JOHNSON & JOHNSON has asked US regulators to clear the world’s first single-dose coronavirus vaccine, an easier-to-use option that could boost scarce supplies.

Preliminary results from a massive study of 44,000 people in the US, Latin America and South Africa showed the jab was safe and offered strong protection against moderate to severe Covid-19.

It did not appear quite as strong as two-dose competitors made by Pfizer and Moderna.

Overall, the single-dose vaccine was 66% effective at preventing moderate to severe Covid-19 but it was 85% protective against the most serious symptoms — and starting 28 days after their shot, researchers found no one who got the vaccine needed hospitalisation or died.

Johnson & Johnson filed an application with the Food and Drug Administration (FDA) yesterday.

An FDA panel will meet later this month and pore over the results.

Dr Peter Marks, FDA’s vaccine chief, has cautioned against making comparisons before the evidence is all in.

“With so much need to get this pandemic under control, I think we can’t ignore any tool in the tool chest,” he told the American Medical Association last week.

“We will have to do our best to try to make sure that we find the populations that benefit the most from each of these vaccines and deploy them in a very thoughtful manner.”

J&J also is studying a two-dose version of its vaccine, but results will not be available for several more months.

It is likely to be several months before the J&J vaccine is available in Ireland. It is expected that the company won’t submit its vaccine to the European Medicines Agency for approval until March at the earliest.