A COVID-19 vaccine developed by the University of Oxford and AstraZeneca has shown “positive high-level results” in early data from clinical trials, researchers announced Monday. It is the third vaccine to clear that crucial hurdle, alongside ones made by Pfizer and Moderna.
The vaccine has been 70% effective on average so far, researchers said. The early data came with a potentially promising surprise: The vaccine was 90% effective for volunteers who were given a half-dose of the vaccine followed by a full dose — a much higher success rate than those who were given two full doses, which was 62% effective.
The early analysis was based on 131 COVID-19 cases among trial participants who either received the vaccine or a placebo injection. The underlying data have not yet been peer-reviewed or released to the public.
The trials, which took place in the UK and Brazil, also showed that the vaccine was highly effective in preventing hospitalizations or severe cases of the coronavirus. “These findings show that we have an effective vaccine that will save many lives,” professor Andrew Pollard, chief investigator of the Oxford vaccine trial, said in a press release.
Unlike the Pfizer and Moderna trials, which only tested people who reported symptoms, the AstraZeneca data also showed that asymptomatic infections were reduced in the group of patients who received a vaccine, suggesting that it can help limit transmission. The AstraZeneca trial in the UK swabbed patients weekly, which provided more information about who developed infections.
Earlier this month, Pfizer and Moderna announced that trials for their vaccines both suggest that they are more than 90% effective. The Food and Drug Administration requires a vaccine to be at least 50% effective before authorizing its use.
The Oxford-AstraZeneca vaccine is cheaper than the Pfizer or Moderna vaccines and may also be easier to store and transport.
AstraZeneca is requesting an “Emergency Use Listing” from the World Health Organization to make the vaccine quickly available in low-income countries. The company said it would begin discussions with the FDA this week about whether to formally submit for review in the US.
Researchers had to pause the vaccine’s effectiveness study twice, a development which is not unusual in clinical trials. In July, a patient developed multiple sclerosis, and in September another patient developed a neurological illness called transverse myelitis. The vaccine was not found to have caused either illness, and the trials resumed, leading to today’s preliminary results.
In its data release, the drug company said that “no serious safety events related to the vaccine have been confirmed.”