This is the result of a joint analysis of Phase 3 studies underway in the UK and Brazil, with just over 11,600 people, as well as safety data from more than 23,700 study participants in the UK, Brazil and South Africa which is now being published.

The primary endpoint of the assay is symptomatic COVID-19 infection more than 14 days after the second dose of vaccine.

According to the findings — the first fully peer-reviewed efficacy results for the deployment of a coronavirus vaccine — the vaccine prevents symptomatic disease in 70 percent of cases.

The vaccine shows an effect of 62 percent in those who received two full doses of the vaccine — and 90 percent in those who received half a dose first, followed by a full dose one month later. In a combined analysis, this gives an average effect of 70 percent. The differences between doses remained after the researchers adjusted for differences in age and time between doses.

The researchers saw roughly the same thing when they looked at the effect 21 days after the first dose, indicating that a single dose could provide at least short-term protection.

The researchers also looked at the effect against asymptomatic disease. In the group that received half a dose followed by a full dose, the effect was 59 percent, while in those who received two full doses it was only 4 percent. However, the researchers stress that more data is needed to draw definite conclusions on this topic. The analysis is based on just 69 cases out of just over 6,600 people.

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And even when it comes to affecting the elderly, it is too early to draw conclusions. Just over 1,400 people in the initial analysis were over 55 years old. Only 4 percent are above 70.

Take a look at the results in The Lancet.