NSW Chief Health Officer Kerry Chant is hoping for a decline in COVID-19 cases by the end of the week but says people have to stick to the lockdown rules.

COVID-19 case numbers should soon start to fall in NSW if people adhere to lockdown rules, the state's top public health official says.

"I'm hoping that towards the end of the week we start to see a decline in case numbers," Chief Health Officer Kerry Chant told radio 2GB on Wednesday.

"But this really depends on how the community and businesses respond to our request to minimise those interactions and make sure they're COVID-safe," she said.

NSW recorded 19 cases in the 24 hours to 8pm on Monday, up from 18 the day before, averting the sharp increase authorities had feared.

Agriculture Minister, Adam Marshall, is just one of the latest cases after contracting the virus at a Paddington pizzeria last week.

Mr Marshall says he would be keen to get any available vaccine rather than wait for Pfizer, in light of Prime Minister Scott Morrison's announcement that under-40s can ask their GPs for AstraZeneca.

The 35-year-old told Channel Nine on Wednesday that his illness has been "debilitating and quite eye-opening".

"I'm very interested in the prime minister's announcement ... and I'm looking to get information," he said.

"The rollout's been an absolute shambles, to be honest ... we've got to pick up our game."

But Dr Chant stopped short of recommending younger people seek out AstraZeneca.

"Certainly I'm very committed to following the (Australian Technical Advisory Group on Immunisation) advice," she said.

The prime minister's snap decision on Monday to allow under-40s access to AstraZeneca contradicted official advice from ATAGI, which recommends AstraZeneca only be made available to people over 60.

Dr Chant urged those who've had their first AstraZeneca shot to get their second.

She said younger people should discuss the matter with their GPs. But GPs may well prioritise the elderly, she said.

Meanwhile, NSW has tightened the rules for people travelling into the state if they have visited other regions.

NSW Health says people from areas in the Northern Territory, Queensland, and Western Australia now subject to stay-at-home rules should not travel to the state unless permitted to do so.

From Wednesday, anyone coming to NSW who has been in those areas in the previous 14 days must complete a declaration form. This is the same requirement already in place for people who have been in Victoria in the previous 14 days.

NSW Health has also issued more than 20 new public health alerts for venues across Sydney visited by COVID positive cases, including gyms, restaurants, shops, clubs and hotels as well as some bus routes. All are listed on its website.

Wednesday marks the fourth day of lockdown for residents of Greater Sydney, Central Coast, Blue Mountains, Wollongong and Shellharbour regions.

The stay at home orders remain in place until at least July 9.

Premier Gladys Berejiklian has suggested that the transmissibility of the Delta strain means some restrictions will likely remain in place, even after the current cluster is eradicated and the lockdown ends.

She said the state needs to get 80 per cent of its adult population vaccinated before it can adjust to "COVID-normal" life and open up.

The state is just over 20 per cent of the way to that goal.

Some 149 people have contracted the coronavirus locally since June 16, when the first case was reported at Bondi in Sydney's east.