The World Health Organization gave strong backing to the AstraZeneca COVID-19 jab on Friday, urging countries to maintain the roll-out after reviewing reports of blood clots.
WHO director-general Tedros Adhanom Ghebreyesus said there was "no question" over the benefits after the UN health agency's vaccine safety experts found no increase in clotting conditions linked to an AstraZeneca shot.
Several European countries resumed AstraZeneca vaccinations on Friday after the European Medicines Agency (EMA) likewise gave their green light on Thursday.
"We understand that people may have had concerns about the safety of the Oxford-AstraZeneca vaccine," Dr Tedros told a press conference.
"The question with any pharmaceutical or vaccine is whether the risk of taking it is greater or less than the risk of the disease it is meant to prevent or treat.
"There is no question: COVID-19 is a deadly disease and the Oxford-AstraZeneca vaccine can prevent it.
"The available data do not suggest any overall increase in clotting conditions following administration of the Oxford-AstraZeneca COVID-19 vaccine.
"We urge countries to continue using this important vaccine."
The WHO's Global Advisory Committee on Vaccine Safety (GACVS) met virtually on Tuesday and Friday this week.
It reviewed available information and data on thromboembolic events (blood clots) and thrombocytopenia (low platelets) after vaccination with an AstraZeneca COVID-19 shot.
The committee said the jab "continues to have a positive benefit-risk profile, with tremendous potential to prevent infections and reduce deaths across the world.
"The available data do not suggest any overall increase in clotting conditions such as deep venous thrombosis or pulmonary embolism."
Those two conditions "occur naturally and are not uncommon", and also occur as a result of COVID-19, the experts said.
"While very rare and unique thromboembolic events in combination with thrombocytopenia, such as cerebral venous sinus thrombosis (CVST), have also been reported following vaccination with the AstraZeneca COVID-19 vaccine in Europe, it is not certain that they have been caused by vaccination."
The EU's EMA regulators have reviewed 18 such cases out of more than 20 million AstraZeneca COVID-19 vaccinations in Europe, and "a causal relationship between these rare events has not been established at this time".
The AstraZeneca vaccine accounts for more than 90 per cent of the doses being distributed around the world in the first wave of the Covax global vaccine-sharing facility.
Just under 30 million doses have so far been distributed to 50 countries as part of the scheme, which aims to ensure poorer nations get enough doses to vaccinate at least 20 per cent of their population by the end of the year.
European countries resume shots
Worries that AstraZeneca's vaccine may cause blood clots have seen countries from Venezuela to Indonesia pause its use in recent days, besides European nations.
But Germany and Italy, among others, said they were using the jab again as of Friday after the EMA said it was "safe and effective".
Other European countries including the Netherlands, Spain and Portugal are also ending their suspension.
The WHO vaccine safety experts recommended that countries continue monitoring COVID-19 vaccine safety and report suspected adverse events.
The GACVS also agreed with the EMA's plans to further investigate and monitor for such events.
The committee said health care professionals and people being vaccinated should be told how to recognise the signs and symptoms of all serious adverse events after immunisation with COVID-19 jabs.