From today, Kiwis aged over 30 will be able to access Pfizer's updated XBB.1.5 vaccine. Photo / Sylvie Whinray
From today, Kiwis aged over 30 will be able to access Pfizer's updated XBB.1.5 vaccine. Photo / Sylvie Whinray
From today, Kiwis over 30 will be able to access the latest Covid-19 vaccine. How does it work and what makes it better than the last one? Science reporter Jamie Morton explains.
What makes this vaccine different?
By training our bodies on how to make the “spike protein” the coronavirususes to hack into our cells – and then stimulating an immune response against it – the new vaccine works much in the same way Pfizer’s previous Covid-19 shots have.
But because that spike protein changes as the virus morphs to dodge our defences, vaccines need to be updated to combat the latest strains.
Whereas the most recent shot rolled out here targeted both the “original” virus and the Omicron subvariants behind 2022′s winter wave, the one available from today is more closely matched to the XBB.1.5 strain.
“It means the immune system is solely focused on responding to this slightly morphed variant,” University of Auckland vaccinologist Associate Professor Helen Petousis-Harris said.
Responsible for many Covid-19 cases last year, this strain has itself since been largely squeezed out of circulation by the surprisingly dominant JN.1 - but most of what’s spreading today is descended from or closely related to XBB.1.5.
How effective is it?
Given the vaccine has been in use for less than a year – NZ is behind many other countries in deploying it – “real-world” data on how well it works is limited.
But early studies show promising results, especially when it comes to the vaccine’s main job: preventing severe sickness.
One from Denmark indicated it reduced the risk of hospitalisation among older people by 76 per cent, compared with those who hadn’t been boosted in the short-term.
Another focused on older people and carried out in the Netherlands suggested it to be similarly effective at keeping people out of hospital and intensive care.
Among younger people, Petousis-Harris said, there was evidence indicating it could more than halve Covid-related visits to the doctor.
“It can also reduce transmission, because recently vaccinated people shed less infectious virus compared with people who have not been recently vaccinated.”
University of Auckland vaccinologist Helen Petousis-Harris. Photo / Dan Cook, RNZ
For those worried about Long Covid, vaccinations received over time reduced the risk, said the Immunisation Advisory Centre’s medical adviser, Dr Joan Ingram.
“This is called a dose-response relationship: one dose of vaccine reduces risk by 21 per cent, two doses reduce risk by 59 per cent, and three-plus doses reduce risk by 73 per cent, according to a Swedish study that followed nearly 600,000 patients through [autumn in] 2022.”
Can everyone get it?
As with the last vaccine, Te Whatu Ora has restricted free eligibility to Kiwis aged over 30, with exceptions for high-risk people aged over 12, and those who are pregnant and older than 16.
“The risk of severe disease is low in healthy people under 30 years of age,” Ingram said.
Te Whatu Ora Health New Zealand national public health service national director, Dr Nick Chamberlain, said the Government wasn’t looking at changes to access.
“If we were to consider changes to the eligibility criteria, we’d consult publicly to ensure feedback from the healthcare sector and the community is considered before making a decision.”
Chamberlain said the vaccine was “especially recommended” to more vulnerable groups, including over-65-year-olds, Māori and Pasifika people aged over 50, and those severely immunocompromised.
When’s the best time to get it?
For most of us, it’s a good idea to get the vaccine if it’s been at least six months since your last boost – or infection.
“If you had a Christmas dose of Covid, then you’d perhaps be looking at the middle of the year as the best time to get boosted,” Petousis-Harris said.
In a population now well-exposed to the virus, she said most Kiwis would now have “hybrid immunity” - or background protection conferred from both the vaccine and infection.
But Te Whatu Ora data suggested there were still hundreds of thousands of people who hadn’t bothered to seek another jab since their first booster – and could benefit from a dose better suited to what’s spreading now.
“Though it’s not easy to do comparisons these days, generally speaking, vaccines have been shown to be a little better at boosting immunity than infection itself,” Petousis-Harris said.
If not through your local GP clinic or pharmacy, you can get the new vaccine by booking online at bookmyvaccine.health.nz, or phoning 0800 28 29 26 on weekdays.
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
