The coronavirus vaccine developed by AstraZeneca and the University of Oxford offered strong protection against Covid-19 in a large clinical trial in the United States Comprehensive protection against the worst effects of the disease without causing serious side effects, according to data released on Monday.

The results, announced in a press release from AstraZeneca, could help build global confidence in the vaccine. In the United States, where the vaccine has not yet been approved and may not be needed, the new data may not make a difference.

If AstraZeneca gets emergency approval in the US based on the new results, the vaccine will likely not be available until May, when federal officials predict that three other approved vaccine manufacturers will produce enough doses for all adults in the country.

The announcement comes at a very tense time for AstraZeneca. More than a dozen countries temporarily suspended vaccinations this month to address concerns about possible rare side effects. This is the latest result of a series of problems facing AstraZeneca that have undermined the confidence of both the public and some government officials.

Most countries will resume use of the shot after the European Union Medicines Agency announced Thursday that a review found the vaccine to be safe. However, the speed at which several nations stopped using the vaccine reflected a reluctance about its safety and effectiveness that contrasts sharply with the confidence shown in other countries Vaccinations.

AstraZeneca said Monday it will continue to analyze the new data and prepare to apply for an emergency permit with the Food and Drug Administration. The vaccine has already been approved in more than 70 countries, but regulatory clearance when the company can secure it would be a boost for the company.

The US study also recruited participants from Chile and Peru. It found AstraZeneca’s vaccine was 79 percent effective at preventing symptomatic infections. The vaccine was particularly good at preventing serious diseases, with 100 percent effectiveness in this regard in the subjects who received the vaccine – a major selling point for the shot.

Overall efficacy was greater than that seen in previous clinical trials of the vaccine, despite being used on a dosing schedule that may not be optimal. Oxford said the number could be affected by the thresholds set for symptomatic Covid-19 cases.

The study found no serious side effects, a comforting sign. European regulators launched the latest safety clearance after a small number of people in Europe who had recently been vaccinated suffered blood clots and abnormal bleeding.

Regulators found the vaccine didn’t increase the overall risk of blood clots, but said they couldn’t rule out the possibility of a link between the vaccine and a rare complication that causes bleeding in the brain. A new warning label will be added to the recording to help doctors keep an eye out for any possible evidence of the disease.