ROME: COVID-19 infections in adults of all ages fell by 80% five weeks after a first dose of Pfizer , Moderna or AstraZeneca vaccine, according to Italian research published on Saturday.

The first such study by a European Union country on the real-world impact of its immunisation campaign was carried out by Italy's National Institute of Health (ISS) and the Ministry of Health on 13.7 million people vaccinated nationwide.

Scientists started studying data from the day Italy's vaccination campaign began, on Dec. 27 2020, until May 3 2021.

The analysis showed that the risk of SARS-CoV-2 infection, hospitalisation, and death decreased progressively after the first two weeks following the initial vaccination.

"As of 35 days after the first dose, there is an 80% reduction in infections, 90% reduction in hospitalisations, and 95% reduction in deaths," the ISS said, adding that the same pattern was seen in both men and women regardless of age.

"This data confirms the effectiveness of the vaccination campaign and the need to achieve high coverage across the population quickly to end the emergency," ISS president Silvio Brusaferro said in the statement.

Among the nearly 14 million people included in the Italian study, 95% of those who had taken Pfizer and Moderna had completed the vaccine cycle, while none of those given AstraZeneca had received a second dose.

Up until now, Italy has been following the makers' recommendations, giving a second dose of Pfizer three weeks after the first, a second dose of Moderna after a four week gap and a second dose of AstraZeneca after a 12 week gap.

As of Saturday morning, some 8.3 million Italians, or 14% of the population, were completely vaccinated, while around 10 million people had received a first jab.