This US trial, which was attended by more than 32,000 participants, was the largest test of its kind for the shot. The results, AstraZeneca released on Monday, came from an interim look at the data after 141 Covid-19 cases occurred in volunteers.
The company had only announced on Tuesday how up-to-date this data was. This information is important because sometimes a more up-to-date look at clinical trial results may reveal different efficacy and safety.
If the analysis was done on data from a month or two ago, it is possible that a more recent look may give a different picture of the vaccine’s effectiveness and safety. The company has announced that it will provide the FDA with a more comprehensive and up-to-date dataset than it released on Monday. Although no clinical study is large enough to rule out extremely rare side effects, AstraZeneca reported that its study did not identify any serious safety issues.
The new data may have arrived too late to make a big difference in the United States, where the vaccine has not yet been approved and is not expected to be available until May. By then, federal officials say, there will be enough vaccine doses for all adults in the country from the three already approved vaccines: Pfizer-BioNTech, Moderna, and Johnson & Johnson.
Even so, the better-than-expected results have been seen as an encouraging turn for AstraZeneca’s shot, whose low cost and simple storage requirements have made it an important part of the quest to vaccinate the world.
The results were also believed to allay concerns about the AstraZeneca vaccine in Europe. Regulators there said the shot was “safe and effective” last week after conducting a review after a small number of people who had recently been vaccinated developed blood clots and abnormal bleeding. The US study found no evidence of such problems, although some real-world safety issues can only be identified when a drug or vaccine is widely used.
Millions of people have received the AstraZeneca shot worldwide, including more than 17 million in the UK and the European Union, almost all without serious side effects. To increase public confidence, many European political leaders have received the injections in the past few days. The AstraZeneca vaccine was also given to executives in South Korea, Taiwan and Thailand last week.
