AstraZeneca Covid-19 vaccine's 90% efficacy came in younger trial group

The dose of AstraZeneca’s Covid vaccine that showed the highest level of effectiveness was tested in a younger population than a bigger dose that showed less efficacy, according to the head of the US Operation Warp Speed program.

The vaccine being developed with Oxford University was 90 per cent effective when a half-dose was given before a full-dose booster, the partners said on Monday. However, that regime was administered to participants in a group whose age was capped at 55, Warp Speed’s Moncef Slaoui said Tuesday in a phone call with reporters.

Researchers have been puzzling about the AstraZeneca report