AstraZeneca said on Monday that the COVID-19 vaccine is effective in reducing both mild and serious forms of the disease and showed better than expected results in recent studies.
The company said in a press release that trials in Chile, Peru and the United States found the vaccine, developed in collaboration with Oxford University, was 79 percent effective in preventing symptomatic COVID-19 and posed no increased risk of blood clots.
The company hoped that the US will likely authorise the use of the vaccine.
It said the two-dose vaccine was equally effective in people over 65, where it had 80 percent efficacy.
The company said the study identified no new safety concerns, specifically no risk of blood clots, a concern which led many European nations to pause their vaccine rollouts last week.
The European Medicines Agency said last week the vaccine’s benefits outweighed its risks. The study also did not see a specific type of clot in blood vessels near the brain that the EMA said might be associated with the vaccine. However, this type of clot, called a cerebral venous sinus thrombosis, is so rare it might not be expected to occur in even a large clinical trial.
The latest data should help address some of those concerns, analysts said. Based on more than 32,000 volunteers, the trial was larger and elderly volunteers featured more prominently than in previous trial results from the UK which had prompted some European countries to initially hold back using the AstraZeneca shot on older people.
The volunteers included 79 percent white, 22 percent Hispanic or Latino, 8 percent Black, 4 percent Native American, and 4 percent Asian. About 20 percent of participants were 65 years and over, and approximately 60 percent had other health problems that can worsen COVID-19 like diabetes, severe obesity, or heart disease.
Studies of the vaccine have been stopped sue to various reasons. The US study was stopped for well over a month after a patient had a cerebral hemorrhage that was later determined to be unrelated to the vaccine. Later, early trial results in the UK, South Africa and Brazil left many experts scratching their heads, as the second dose of the vaccine seemed to decrease its efficacy.
South Africa halted its own rollout of the vaccine in February after a small study showed the two-shot vaccine might not be as effective against a new variant of the coronavirus that causes COVID-19 that is circulating there.
The two-dose AstraZeneca vaccine, like the one-dose vaccine developed by Johnson & Johnson, uses a modified common cold virus, known as an adenovirus, to ferry genetic code for a key component of the SARS-CoV-2 virus known as the spike protein into recipients’ cells. The cells make this protein, which is then recognised as foreign by the immune system. The result is that the recipient becomes protected against the virus.
