AstraZeneca downgrades vaccine effectiveness from 79% to 76%

AstraZeneca has issued an updated phase three trial data for its COVID-19 vaccine on Wednesday, after facing criticism on its accuracy over a preliminary report from its U.S. study, earlier this week.

The UK-based company said in the updated report that the vaccine was 76 per cent effective (down from 79 per cent reported on Monday) in protecting against symptomatic cases of the virus and 100 per cent effective against severe disease and hospitalisation.

The update came after U.S. health officials criticised the company for selecting data to make the results appear more favourable.

The U.S. National Institute of Allergy and Infectious Diseases revealed on Tuesday that AstraZeneca might have included outdated information in trial results of its COVID-19 vaccine, potentially casting doubt over published efficacy rates, despite the findings of a large U.S. trial showing that the vaccine is safe and highly effective.

The updated results included data collected from 190 symptomatic cases, across more than 32,000 participants — an increase of roughly 50 symptomatic cases studied compared with the data set AstraZeneca released on Monday.

The findings suggested the vaccine was more effective in patients aged 65 and older than previously understood, with a newly reported efficacy rate of 85 per cent for that population, up from a previously stated 80 per cent.

AstraZeneca confirmed on Wednesday that the vaccine was “well-tolerated” among participants and identified no safety concerns.

It was reported last week that the Oxford-AstraZeneca vaccine rollout was halted in several countries after reports of blood clots in some vaccinated people.

Health experts immediately criticised the precautionary measure in response, citing a lack of data, while analysts expressed concern about the impact on vaccine uptake as the virus continues to spread.

Countries like Germany, France, Italy and Spain, which had initially suspended the vaccine’s rollout, have backtracked.

They took the decision after Europe’s drug regulator said its initial investigation of possible side effects concluded the shot was safe and effective, adding the benefits of administering the vaccine still outweigh the risks.