The interval change kicks in from October 4, so anyone who has received their first dose of Pfizer will be able to bring forward their second vaccination.

The vaccine booking system will be updated overnight on October 3.

There will also be a shift in 88,000 Moderna vaccine doses from community pharmacies to state clinics to hasten the rollout, with pharmacists struggling to cope with the sudden demand.

"It's very difficult for pharmacists and others to go from zero to hundreds and hundreds of thousands of doses administered in the early stages," Premier Daniel Andrews told reporters.

Victoria has reached the 80 per cent milestone of first vaccine doses for the eligible population.

The landmark comes, however, as the state sees a troublesome shift in case numbers.

Another 1438 new locally acquired infections and five deaths have been recorded.

The jump is being blamed on illegal social gatherings.

"This is more than a 50 per cent increase on yesterday's daily numbers and I'm sure that'll be of great concern to all Victorians," Mr Andrews said.

"We were very clear those numbers would go up. They go up faster, of course, if people don't follow the rules."

He again urged Victorians to stop visiting each other in their homes and breaching public health orders.

"The contact tracers tell us that there are significant numbers of social gatherings on Friday and Saturday over a long weekend. Grand final parties, other social gatherings, barbecues, backyard visits, all of this generating significant and additional case loads," COVID-19 Commander Jeroen Weimar told reporters.

"We know that everyone's fatigued. We know everyone's tired of this. But today is a significant setback in how we manage this outbreak."

If Thursday's case number jump becomes a trend, Victoria will go from being just below the case projections done by the Burnet Institute, which is guiding the state's road out of lockdown, to being in the worst scenario, Mr Weimar says.

The new case numbers brings the total active cases in the state to 11,018 and the death toll of the current outbreak to 41.

With lockdown continuing until vaccination milestones are reached, the state and federal governments are extending a jointly funded business grants package for six more weeks.

Up to $2.27 billion for small to medium-sized businesses was announced on Thursday for those most affected by restrictions as Victoria reaches the 70 per cent, then 80 per cent, fully vaccinated thresholds, forecast for about October 26 and November 5, respectively.

More than 160,000 businesses will be eligible for the support, ranging from retailers and gyms to hairdressers and hotels - mostly through automatic deposits into their bank accounts.

Also from Thursday, Victorian residents keen to return from extreme risk zones such as Greater Sydney can apply for a permit if they are fully vaccinated, test negative within 72 hours of departure and isolate at home for 14 days.

Those who have been to an exposure site, are close contacts of a COVID-19 case or have symptoms will be knocked back, while non-Victorians are not eligible.

For exposure sites visit www.coronavirus.vic.gov.au/exposure-sites

Australian Associated Press