A Covid-19 vaccine developed by the University of Oxford and AstraZeneca Plc prevented a majority of people from getting the disease but fell short of the high bar set by Pfizer Inc. and Moderna Inc., according to initial results of a large trial.
The vaccine stopped an average of 70% of participants in a study from falling ill, an early analysis of the data show.
The results combined data from two different dosing regimens, which may leave questions about the best way to give the AstraZeneca shot. One regimen, given to some 2,700 people, showed efficacy of 90%, while another, given to nearly 9,000 people, showed 62% efficacy.
The best results were obtained by inoculating volunteers with a half dose of vaccine, before using a full dose a month later.
The results look less promising than data from Moderna, which said its shot stopped 94.5% of trial participants from falling ill, according to early data. Pfizer, which is working with German partner BioNTech SE, said its vaccine candidate prevented 95% of symptomatic infections.
The findings were reviewed after 131 trial participants contracted Covid-19.
Astra said there were no serious adverse safety events and the vaccine was tolerated well across both dosing groups. There were no severe cases of Covid-19 in the trial and no participants were hospitalized.
Despite the lower efficacy, the British shot has some advantages when it comes to distribution. While the other two have to be stored frozen, the Astra-Oxford jab can be kept at refrigerator temperature, which would make it easier to transport and store globally, particularly in lower and middle-income countries. It also comes at a potentially lower cost.