AstraZeneca Plc’s antibody cocktail was effective at preventing people with mild or moderate COVID-19 infection from worsening in a study that bolsters the drugmaker’s ambitions for the product.

The cocktail halved the risk of developing severe illness or death compared with a placebo in 822 participants who had been symptomatic for a week or less and weren’t hospitalized, Astra said in a statement Monday.

The results are another boon for the injected product after it was also found to be highly effective at preventing symptomatic disease in high-risk people. The news comes after Merck & Co. fueled optimism that it will soon have the first Covid pill. Both treatments could offer a simple way to treat patients before they ever reach the hospital.

Astra shares rose less than 1% to 8,922 pence in early London trading.

The results are a relief for the U.K. drugmaker after an initial trial testing whether the cocktail could prevent symptomatic disease in people explicitly exposed to the virus failed in June. Astra said last week it had applied for emergency-use authorization in the U.S.

Antibody treatments are a key tool in the fight against Covid as they can be used to supplement vaccines for people who haven’t mounted a strong response to the shots or to protect those who couldn’t be immunized. Cancer sufferers or people with weakened immune systems could be eligible for such cocktails.

Global Trial

“With continued cases of serious Covid-19 infections across the globe, there is a significant need for new therapies like AZD7442 that can be used to protect vulnerable populations,” said Hugh Montgomery, the principal investigator on the trial and professor of intensive-care medicine at University College London.

The data on 822 people showed 18 cases of Covid worsening in the Astra group compared with 37 in the placebo arm. The cocktail was generally well tolerated.

The trial took place in countries including the U.K., Brazil, the U.S. and Germany. The company said it will submit the results for peer review.

In a separate analysis of patients who received treatment within five days of getting symptoms, the cocktail reduced the risk of the disease becoming more severe by 67%. The majority of patients—90%—were from populations at high risk of progression to severe illness. Many had other diseases such as diabetes and cancer.