From Wednesday, Pfizer eligibility expands to people aged 16 to 39 across Victoria's 55 vaccination hubs as supply ramps up courtesy of 175,000 doses imported from Poland.

Some under-40s in Ballarat reported to The Courier the process was slow but they have secured appointments within the fortnight, even after the website timed out.

Others have been left waiting until early November for the first available bookings, despite trying via the website from 7am when bookings opened.

Premier Daniel Andrews said more than 830,000 vaccination bookings over the next four weeks will be made available from 7am on Wednesday, including 450,000 first-dose Pfizer appointments.

Bookings would only be taken via the COVID hotline from 8am.

Those aged 18 to 39 who have already made a first dose AstraZeneca appointment will be given the option to instead receive the Pfizer jab, while 16- to 17-year-olds will strictly receive the latter.

But within minutes of bookings opening, the website appeared to buckle.

Many young people reported receiving a "500 internal server error" after waiting in the queue to book their appointment, while others were told they were ineligible for the vaccine.

It comes as Victoria recorded 50 new coronavirus cases on Tuesday, of which 39 were infectious in the community and 10 are yet to be linked.

Seven of the new infections live in Shepparton, about 180 kilometres north of Melbourne, bringing the total outbreak there to 44 cases. That cluster has been genomically linked to an earlier outbreak in the Melbourne suburb of Glenroy.

Five more cases were also confirmed among the family of a previously announced COVID-positive resident in Lara, north of Geelong.

There are now more than 700 exposure sites across the state, including 11 in the Geelong area.

Melbourne has spent three weeks under strict stay-at-home orders, while regional Victoria re-entered lockdown on Saturday afternoon.

Mr Andrews said it was still too soon to say if the lockdown would be lifted as planned on September 2.

AAP