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US trial reports AZ Covid-19 jab safe and effective, with no blood clot link

By Darcy Jimenez 22 Mar 2021 (Last Updated March 22nd, 2021 17:47)

The US Phase III trial of AstraZeneca’s Covid-19 vaccine has demonstrated an efficacy of 79% at preventing symptomatic Covid-19, and 100% efficacy at preventing severe disease and hospitalisation.

US trial reports AZ Covid-19 jab safe and effective, with no blood clot link
The Phase III trial showed AZ’s Covid-19 vaccine to be reliably effective among those aged 65 years and over, in whom the jab demonstrated an efficacy of 80%. Credit: AstraZeneca

The US Phase III trial of AstraZeneca’s Covid-19 vaccine has demonstrated an efficacy of 79% at preventing symptomatic Covid-19, and 100% efficacy at preventing severe disease and hospitalisation.

A specific review of thrombotic events and cerebral venous sinus thrombosis during the trial, conducted by the independent safety monitoring board and an independent neurologist, found no increased risk of thrombosis among the 21,583 trial participants receiving at least one dose of the vaccine.

The review findings come after several European countries paused rollouts of the AstraZeneca-Oxford University vaccine, following reports of blood clotting events in a small number of those vaccinated.

The European Medicines Agency last week concluded that the vaccine is “safe and effective” following an investigation into a potential link between the jab and blood clots, while the World Health Organisation urged countries to continue administering the vaccine.

The randomised Phase III trial also showed the vaccine to be reliably effective among those aged 65 years and over, in whom the jab demonstrated an efficacy of 80%.

The results among older participants confirm the vaccine’s efficacy in those aged over 65. Earlier this year, numerous European countries decided to limit the AstraZeneca vaccine to under-65s, citing a lack of evidence for the vaccine in the older age group. Several of these countries, including Germany and France, have since approved the jab for use in older people in response to the publication of further safety and efficacy data.

In the Phase III study, around 20% of participants were aged 65 or older, and approximately 60% had co-morbidities associated with an increased risk for progression of severe Covid-19, such as diabetes, severe obesity or cardiac disease.

The trial involved a total of 32,449 participants – two-thirds of whom received the vaccine – across 88 sites in the US, Peru and Chile.

University of Rochester School of Medicine professor Ann Falsey, one of the principal investigators for the trial, said: “These findings reconfirm previous results observed in AZD1222 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.”

The new data, which AstraZeneca will continue to analyse, is set to be submitted to the US Food and Drug Administration for Emergency Use Authorisation in the coming weeks. The vaccine has already been approved for emergency use in the UK, European Union and many other countries globally.

AstraZeneca executive vice president of biopharmaceuticals R&D Mene Pangalos said: “These results add to the growing body of evidence that shows this vaccine is well tolerated and highly effective against all severities of Covid-19 and across all age groups.

“We are confident this vaccine can play an important role in protecting millions of people worldwide against this lethal virus. We are preparing to submit these findings to the US Food and Drug Administration and for the rollout of millions of doses across America should the vaccine be granted US Emergency Use Authorisation.”