A third wave of Covid cases is likely and "the question is how big will this wave be", Wales' health minister has warned.
Eluned Morgan said she was concerned about the Delta variant spreading after a cluster of cases in Conwy county.
And she said it would be "difficult to stop the flow from England".
A surge in Covid cases in parts of the UK is being partly driven by the increased transmissibility of the Delta variant, which was identified in India.
There are 97 cases of the Delta variant in Wales, including 35 cases in Llandudno, Llandudno Junction and Penrhyn Bay.
And children at a primary school in Merthyr Tydfil have been told to stay home for another week after a visitor tested positive for the variant.
"A third wave is likely. It will be difficult to stop the flow from England, the question is how big will this wave be," said Ms Morgan.
"We are worried that the spread of the virus is so much higher with the Delta variant and that's why the latest lifting of restrictions is in two parts.
"We have allowed three households to come together outdoors but we are waiting a few weeks for more data to be clearer that this variant is not spreading throughout our society and how it affects our hospitals.
"But it must be emphasised how successful the vaccination programme is and we have to learn to live with this virus and keep the NHS safe by minimising the number of patients that need hospital treatment."
More than 68% people in Wales have had a first vaccine and 37.5% have had a second, according to figures published on Friday.
Another 300,000 people could get the jab in the next two weeks, Ms Morgan told BBC Radio Cymru.
UK Health Secretary Matt Hancock told the BBC's Andrew Marr programme that the Delta variant was "more challenging".
Former White House senior adviser for coronavirus response has described the Delta variant, first identified in India, as “COVID-19 on steroids” and urged Americans to get vaccinated against the virus.
The toll that the coronavirus pandemic has exacted on the Israeli public isn’t fully reflected in the number of fatalities, the number of infected patients or figures on those required to go into quarantine.
The European Union is about to launch a digital pass system that will let residents prove they have been vaccinated against COVID-19, recovered from the disease or recently tested negative for the virus, allowing them to travel freely among all 27 member nations.
Russia reported another sharp rise in fresh COVID-19 cases on June 13, a day after the mayor of Moscow told residents of the Russian capital to say home from work next week to curb the spread of the virus.