The stumble is the latest misstep for AstraZeneca, which had announced that the vaccine was found to be 79 per cent effective in preventing COVID-19 in the US clinical trial of more than 30,000 volunteers.
The results were reported in a brief press release.
Anthony Fauci: Mr Fauci admitted that it was unfortunate that some of the information in the initial AstraZeneca vaccine was outdated as this has sparked further concern.
In Norway, a top official warned on Monday it might not be able to resume its use of the AstraZeneca vaccine because so many people were rejecting it. Our Privacy Notice explains more about how we use your data, and your rights.
"It was not necessary-if you look at it, the data really are quite good, but when they put it into the press release it wasn't completely accurate", he added. Such reporting milestones are standard in clinical trials.
The vaccine has had a rocky rollout, especially in Europe, where it's now at the center of a supply showdown between the European Union and the U.K. Concerns about blood clots just days ago prompted around a dozen countries to suspend immunizations, though most have since resumed using the vaccine.
President Moon Jae-in is receiving his first dose of the AstraZeneca vaccine at a public health center in Jongno District, central Seoul, on Tuesday.
Deliveries of coronavirus vaccines are ramping up in Canada, with some 2 million doses of the Pfizer Inc and Moderna Inc vaccines coming in this week. Regulators there said last week that the shot was "safe and effective," having conducted a review after a small number of people who had recently been inoculated developed blood clots and abnormal bleeding.
A delay in the vaccine's authorization in the United States is unlikely to slow that country's immunization campaign; the USA expects to have enough doses of three other vaccines for its entire population by the end of May. Something about the AstraZeneca vaccine seems to trigger a similar syndrome, the researchers say, which they dubbed vaccine-induced prothrombotic immune thrombocytopenia (VIPIT). But Tuesday's statement from the U.S. National Institute of Allergy and Infectious Diseases (NIAID) cast doubt on whether the U.S. would imminently green light the jab.
But public confidence in America and Europe was dented by early questions over trial data and then by reports of unusual blood clots among those who had taken it. In the summer, the USA suspended its trial for over two months after health regulators were reportedly concerned by the company's lack of transparency in reporting isolated cases of neurological injury that were possibly tied to the vaccine as well. Then in September, after another participant in the British study fell ill with similar symptoms, AstraZeneca halted its trials globally but failed to promptly notify the U.S. authorities. They didn't rule out a link between the vaccine and clotting problems, though, and said they'd raise awareness of symptoms just in case. Still, the delay was a key reason that AstraZeneca fell so far behind the three other manufacturers whose vaccines have been granted emergency authorisation in the United States.