(Reuters) - AstraZeneca published updated results from its major U.S. COVID-19 vaccine trial, after health officials there publicly criticized it for using "outdated information" to show how well the immunization worked.
On Thursday, AstraZeneca said its COVID-19 vaccine was 76% effective in the new analysis of the U.S. trial, a tad lower than the level reported earlier.
Here's a look at the progress of the vaccine development to date since its inception.
A team involving Oxford Vaccine Group and Jenner Institute starts work on developing a vaccine to prevent COVID-19.
Researchers at the Oxford University begin screening healthy volunteers, aged 18-55, for recruitment in the ChAdOx1 nCoV-19 vaccine trial in the Thames Valley Region.
Human trials begin
AstraZeneca and Oxford join forces for development and potential large scale distribution of the vaccine candidate.
AstraZeneca and Oxford start recruiting volunteers for a much larger human trial in the UK.
Initial safety data released showed vaccine was safe and produced an immune response.
Vaccine candidate begins late-stage study in the United States.
AstraZeneca suspends global trials due to an unexplained illness in a study participant.
AstraZeneca resumes UK trials.
Oxford/AstraZeneca begin submitting data to the UK regulator under a rolling review process.
EU launches real-time review of the vaccine.
United States restarts trial, the last one to do so after other regions began resumption much earlier.
AstraZeneca confirms that the UK regulator has started an accelerated review of vaccine.
Interim late-stage data from UK, South Africa trials released:
The vaccine on average prevented 70% of COVID-19 cases in late-stage trials in Britain and Brazil.
The success rate rose to 90% in a group of trial participants who accidentally received a half dose followed by a full dose.
The efficacy was 62% if the full dose was given twice, as it was for most study participants.
Russia's sovereign wealth fund says AstraZeneca will begin clinical trials to test a combination of its experimental COVID-19 vaccine with Russia's Sputnik V shot in hopes to boost efficacy.
Britain approves shot in first for COVID-19 vaccines in the West. Regulators said that the higher efficacy seen in the half-dose/full-dose cohort was likely a result of a longer gap between doses, rather than the amount of vaccine given.
India approves Serum's vaccine days later in early January.
Europe gives vaccine green light in late January.
The World Health Organisation gives the vaccine a go-ahead.
AstraZeneca cut its first-quarter supply forecast to the EU due to export constraints.
Austria halts use of one batch of vaccine following reports of cases of blood clots in Nordic countries.
More than a dozen European countries, including Germany and France, followed suit and halted use of the vaccine.
European regulators and WHO back vaccine's safety in mid-March, but poll shows European confidence has taken a hit.
In late March, interim data from late-stage trials in U.S., Peru, Chile shows vaccine is 79% effective.
Just after, the U.S. National Institute of Allergy and Infectious Diseases said the drugmaker may have included outdated information from the trial, providing an incomplete view of the efficacy data.
AstraZeneca issues clarification on interim study, adding that data was based on data through Feb. 17
Canada backs vaccine, but updates label to include information on blood clots.
(Reporting by Pushkala Aripaka, Yadarisa Shabong and Vishwadha Chander in Bengaluru; Editing by Hugh Lawson and Emelia Sithole-Matarise)