A healthcare worker prepares to inject a vaccine against AstraZeneca coronavirus disease (COVID-19).

Eloisa Lopez

AstraZeneca released updated Phase 3 trial data for its Covid-19 vaccine on Wednesday after asking accuracy questions related to a preliminary report from its US study earlier this week.

The company now says its vaccine is 76% effective against symptomatic virus cases. A press release published on Monday reported a symptomatic efficacy rate of 79%. The updated report claims the shot is 100% effective against serious illness and hospital stays.

A group of US health officials criticized the company over the past few days for claiming that they are collecting data to make the results seem more favorable.

The National Institute of Allergy and Infectious Diseases announced Tuesday that the UK-based company may have included information from its US findings that provided an “incomplete view of efficacy data”.

AstraZeneca said at the time that the numbers were based on a “pre-determined interim analysis” and promised to share the updated analysis in the coming days.

Dr. Anthony Fauci, Chief Medical Officer and White House Director at NIAID, described the situation as “unfortunate” and said it was likely that AstraZeneca would issue a modified statement.

“This is really what you call an easy mistake as it is most likely a very good vaccine,” Fauci told ABC’s Robin Roberts on Good Morning America Tuesday. “Something like that … really creates doubts about the vaccines and maybe adds to hesitation. It wasn’t necessary.”

The updated results include data from 190 symptomatic cases in more than 32,000 participants – an increase of around 50 symptomatic cases studied compared to the dataset published Monday.

The results suggest that the vaccine is more effective than previously thought in patients aged 65 and over, with a newly reported efficacy rate of 85% for this population versus 80% previously reported.

AstraZeneca reiterated Wednesday that the vaccine was “well tolerated” among participants and that no safety concerns were identified.

AstraZeneca has faced a separate backlash over the past few weeks due to reports of blood clotting related to its vaccine, which is already approved and used by dozen of countries around the world. Several European nations have suspended and then resumed use of the vaccine after independent safety reviews.

– CNBC’s Berkeley Lovelace Jr., Sam Meredith, and Steve Kopack contributed to this report.