Coronavirus cases across all age groups in Italy fell by 80 per cent after the first five weeks of vaccine rollout, the country's National Institute of Health (ISS) and the Ministry of Health said in a joint statement.

The time covered by the comprehensive national report on the real-world effectiveness of coronavirus vaccines runs from December 27, 2020, when the national vaccination campaign started, through May 3, Xinhua news agency quoted the statement as saying on Saturday.

In broad terms, the statement said that the risk associated with Covid-19 decreased progressively starting two weeks after the first vaccination, and that as of 35 days from the first dose the data showed "an 80 per cent reduction in infections, a 90 per cent reduction in hospitalisations, and a 95 per cent reduction in deaths", and a similar pattern was seen regardless of gender and 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," said Silvio Brusaferro, president of ISS.

The fact that the strong results were shown after the first dose of the AstraZeneca, Pfizer-BioNTech, or Moderna vaccines is significant, because the makers of those vaccines say a second dose given three to 12 weeks after the first (depending on the vaccine) is required for full protection.

The Johnson & Johnson vaccine requires a single dose to be effective.

As of Saturday, over 26.6 million vaccine doses had been administered throughout Italy.

A total of 8.4 million residents, or 14.1 per cent of the population, have been fully vaccinated.