The CDC committee discussing the distribution of Covid-19 vaccines will convene an emergency meeting on Tuesday

A researcher at an Oxford vaccine team is working in a laboratory on a coronavirus vaccine developed by AstraZeneca and the University of Oxford. John Cairns / University of Oxford / AP

More information and research is needed to understand how the dosing regimen of AstraZeneca differs from efficacy and whether a new study is needed to check the effectiveness of the lower dose, World Health officials said in a press conference in Geneva on Friday.

“The first thing to say is that what we saw is a press release,” said Katherine O’Brien, WHO’s director of immunization, vaccination and biologics. “And what’s really the next most important step is that the data really doesn’t just have to be evaluated based on a press release.”

All that can be included in a release, he said, and that needs to be reviewed is the data that may arise during the review and the questions asked about it.

“It’s hard to consider,” O’Brien said. “I think we can still emphasize that what we understand from the press release is certainly something interesting that we observed, but there are a number of reasons that may underpin the differences observed.”

More information is needed, including evaluating the immune response during the study, he said.

Dr Soumya Swaminathan, a senior scientist at the WHO, agreed with O’Brien, saying that everything that is known comes from the press release and that it appears that less than 3,000 people received half and then the full dose of the vaccine.

It is also understandable that no one in this group was older than 55 years. The two groups that received the full dose were larger in number and had different age groups.

“It’s very hard to compare these two groups, and I’d say the numbers are still small enough to really draw definitive conclusions,” he said.

“Of course, the advantage of using a lower dose, especially if you get more efficacy, is great, and you can save on the vaccine and at the same time benefit from greater efficacy, but I think it’s speculation at this point,” he said.

Swaminathan said they heard that AstraZeneca would like to try a full dose on a half-dose full dosing schedule.

Remember: The U.S. Food and Drug Administration requires an efficiency of at least 50%. It is unclear whether the FDA approves emergency use.

AstraZeneca has not yet tested its half-strength dose in the US. But on Thursday, a company spokesman told CNN that the goal is to include the half-strength dosing regimen in their U.S. experiments, which currently has about 10,000 participants.