The World Health Organization on Tuesday approved a Covid vaccine made by US pharma giant Novavax for emergency use, after the European Union medicines regulator gave it the green light.
The European Medicines Agency had assessed and approved Nuvaxovid on Monday.
The jab uses a traditional technology involving proteins found on coronavirus spike proteins that trigger an immune response.
It is a tried and tested approach, used for decades to vaccinate people against diseases including hepatitis B and whooping cough.
A so-called emergency use listing (EUL) by the WHO paves the way for countries worldwide to quickly approve and import a vaccine for distribution.
It also opens the door for them to enter the Covax global vaccine-sharing scheme, set up to provide equitable access to doses around the world and particularly in poorer countries.
The two-shot Nuvaxovid jab is the 10th Covid vaccine issued an EUL by the UN health agency.
WHO said Nuvaxovid was around 90-percent effective at reducing symptomatic cases of Covid-19 in two major clinical studies, one in Britain and the other in the United States and Mexico, involving more than 45,000 people.
In a separate document, WHO's Strategic Advisory Group of Experts on Immunisation recommended the new vaccine for use in people over the age of 18, with an interval of three to four weeks between the two doses.
"The vaccine should not be administered with an interval of less than three weeks," it warned.
It can be kept at refrigerated temperatures between 2 and 8 degrees Celsius, giving it a logistical advantage in difficult-to-access regions over the mRNA vaccines, which must be stored at ultra-low temperatures.
Among the Covid vaccines already handed a WHO EUL is the Covovax shot, a version of Novavax's vaccine made by the Serum Institute of India under licence from the US-based company.
It was authorised on December 17.
Also figuring on the list are the mRNA vaccines produced by BioNTech/Pfizer and Moderna, Johnson&Johnson, AstraZeneca (which is counted twice for the versions made in Europe and in India), the Indian-made Covaxin and Chinese-made Sinopharm and Sinovac.
The WHO also recently resumed evaluating the Russian-made Sputnik V vaccine against Covid-19, after several months in limbo, as it waited for additional data.
Rogerio Gaspar, head of WHO's regulation and prequalification department, said Monday that the UN health agency would begin assessing the quality of the data received next month and aimed to carry out inspections on-site in February.
He told reporters he could provide "no date on approval because the approval will depends really ... on the quality of the information."
Neither US nor EU medicines watchdogs have so far granted authorisation for Sputnik V, which has been used in Russia and some other countries since late 2020.