2022, continued face mask use would avert 7.66 million cases, 174,900 hospital admissions, and 20,500 deaths, according to the calculations. The findings were published in The Lancet Public Health, a peer-reviewed journal, on Tuesday.

The computations suggest it was cost effective to maintain face mask use between two to 10 weeks after achieving population vaccination targets, when the cost of mask-wearing per person was less than US$1.25 per person per day.

The findings assume relevance at a time the latest omicron-driven surge has fallen and people are questioning how long the current guidelines for continued face mask use will remain applicable.

“Our findings offer some light at the end of the tunnel, suggesting that face mask use doesn’t have to continue forever, but that it remains an important tool to stop the spread of Covid-19 as we enter the next phase of the pandemic,” said Peter Hotez, paediatrician and virologist at the Baylor College of Medicine in the US, the study’s co-author.

Although the omicron-driven surge is falling worldwide, scientists say the continued circulation of SARS-CoV-2, the virus that causes Covid-19, carries the risk of genetic mutations leading to the emergence of new variants.

“Virus transmission does not stop (when) population vaccination targets are met, but maintaining mask use for a few weeks after reaching the targets delivers economic and health benefits,” said Maria Elena Bottazzi, another co-author at the Baylor College of Medicine.