Under National, foreigners who haven't had a COVID-19 vaccine might not be allowed in the country.
Leader Judith Collins told The AM Show on Wednesday she "can't see why we would" let tourists in if there was a chance they could be carrying the virus, which has killed almost 1 million people worldwide in the past nine months.
"Why would we do that? ... I don't think people are going to want to have people come into New Zealand with COVID-19."
There is not yet a vaccine for the virus. Several dozen are being developed, but estimates on when an effective and safe vaccine will be available range wildly.
US President Donald Trump, who has regularly made false claims about COVID-19, said on Monday a vaccine would be ready "within a matter of weeks", while experts say it could be several years. Phase III trials, in which thousands of people are given the vaccine candidate, can take years to run - and the first potential COVID-19 vaccines have just entered this phase.
National has proposed setting up a dedicated Border Protection Agency to run the quarantine and isolation system, and requiring homecoming Kiwis to have a negative test for COVID-19 before even getting on the plane.
Asked if she would put sanctions on Kiwis who refuse to take a COVID-19 vaccine when one was available, Collins said she wouldn't - relying instead on peer pressure.
"All their neighbours would probably sanction them... I think most New Zealanders are sensible enough to understand that they should get vaccinated."
She would personally have it as "someone who understands vaccinations".
Prime Minister Jacinda Ardern on Tuesday said if she keeps her job after October's election, she wouldn't impose sanctions on those who refuse to get the jab either.
"We haven't for any vaccination in New Zealand applied penalties in that way," Ardern told The AM Show. "But I would say for anyone who doesn't take up an effective and tested and safe vaccine when it's available, that will come at a risk to them."
If enough Kiwis get vaccinated, it creates herd immunity - by reducing the chance of the virus finding a new host to infect, those who can't get vaccinated for health or age reasons are protected too.
Australian Prime Minister Scott Morrison said in August a COVID-19 vaccine will be mandatory in Australia for those without complicating health conditions, hoping for 95 percent take-up.
"If you look at the levels of vaccination we manage to reach in New Zealand, they are high," said Ardern.
People talk about anti-vaxxers - actually, the bigger issue in New Zealand is more than Dr Bloomfield calls vaccination hesitancy. It's not people who are strongly morally opposed - it's more people who just need a bit of extra support, remove the barriers, a bit more information.
"I see no reason to [have penalties]. We get up well over 90 percent for our vaccinations without that, and I believe we will for this."