AstraZeneca’s US trial shows 79% efficacy against Covid

AstraZeneca’s US clinical trial of its Covid-19 vaccine developed with Oxford university has shown 79 per cent efficacy at preventing symptomatic disease and 100 per cent efficacy against severe or critical disease and hospitalisation.

A fifth of the participants in the trial were over the age of 65 and the jab showed 80 per cent efficacy in these older participants, the long-awaited results showed on Monday.

The AstraZeneca vaccine is currently embroiled in a safety row in Europe, with at least 16 countries pausing or limiting its rollout after registering a series of rare side events involving a specific type of blood clot.

The European Medicines Agency has said that the vaccine’s benefits far outweigh its risks, but some countries have opted to continue to halt the rollout, pending more data. An EMA probe last week found no link to blood clotting in general, but left the door open to the possibility of a link to a rare combination of events that include blood clots in the brain, a low platelet count, and bleeding.

Crucially, the US trial found the vaccine was well tolerated, AstraZeneca said, and the independent data safety monitoring board identified no safety concerns related to the vaccine.

In particular, the group reviewed the “thrombotic events”, including cerebral venous sinus thrombosis, which have caused concern across Europe, with the assistance of an independent neurologist.

The monitoring board found no increased risk of thrombosis or events characterised by thrombosis among the 21,583 participants receiving at least one dose of the vaccine. The specific search for CVST found no cases in this trial.

The vaccine, easy to store and transport and currently sold at cost, is also at the centre of a diplomatic row between the EU and the UK, with the former threatening to block exports of jabs, including AstraZeneca doses, to the latter.

AstraZeneca’s US trial involved 32,449 people, including 141 symptomatic cases of Covid-19. London-listed shares in the drugmaker gained at least 1.1 per cent shortly after the open.

Ann Falsey, professor of medicine at the University of Rochester and a principal investigator for the trial, said: “These findings reconfirm previous results observed in [earlier] trials across all adult populations but it’s exciting to see similar efficacy results in people over 65 for the first time.

“This analysis validates the AstraZeneca Covid-19 vaccine as a much-needed additional vaccination option, offering confidence that adults of all ages can benefit from protection against the virus,” she said.

Mene Pangalos, executive vice-president of biopharmaceuticals R&D at AstraZeneca, said the company was preparing to submit the findings to the US Food and Drug Administration for approval.

Vaccines made by BioNTech/Pfizer, Moderna and Johnson & Johnson have shown varying degrees of efficacy against symptomatic Covid-19 in trials, but they have all been shown to be effective in preventing severe disease and death.