The Netherlands has become the latest country to halt use of the Oxford-AstraZeneca Covid vaccine over concerns about possible side effects.
The WHO and the European Medicines Agency (EMA) say there is no indication of a link between the vaccine and reports of blood clots.
Eight countries have so far fully suspended the AstraZeneca vaccinations.
The WHO told Reuters it was important that vaccination campaigns continued.
About 17 million people in the EU and the UK have received a dose of the vaccine, with fewer than 40 cases of blood clots reported as of last week, AstraZeneca said.
Experts say the number of blood clots reported after the vaccine were no more than those typically reported within the general population.
However, the Dutch government said its suspension, which will last until at least March 29, was a precaution.
Ireland, Denmark, Norway, Bulgaria and Iceland have paused inoculations with AstraZeneca vaccine, while the Democratic Republic of Congo and Indonesia have delayed the start of their AstraZeneca rollouts. Several European countries, including Italy and Austria, have suspended the use of certain batches of the drug as a precautionary measure.
Thailand announced that it would start using the vaccine on March 16, following a brief delay to the rollout over safety concerns.
The EMA – which is currently carrying out a review into incidents of blood clots – said the vaccine could continue to be administered.
In a statement, the Dutch government said it was acting out of precaution following reports from Denmark and Norway of possible serious side effects.
Dutch drug watchdog Pharmacovigilance Centre Lareb later said that 10 cases of possible adverse side effects had been reported in the Netherlands, according to Reuters.
“We can’t allow any doubts about the vaccine,” Health Minister Hugo de Jonge said.
“We have to make sure everything is right, so it is wise to pause for now.”
Speaking on an early morning talk show on March 15, Hugo de Jonge said he hoped the suspension would last “no longer than a couple of weeks”, adding: “We need vaccines to be able to put this nasty period behind us.”
The government’s decision will now cause delays in the Dutch vaccination program.
The authorities had pre-ordered 12 million doses of AstraZeneca, with nearly 300,000 shots scheduled in the next two weeks.
AstraZeneca said there was no evidence of an increased risk of clotting due to the vaccine.
It said that across the EU and UK there had been 15 events of deep-vein thrombosis (DVT) – a blood clot in a vein – and 22 events of pulmonary embolism – a blood clot that has entered the lungs – reported among those vaccinated.
AstraZeneca said these figures were “much lower than would be expected to occur naturally in a general population of this size and is similar across other licensed Covid-19 vaccines”.