A link between AstraZeneca's Covid-19 jabs and blood clots is plausible but unconfirmed, the World Health Organization's vaccine experts said Wednesday, stressing that reported occurrences were "very rare".
The statement came after the EU's EMA drug regulator said earlier in the day that blood clots should now be listed as a "very rare" side effect of the AstraZeneca coronavirus vaccine.
But the jab's benefits continue to outweigh the risks, it added.
The Covid-19 sub-committee of the WHO Global Advisory Committee on Vaccine Safety met on Wednesday to review the latest information from the EMA, British and other medicines regulators.
"Based on current information, a causal relationship between the vaccine and the occurrence of blood clots with low platelets is considered plausible but is not confirmed," the GACVS said.
"Specialised studies are needed to fully understand the potential relationship between vaccination and possible risk factors.
"Whilst concerning, the events under assessment are very rare, with low numbers reported among the almost 200 million individuals who have received the AstraZeneca Covid-19 vaccine around the world."
"We believe the benefit-risk balance is very much in favour of the vaccine," said the WHO in response to an AFP query. "Nothing has changed in our advice -– which is to keep vaccinating."
– Side effects 'common' –
It said that rare adverse effects had to be assessed against the risk of death from Covid-19 and the potential of vaccines to prevent coronavirus infections and reduce deaths.
Side effects within two or three days following vaccination "are expected and common", it noted.
"However, individuals who experience any severe symptoms… from around four to 20 days following vaccination, should seek urgent medical attention."
Those include shortness of breath, chest pain, leg swelling, persistent abdominal pain, neurological symptoms, such as severe and persistent headaches or blurred vision, and tiny blood spots under the skin beyond the injection site, the GACVS said.
The group suggested that a panel of clinical experts including haematologists should be convened for advice on clinical diagnosis and case management.
"The GACVS will meet again next week to review additional data and will be issuing further recommendations as relevant," it said.
– 'Risk-benefit' assessment –
The AstraZeneca jabs produced in South Korea and India, plus the Pfizer-BioNTech vaccine and that of Johnson and Johnson, are the only ones to have received WHO authorisation so far in the Covid-19 pandemic.
The AstraZeneca vaccine accounts for almost all of the doses being distributed around the world in the first wave of the Covax global vaccine-sharing facility.
Covax has now delivered 36 million doses of coronavirus vaccine to 86 countries and economies, the WHO said Tuesday.
The scheme aims to ensure poorer nations get enough doses to vaccinate at least 20 percent of their population by the end of the year.
Overall, more than 694 million doses of Covid-19 vaccines have been injected in at least 195 territories around the world, according to an AFP count.
The novel coronavirus has killed nearly 2.9 million people since the outbreak emerged in China in December 2019, according to a tally from official sources compiled by AFP. At least 132 million cases have been registered.
