Pharmaceutical company AstraZeneca on Monday announced that advanced trial data from a United States study showed that its coronavirus vaccine was 79% effective in preventing symptomatic cases and was 100% effective in stopping severe disease and hospitalisation.

The results of the late-stage human trial study of more than 32,449 volunteers across all age groups was published on Monday. While 20,000 participants were given the vaccine, the rest got dummy shots. AstraZeneca has produced the vaccine in collaboration with Oxford University.

AstraZeneca said results of participants aged 65 years and above showed the vaccine to have an efficacy of 80%. In February, Oxford’s vaccine trial chief Andrew Pollard had said that the shots produced good immune responses in older people even if there was a lack of data about its exact efficacy.

Although more than 50 countries have authorised the use of AstraZeneca’s vaccine, it has not received the same permission in the US. The findings are just one set of information that the company must submit to the US Food and Drug Administration. An FDA advisory committee will then publicly debate the evidence submitted before deciding whether to allow its emergency use.

The result of the trial was announced days after many European countries suspended the use of the AstraZeneca vaccine following reports of unusual blood clots in vaccine recipients. However, after the European Medicines Agency said the jab was “safe and effective”, many countries announced restarting its use.

Countries that suspended the use included Denmark, Norway, Iceland, Germany, France, Italy, Ireland, Bulgaria, The Netherlands, Austria, Estonia, Latvia, Lithuania and Luxemburg.

Before the European drug regulator’s announcement, the World Health Organization and the United Kingdom, besides the company itself, had defended the vaccine. The WHO had urged the countries to resume the inoculation programme, saying that the risk-benefit (ratio of risk to its potential benefits) of using AstraZeneca vaccines outweighed the risk of Covid-19 infection.

In India, the AstraZeneca-Oxford vaccine is one of the two vaccines approved for emergency use. Covaxin, developed by Bharat Biotech in collaboration with the Indian Council of Medical Research and the National Institute of Virology, is the other vaccine.