Six people died in Pfizer’s late-stage trial of the COVID-19 vaccine, the US Food and Drug Administration has revealed just hours after Britain became the first country in the world to roll out the vaccine.

But the deaths are said to raise no new safety issues or questions about the vaccine’s effectiveness because all represented events that occurred in the general population at a similar rate, the FDA concluded.

Its 53-page briefing report, released on Wednesday morning (Australian time) is the first detailed analysis of the vaccine trial by Pfizer and BioNTech, which found in November that its vaccine was 95 per cent effective in preventing coronavirus infections.

The documents revealed that two people who received the experimental vaccine had died during the trial. Four others who died were on a placebo.

“All deaths represent events that occur in the general population of the age groups where they occurred, at a similar rate,” the report said.

It confirmed the vaccine was, as reported by Pfizer, 95 per cent effective at least seven days after the second injection.

Data shows the vaccine was just 52 percent effective after the first dose.