Pharmaceutical giant AstraZeneca on Tuesday revealed it had hit a setback in trials of a treatment for Covid-19 symptoms.

The drug, made from a combination of two antibodies, failed its main goal to treat symptoms in exposed patients, the company said in a statement.

The treatment has been undergoing phase 3 or final-stage clinical trials to assess its safety and efficacy.

AstraZeneca said that 1,121 unvaccinated adults had been exposed to an infected person as part of the trial.

Treatment AZD7442 reduced the risk of developing symptoms by only 33 percent -- which was "not statistically significant", it added.

The company is nevertheless continuing trials to assess whether the drug can prevent Covid or treat more severe symptoms.

The US government has funded the development of AZD7442 and has agreements to receive 700,000 doses.

Meanwhile, AstraZeneca's Covid vaccine, which was developed with the University of Oxford, faced fresh safety doubts.

The jab has been suspended in several European countries over reports of rare blood clots.

A top official in the European Medicines Agency was on Sunday reported as having suggested that it might be worth abandoning AstraZeneca's vaccine if alternatives were available.

But the EMA said the body's head of vaccine strategy, Marco Cavaleri, had been misrepresented, and that he believed its benefits outweigh its risks.

"The decision on its use in different populations and ages is the prerogative of the EU Member States, based on specific factors such as virus circulation and vaccine availability," a spokeswoman said.

A study from British health authorities published on Monday found that two doses of AstraZeneca/Oxford or rival Pfizer/BioNTech vaccines stopped the need for in-patient treatment in more than 90 percent of cases of the Delta variant.

The UK government on Monday announced a four-week delay to the full lifting of coronavirus restrictions in England due to a surge in infections caused by Delta, which first appeared in India.