Coronavirus: Vaccines

AstraZeneca says vaccine 80% effective for elderly, no blood clot risk

WASHINGTON • AstraZeneca has said its Covid-19 vaccine is 80 per cent effective at preventing the disease in the elderly and does not increase the risk of blood clots, following its phase three efficiency trial in the United States.

The vaccine was 79 per cent effective at preventing symptomatic Covid-19 in the overall population and 100 per cent effective at preventing severe disease and hospitalisation, it said yesterday.

Several countries had advised against administering the jab to older people due to a lack of data among elderly participants in previous trials. Earlier this month, several countries also paused use of the AstraZeneca shot over fears it may cause blood clots.

The US phase three trial of the vaccine developed by AstraZeneca and Oxford University involved 32,449 participants, with two-thirds receiving the jab, the pharmaceutical firm said in a statement. Around 20 per cent were 65 or older, and about 60 per cent had health conditions associated with a higher risk of severe Covid-19 such as diabetes, severe obesity or cardiac disease.

"These findings reconfirm previous results observed in AZD1222 trials across all adult populations, but it is exciting to see similar efficacy results in people over 65 for the first time," said professor of medicine Ann Falsey of the University of Rochester School of Medicine, the trial's co-lead principal investigator.

The trial's independent data safety monitoring board found no increased risk of thrombosis among the 21,583 participants who received at least one dose, the statement said. Some leading European Union countries have resumed AstraZeneca vaccinations after the European Medicines Agency said last Thursday that the jab was "safe and effective" and was not linked to an increased risk of blood clots.

AstraZeneca said it was preparing to submit its findings to the US Food and Drug Administration to authorise the shot for emergency use. The results also suggested that administering the second shot more than four weeks after the first could further increase efficacy. Previous trials have shown leaving up to 12 weeks between jabs increased its efficacy.


A version of this article appeared in the print edition of The Straits Times on March 23, 2021, with the headline 'AstraZeneca says vaccine 80% effective for elderly, no blood clot risk'. Subscribe