The European Medicines Agency has said that it is set to decide whether to authorise Johnson & Johnson's single-shot coronavirus vaccine for the 27-nation EU on 11 March.

"EMA's human medicines committee expected to give its recommendation for Covid-19 vaccine from Janssen (J&J's European subsidiary) on 11 March," at a special meeting, the Amsterdam-based regulator said on Twitter.

Meanwhile, US President Joe Biden plans to announce an arrangement for pharma giant Merck to produce Johnson & Johnson's single-dose Covid-19 vaccine to boost supply, a senior Biden administration said today.

The official confirmed a Washington Post report on the unusual agreement, which is designed to significantly boost vaccine supply as the Biden administration seeks to tame a coronavirus outbreak that has claimed more than 500,000 American lives.

The J&J vaccine is the third to receive US regulatory approval for emergency use, but the first that requires a single shot as opposed to two jabs.

Merck will dedicate two facilities in the United States to the J&J vaccine build-out, one to manufacture the vaccine and the other to conclude the production process by putting the substance in vials and packing it for shipment, the Post reported.

Neither Merck nor J&J immediately responded to a request for comment.

Earlier, the European Commission said that it was considering emergency approvals for Covid-19 vaccines as a faster alternative to more rigorous conditional marketing authorisations, which have been used so far.

The move would mark a big shift in approach to vaccine approvals, as it would entail using a procedure that the EU had considered dangerous and that before the Covid-19 pandemic had been reserved for exceptional authorisation at national level of drugs for terminally ill patients, including cancer treatments.

The potential change comes as the EU executive and the bloc's drug regulator come under increasing pressure for what some consider slow vaccine approvals, which have contributed to a slower rollout of Covid-19 shots in the 27-nation union, compared to the United States and former EU member Britain.

"We are ready to reflect with the member states on all possible avenues to indeed accelerate the approval of the vaccines," an EU Commission spokesman told a news conference.

One option could be "an emergency authorisation of vaccines at EU level with shared liability among member states", the spokesman said, adding that work on this could start very quickly if EU governments supported the idea.

It was not clear whether an EU-wide emergency authorisation procedure, if agreed upon, would entail the same conditions as emergency approvals granted at national level, the commission spokesman said.

The European Medicines Agency (EMA) cannot currently issue emergency approvals but in exceptional circumstances has recommended the compassionate use of drugs before marketing authorisation.

This procedure was used in April to initially authorise doctors to use Gilead's antiviral drug remdesivir as a treatment against Covid-19. The drug was later given conditional approval by EMA.

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National emergency approvals are allowed under EU laws, but they force countries to take full responsibility if something goes wrong with a vaccine, whereas under the more rigorous marketing authorisation, pharmaceutical companies remain liable for their vaccines.

The EU Commission had said that national emergency authorisations should not be used for Covid-19 vaccines, because faster approvals could reduce regulators' ability to check efficacy and safety data.

This could also boost vaccine hesitancy, which is already high in some countries, EU officials had said.

One senior EU official said the emergency procedure had so far usually been used at national level for terminally ill patients and the EU had instead chosen the lengthier conditional marketing authorisation because with vaccines "we inject healthy people" and the risk was disproportionate.

The change of tack would come after Eastern European countries, including Hungary, Slovakia and the Czech Republic, approved Russian and Chinese vaccines with national emergency procedures.

Britain has also used the emergency procedure to approve Covid-19 vaccines.