The Welsh government has drawn up a “Covid urgent” plan designed to deal with any new coronavirus crisis that threatens to overwhelm the NHS this autumn and winter.

If the plan has to be brought in, it could mean that the Covid alert level for Wales, currently at zero, might be increased and restrictions reimposed.

However, the Labour-led government stressed it believed it was more likely that the country would be able to operate under a planning scenario it is calling “Covid stable”, in which Wales remains at alert level 0 through the autumn and winter, with all businesses staying open.

On Friday, the first minister, Mark Drakeford, is publishing an updated coronavirus control plan for the next few months.

Drakeford said on Thursday evening that Wales would remain at alert level 0 for the next three weeks, meaning all businesses are open. But he added: “We are facing a challenging winter ahead – coronavirus hasn’t gone away and flu is forecast to return this winter.” He urged everyone to be vaccinated for Covid – and all those who were eligible to also get a flu jab.

The latest version of the coronavirus control plan sets out two planning scenarios for the pandemic. In the first, Covid stable, Wales remains at alert level 0 through the autumn and winter, with all businesses able to open.

A Welsh government spokesperson said: “This is thought to be the most likely scenario for the future, as we become used to living with coronavirus and we gradually move out of the pandemic to a position where the virus becomes a seasonal illness.

“Under this scenario, if case rates fall, measures could be relaxed further in response, and if they rise, some existing measures could be strengthened to protect people’s health.”

The second planning scenario, Covid urgent, is designed to deal with any sudden changes to the situation, caused by the emergence of a new, fast-spreading variant or if vaccine immunity levels fall, causing a rise in pandemic pressures, which risk overwhelming the NHS.

The spokesperson said in such a scenario, the alert level system and restrictions would be used “proportionately”, but as a last resort.

Drakeford has made it clear he is determined to act cautiously this autumn and winter. People must still wear face masks in busy public places and the Labour-led government wants people to work from home whenever possible. A Covid pass to get into nightclubs and sporting events comes into force on Monday.

The Welsh government also announced on Thursday evening it would change its restrictions on international travel to keep them in line with England’s.

But the health minister, Eluned Morgan, said her government has urged the UK to take a “more precautionary approach”, adding: “We are concerned about the cumulative impact of the risk being carried in relation to opening up travel particularly from higher risk countries.”

Meanwhile, Andrew RT Davies, the leader of the Welsh Conservatives in the Senedd, said he was taking a “complete break” on doctor’s orders to focus on his recovery, having caught flu and Covid-19, which he said had taken a toll on his mental health.