Washington, Mar 23 (IANS): Results from a large clinical trial in the US and South America indicate that the AstraZeneca Covid-19 vaccine is well-tolerated and protects against symptomatic Covid-19 disease, the American National Institutes of Health (NIH) said.

The independent Data and Safety Monitoring Board (DSMB) formed by the NIH overseeing the trial identified no safety concerns related to the vaccine, AZD1222, Xinhua news agency quoted the medical research agency as saying in a statement on Monday.

The placebo-controlled trial began in August 2020.

The analysis is based on results from 32,449 adult volunteer participants enrolled across 88 sites in the US, Chile and Peru.

One participant received a placebo for every two participants who received AZD1222, resulting in approximately 20,000 people receiving the investigational vaccine.

The vaccine was administered in two doses four weeks apart.

AZD1222 demonstrated statistically significant vaccine efficacy of 78.9 percent in preventing symptomatic Covid-19 and 100 percent efficacy in preventing severe or critical disease and hospitalisation, according to the NIH.

In participants 65 years and older, vaccine efficacy against symptomatic Covid-19 was 79.9 percent.

The DSMB conducted a review of blood clots and cerebral venous sinus thrombosis among participants and found no increased risk of these conditions in vaccinated participants, said the NIH.