The number of Victorian COVID-19 patients in intensive care remains stable despite the state adding 1240 new infections to its caseload.

As a result of the continuing high infection rate face masks are here to stay but any return to restrictions or lockdowns is off the table, says Acting Premier James Merlino.

Neither will the state consider again altering visitor requirements.

"Public health have made it clear across the country that border arrangements aren't going to help," Mr Merlino told reporters in Melbourne on Sunday.

"So no changes to border arrangements, no changes to capacity at events, no changes to density, there's no changes to limits in households and celebrating Christmas and New Year.

"All we are continuing to do are some prudent measures while we learn more and that's around particularly face masks."

Victoria is now managing 13,093 active coronavirus cases in total. There are 392 virus patients in hospitals across the state, 81 of them in intensive care and 41 requiring ventilation.

There were 384 people with infections in hospitals on Saturday, 84 in ICUs and 43 on ventilators. The seven-day hospitalisation average has risen marginally to 380.

A further four virus-related deaths were also announced on Sunday.

Health officials say virus testers managed to process more than 76,000 results in the 24 hours to Saturday evening.

Mr Merlino said opening times at centres had been extended considering the number of people wanting to be tested as they prepared for leave or holiday travel during Christmas week.

With demand high, capacity had been increased by about 55 per cent since October with around 260 sites across Victoria now in operation.

"I know that there are particular sites where the wait is long but the average is 45 minutes to an hour or so," Mr Merlino said.

"I ask people to be patient. We're expanding and extending it as much as we can."

The state is currently 92 per cent fully vaccinated for people 12 and over, although almost 500,000 Victorians are overdue a vaccine booster, out of more than 750,000 currently eligible five months after their second dose.

A pre-Christmas vaccine booster blitz is underway as capacity ramps up at state-run clinics and major hubs stay open to help "turbo-charge" the rollout.

The government previously flagged it would close eight state-run vaccination clinics by mid-December.

However the Royal Exhibition Building clinic remained open for walk-up appointments from 8.30am to 3.30pm on Sunday and will also operate from 8am to 8pm Monday to Thursday.

The Wyndham drive-through clinic will also stay open from 8.30am to 4.30pm each day with no bookings required.

All 58 state-run vaccination clinics are offering walk-up Pfizer booster appointments in the lead-up to Christmas, as well as bookings, and walk-up Moderna boosters will be available from Monday.

Mr Merlino says Victoria's Omicron count stands at 24 cases, 16 acquired overseas.

The figure is up five on Saturday's count and as authorities continued to determine whether there were further infections among patrons at two Melbourne nightclubs.

Meanwhile, the government has announced international travellers who touch down in Melbourne from Tuesday will no longer have to isolate for 72 hours after they arrive.

Instead, those fully vaccinated will have to take a test within 24 hours of arrival and isolate until they receive a negative result.