Research has found places where infection rates were low will be reliant on booster shots to prevent further waves, as there are low levels of herd immunity.

This will be crucial for the ACT as protection from the vaccine wanes. Less than 0.5 per cent of the territory's population has been infected with the virus.

Research, published in the New England Journal of Medicine, found Pfizer vaccines offered at least 90 per cent protection against severe COVID-19 cases for at least six months.

However, six months after the second Pfizer dose the vaccine offered less than 20 per cent protection against milder infections of the virus.

The co-author of the research, epidemiologist and Aspen Medical group medical director Andrew Jeremijenko, said further research had also suggested booster shots would be essential in communities, like Canberra, where there had been low levels of infection.

"We don't have the high natural infection rates and so if we don't do booster shots we're at higher risk of insurgence," Dr Jeremijenko said.

"If we don't implement booster shots because we don't have a high natural immunity we will have higher infection rates so that's where booster shots are so important."

The ACT government opened bookings for its booster shot program on Monday, with people who received the vaccine at least six months ago eligible for their top-up.

A majority of the territory's population won't be eligible for the booster shot until 2022.

Deputy chief health officer Vanessa Johnston said the booster shot was incredibly important in ensuring longer lasting immunity.

"I think there's still a lot of emerging evidence internationally and here nationally about the bump in immunity that is going to give us," she said.

"Long term, we're still a little bit unsure about how regularly these vaccines are going to need to be administered, whether it be annually or not.

"The case rate has been lower so we haven't had that natural immunity so much and we do know that the immunity from the vaccine is very protective."

Dr Jeremijenko likened Australia's possible experience to Israel, which had a spike in cases six months after its vaccination program started. Israel, comparatively, had lower levels of infection and as the vaccine protection decreased there was a third wave.

Boosters shots were rolled out to combat this. However, for those fully vaccinated who were infected had less severe infections and there was a lower death rate.

Dr Jeremijenko, who has conducted research on the matter, said the experience had been different in Qatar where there had been a higher infection rate during the initial wave. Following its vaccination program there was not a large resurgence in cases.

"Israel is closer to Australia than Qatar. Qatar didn't have that resurgence because it already had a lot of natural immunity plus vaccination," he said

"Natural infection plus vaccination is even better than just vaccination alone... that's really what a booster shot does it basically stops you having a natural infection."

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The ACT government has expressed concern that take-up of booster shots could lag.

Research commissioned by the government found a portion of the population had received the jab reluctantly and targeted campaigns may be needed to ensure this group will come forward for booster shots.

Health Minister Rachel Stephen-Smith said this reluctance was unlikely to be seen in the people who are eligible for booster shots at present.

"My suspicion is that those people who, particularly older people who received their first two shots of AstraZeneca, will be very enthusiastic about getting an mRNA vaccine booster as well, just to really increase their protection against the worst outcomes from COVID-19," she said.

"I suspect that our health staff who obviously were very early in the rollout will also be enthusiastic about getting their booster shots."

"There may be some other people who just sort of wait and see and consider themselves to be fully vaccinated.

"I think it's a little bit hard to tell at this point in time, how much enthusiasm we're going to see for the boosters."

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