AstraZeneca (AZ) has updated results from a phase 3 trial of its COVID-19 vaccine conducted in the US, with a slightly lower efficacy rate than what was previously reported.
On Monday, AZ said that its Oxford University-partnered vaccine demonstrated a vaccine efficacy of 79% at preventing symptomatic COVID-19, as well as 100% efficacy at preventing severe disease and hospitalisation, based on an interim analysis.
The researchers also reported that the vaccine efficacy was consistent across ethnicity and age, with participants aged 65 years and over demonstrating a vaccine efficacy of 80%.
Shortly after that, the US data and safety monitoring board (DSMB) notified the US National Institute of Allergy and Infectious Diseases (NIAID), the Biomedical Advanced Research and Development Authority (BARDA) and AZ about the initial COVID-19 vaccine trial data.
According to a statement from NIAID, the DSMB was concerned that AZ may have included outdated information from the trial, which could have provided an ‘incomplete view’ of the efficacy data.
In response, AZ said it will engage ‘immediately’ with the DSMB to share the primary analysis with the up-to-date efficacy data.
The primary analysis of the trial confirmed the vaccine efficacy, with a slightly lower efficacy rate of 76% reported in the updated results.
The vaccine efficacy increased slightly in the 65 years and older age group, with a new reported efficacy of 85% in this population.
The key secondary endpoint of preventing severe or critical disease and hospitalisation due to COVID-19 also remained consistent at 100%.
AZ added that the vaccine was well tolerated, with no new safety concerns identified for the vaccine.
“The primary analysis is consistent with our previously released interim analysis, and confirms that our COVID-19 vaccine is highly effective in adults, including those aged 65 years and over,” said Mene Panagalos, executive vice president, BioPharmaceuticals R&D, AZ.
“We look forward to filing our regulatory submission for emergency use authorisation in the US and preparing for the roll-out of millions of doses across America,” he added.
The concerns over the US trial data for AZ’s vaccine came following a safety review from the European Medicines Agency (EMA) over reports of blood clots in people who had received the jab.
Last week, the EMA said the vaccine was safe to use following a careful review, confirming that the benefits of the AZ vaccine continue to outweigh the risk of side effects.
The EMA’s safety committee PRAC also confirmed that the vaccine is not associated with an increase in the overall risk of blood clots.