WASHINGTON — Pharmaceuticals giant Johnson & Johnson (J&J) on Thursday (Feb 5) submitted an application for emergency authorisation of its Covid-19 vaccine with US health authorities, the company said.

The process could take several weeks, but if approved, the vaccine would be the third authorised in the United States, after those of Pfizer-BioNTech and Moderna.

J&J subsidiary Janssen Biotech "has submitted an application to the US Food and Drug Administration (FDA) requesting Emergency Use Authorization for its investigational single-dose Janssen Covid-19 vaccine candidate," a company statement read.

The new vaccine is highly anticipated because it has two big logistical advantages — it can be stored at refrigerator temperatures rather than in special freezers, significantly easing distribution; and it requires just one dose.

Following J&J's request, the FDA is expected to convene its advisory committee on vaccines, which will deliver its opinion after studying the data from clinical trials.

It will be responsible for determining whether the benefits of the vaccine outweigh the risks.

That step took about three weeks for the Pfizer-BioNTech and Moderna vaccines, but could be faster this time around.

The final green light will then be given, probably the next day.

J&J announced at the end of last week the first results of its clinical trials, carried out on nearly 44,000 people in eight countries.

The vaccine was overall 66 per cent effective, the company said. And it is 85 per cent effective in preventing severe forms of the disease.

But these results also raised a concern — the shot was more effective in the United States (72 per cent), than in South Africa (57 per cent), where a variant that had appeared in the country has now became dominant.

Experts see this as an indication that future variants of the virus could end up completely bypassing the immune defenses developed by the current vaccines.

They argue this is yet another reason to speed up vaccination campaigns, since the variants evolve from mutations that occur when the virus replicates.

"Viruses cannot mutate if they cannot replicate," said Dr Anthony Fauci, the highly respected US presidential adviser.

The J&J shot uses a common-cold causing adenovirus, modified so it can't replicate, as a "vector" to shuttle genetic instructions into human cells, telling them to create a protein of the coronavirus.

This trains the immune system to be ready for the live coronavirus.

The J&J vaccine uses double-stranded DNA molecules to deliver its genetic instructions, which are hardier than the single-stranded RNA molecules used in Moderna and Pfizer vaccines, and eases the cold storage requirements.

The "viral vector" method is also employed by the AstraZeneca and Sputnik vaccines. AFP