Australia won?t reach 80% Covid booster rate until well into 2022, analysis shows

Australia could take until well into next year to hit an 80% booster vaccination rate, with the rollout currently ranking almost last out of 70 countries, Guardian analysis shows.

Boosters are now available to anyone who has had a second dose of a Covid vaccine more than five months ago.

However, Australia's slow initial vaccine rollout meant that more than half of all second doses were administered in the final four months of 2021. So with a five-month dosing interval, the people who received their second doses late in 2021 won't be eligible for a booster until February.

Experts warn that a shorter interval between second and booster doses could mean the immune response is not as high or long lasting.

"We do know from evidence from the first two doses that a longer interval between the first dose and second dose gives you higher antibodies, higher protection," says Cyra Patel, a PhD candidate at the Australian National University.

"And that is consistent with our knowledge of immunology as well. We have seen that with other vaccines a longer interval gives you a better boosting effect. It's really a balance between getting you protection from another dose earlier and giving you better protection if you have a longer interval."

Analysis of vaccination data shows that roughly the same number of people have now had booster shots as were fully vaccinated about 170 days ago. This means the booster rate is still on track with a six-month interval.