The US Food and Drug Administration greenlit Johnson & Johnson's one-dose coronavirus vaccine for emergency use on Saturday evening.

The authorization was approved a day after an independent panel of experts gave their recommendation for the jab. It is the third vaccine to be approved in the US, following in the footsteps of the BioNTech-Pfizer and Moderna vaccines.

"The authorization of this vaccine expands the availability of vaccines, the best medical prevention method for Covid-19, to help us in the fight against this pandemic, which has claimed over half a million lives in the United States," said acting Food and Drug Administration director Janet Woodcock.

US President Joe Biden welcomed the news, calling it an "encouraging development," but warned people that "we cannot let our guard down now or assume that victory is inevitable."

"Things are still likely to get worse again as new variants spread," the president said.

Protects from serious illness

The New Jersey-based company is planning to deliver some 20 million doses to the country by the end of March with a total of 100 million doses planned for the first half of the year.

The Johnson & Johnson vaccine is simpler than the alternatives as it only requires one shot. Global clinical trials showed that it was 66% effective at preventing various COVID-19 variants and 85% effective at protecting people from developing severe infections.

The Centers for Disease Control reported on Saturday that around 48.4 million people in the US have received at least one shot of a coronavirus vaccine so far. Nearly 512,000 people have died of COVID-19 in the United States, more than any other nation, though Belgium has suffered the most deaths per capita. 

Johnson & Johnson is also seeking authorization for emergency use of its vaccine in Europe and from the World Health Organization. Worldwide, the company aims to produce about 1 billion doses globally by the end of the year. On Thursday, Bahrain became the first to clear its use.

"The more vaccines that have high efficacy that we can get into play, the better," Dr. Anthony Fauci, the top US infectious disease expert, said ahead of the FDA's ruling.

How does the Johnson & Johnson vaccine differ from the alternatives?

Whereas the BioNTech-Pfizer and Moderna vaccines are based on RNA technology, the Johnson & Johnson vaccine is a more traditional approach to inoculation — it uses a common cold virus carrying coronavirus proteins to trigger an immune response.

The doses also remain stable at normal refrigerator temperatures for at least three months while Moderna must be kept frozen and the BioNTech-Pfizer vaccine has to be delivered at ultra-low temperatures, causing logistical problems for distribution to more rural areas.

The effectiveness of the BioNTech-Pfizer and Moderna vaccines in protecting against the virus were around 95% in US-based trials. The lower effectiveness of the Johnson & Johnson vaccine has been partially put down to the fact that trials were conducted after more aggressive variants of the disease became more prevalent.

ab/sms (AP, AFP, Reuters, dpa)