Two high-ranking officials at the World Health Organisation (WHO) consider that more profound data is needed on the efficiency of the vaccine developed by AstraZeneca and the University of Oxford.
According to Katherine O'Brien, director of WHO's immunisation and vaccines department, it is too early to judge the vaccine's efficiency before more scientific data is released on it.
"So I think it's too early for us to say anything about what we make of the data, and what is needed next - what we really need to see - is more than a press release and to really see the data, and have a chance to ask the questions that are needed", O'Brien said on Friday.
Soumya Swaminathan, a chief scientist at the WHO, also said that "if we are to explore this hypothesis of having perhaps a better efficacy with a lower dose, then it would need a trial".
Earlier in the day, the UK's Medicines and Healthcare products Regulatory Agency (MHRA) confirmed that AstraZeneca had requested it to conduct a review of the vaccine.
The interim test results of AstraZeneca's vaccine showed that efficacy in patients administered two full doses one month apart was 62 percent, while in those administered a half-dose and then a full dose, it reached 90 percent. The company later admitted that the regimen with a higher efficacy had actually been the result of a dosing mistake.
Following the controversy, AstraZeneca's CEO said on Thursday that the company would conduct additional international tests to erase all doubt, though it did not mention which country/countries will participate in it.