AstraZeneca (AZN.L) said on Friday its COVID-19 vaccine contributed $275 million in sales and shaved three cents per share from its first-quarter earnings. read more This marked the first time the Anglo-Swedish drugmaker has given financial details about the distribution and sales of its vaccine, which it developed with Oxford University. read more Here is a summary of the vaccine"s progress since inception: A team involving Oxford Vaccine Group and Jenner Institute begins developing a vaccine to prevent COVID-19. MARCH 2020: Oxford University researchers begin screening healthy volunteers, aged 18-55, for a ChAdOx1 nCoV-19 vaccine trial. Human trials begin. AstraZeneca joins forces with Oxford on development and potential distribution of the vaccine candidate. MAY 2020: AstraZeneca and Oxford start recruiting volunteers for a much larger human trial in the UK. JULY 2020: Initial safety data showed vaccine was safe and produced an immune response. AUGUST 2020: Vaccine candidate begins late-stage study in the United States. SEPTEMBER 2020: 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 rolling review process. OCTOBER 2020: EU launches real-time review of vaccine. United States restarts trial, the last one to do so after other regions. NOVEMBER 2020: AstraZeneca confirms that UK regulator has started an accelerated review of vaccine. Interim late-stage data from UK, South Africa trials released. On average it prevented 70% of COVID-19 cases in late-stage trials in Britain and Brazil. The success rate rose to 90% in a group of 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. DECEMBER 2020: Britain approves the shot in a 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. JANUARY 2021: India approves Serum"s vaccine in early January. Europe gives vaccine green light late January. FEBRUARY 2021: World Health Organisation gives vaccine the go-ahead. MARCH 2021: AstraZeneca cut first-quarter supply forecast to the EU due to export constraints. Austria halts use of one batch of vaccine after reports of cases of blood clots in Nordics. More than a dozen European countries, including Germany and France, halt use of the vaccine. read more European regulators and WHO back its safety in mid-March. In late March, interim data from late-stage trials in U.S., Peru, Chile shows vaccine is 79% effective. The U.S. National Institute of Allergy and Infectious Diseases said AstraZeneca may have included outdated information from the trial, providing an incomplete view of efficacy data. Norway keeps the vaccine on hold for another three weeks. Canada pauses use of the vaccine for under-55s. APRIL 2021: UK regulator found total of 30 cases of blood clot events after AstraZeneca vaccine use. EU drug regulator finds link between vaccine and blood clots, but benefits outweigh risks WHO reiterates AstraZeneca benefits outweigh risks. Oxford pauses vaccine study in children. Britain advises alternative to the vaccine for under-30s. EU drug regulator says up to countries to decide how to handle AstraZeneca distribution. Italy, Britain suggest age limits but still recommend it. Australia reports first blood clot death "likely" linked to the vaccine. Backs Pfizer over AstraZeneca for under-50s. Denmark ditches AstraZeneca"s COVID-19 shot. Canadian panel expands use of AstraZeneca doses. Chilean AstraZeneca trial saw no cases of blood clots. EU sues AstraZeneca over breach of COVID-19 vaccine supply contract, demands immediate access to UK-made vaccines Our Standards: The Thomson Reuters Trust Principles.