Cases of coronavirus are expected to peak “late next month” in Wales, Mark Drakeford has said.

The First Minister said new infections were highest among the under-25s, with the gap between younger age groups and the more vulnerable over-60s potentially showing the “positive impact” of vaccination.

On Friday, Wales became the first country in the UK to fully vaccinate 50% of the population, with the Welsh Government aiming to offer second doses to all adults by the end of September.

The country is one week into a four-week pause in relaxing restrictions to allow scientists to determine whether vaccinations have broken the link between getting ill from the disease and needing hospital treatment.

Mr Drakeford said the number of cases of the more transmissible Delta variant, first identified in India, had more than doubled in a week to about 1,100 cases, and that previous waves had shown there was a four-week lag between infections and an increase in the number of people admitted to hospital and deaths.

At Friday’s government press briefing he said: “If this wave follows the same pattern, we can expect to see these peaking in August.

“What we don’t yet know is what impact our high rates of vaccination will have and how much the relationship between infections on the one hand, and hospitalisations on the other, has been weakened by vaccination.”

But Mr Drakeford said there was “positive research evidence” that Covid-19 vaccines were helping to prevent serious illness, despite the Delta variant, and urged people to have both doses.

The incidence rate of Covid across Wales has risen to 37 cases per 100,000 people, the highest since March, and is highest in North Wales, where four of the six local authority areas have rates higher than 50 cases per 100,000.

Mr Drakeford said 15 people have so far been admitted to hospital, having contracted the Delta variant, in Wales.

Of those being infected, Mr Drakeford said Wales was following a similar pattern to England, where the higher proportion are within younger people who are not yet vaccinated.

The infection rate is about 67 cases per 100,000 people in the under-25s, compared with just nine cases per 100,000 for the over-60s.

“This is why we are working so hard to speed up the vaccination programme while we have temporarily paused any further changes to the restrictions and why we are encouraging everyone to have two doses of the vaccine,” he said.

Mr Drakeford said take-up rates of the jab have been “fantastic”, although there were “some small signs of hesitancy” among those aged 30 to 39.

He also repeated that the four-week pause should be enough for advisers to determine whether vaccines are stopping people needing admission to hospital.

“I remain hopeful that by the time I stand here next time I will have had advice of a definitively sufficient sort for me to be able to say to people, either things are not looking good and we can’t move ahead, or we’re pretty confident enough that vaccination has altered the relationship between illness and hospitalisation and… we can go ahead with some further moves to restore people’s freedoms,” he said.