New studies confirm waning immunity over six months after vaccination, imposing greater urgency around booster shots for the elderly and vulnerable
The promise of a classic Kiwi summer has been dangled in front of Aucklanders to convince them to either put up with lockdown or go get vaccinated.
Much of the discourse from Prime Minister Jacinda Ardern’s podium has used the threat of not being able to participate in summer events or travel out to holiday destinations in other regions to seek to drive up the vaccination rates in Auckland.
The entire concept of different freedoms afforded to the vaccinated and withheld from the unvaccinated will hinge on vaccine certificates - which the Ministry of Health has announced will be called ‘My Vaccine Pass’.
Once the traffic light system is in place, vaccinated Kiwis can expect life to open up again - with hospitality and retail able to return to their previous lives, and travel outside of Auckland back on the cards - although the logistics of 30,000 Aucklanders going through border checkpoints a day have yet to be explained.
But what the Ministry of Health’s marketing is calling the “pass to summer” may be mistaking vaccination for full protection and immunity.
Studies have confirmed the mRNA vaccine is not just ‘one and done’ - or indeed even two and done. Studies have shown that six months after being full-vaccinated, the effectiveness of the vaccine is reduced.
A study published last month found vaccine effectiveness for the fully-vaccinated decreased as time went by, declining from 88 percent during the first month down to 47 percent after five months.
This doesn’t mean the vaccine doesn’t provide the most protection possible - especially as early clinical trials found higher antibody levels after the second dose than those found in people who had natural immunity from actually getting Covid.
However, with many of New Zealand’s vulnerable and elderly having had their jab in the first half of the year, when the vaccine roll-out began in earnest, questions have been raised about who should be considered fully-protected when it comes to vaccine passes and who should be first in line for booster shots.
Vaccine pass with a use by date
Former National MP Dr Parmjeet Parmar, who has a PhD in biological sciences, wonders what this means for vaccine passes.
“Vaccine passports are to show that the person is vaccinated and therefore have a lower risk of contracting and spreading Covid-19,” she said. “This was a concept that seemed plausible when it was first announced, before we knew about waning of vaccine-induced immunity towards Covid-19.”
Parmar argues the purpose of the vaccine certificate is to state the person holding it is fully protected - but without consideration for how long it has been since people got the jab, the usefulness of the entire system is compromised.
“If you are a holder of a vaccine passport, basically you are saying to other people that you are fully immunised, and that you are safe - as safe as you can be. That’s the assurance we are looking for,” she said. But now with the news that the people at the front of the queue to get vaccinated early in the year will already have less protection from the virus, she’s not sure that assurance is really there.
And with the booster shot roll-out for the general public still in planning stages, its some of the most vulnerable New Zealanders who may be affected.
“Much like many other countries, we decided to get our most vulnerable - elderly and frontline workers - vaccinated first when we started vaccination for Covid-19 in February this year,” Parmar said. “This decrease in immunity does not mean no protection at all. But it is believed that it will have more impact on the elderly who were first in the queue.”
Studies are ongoing to examine the continual waning of immunity after vaccination and to determine whether a single booster shot will fix the problem, or if a long-term programme of revaccination will be necessary.
However, nine months from the beginning of vaccination in New Zealand, the studies suggest those who were prioritised in our vaccine rollout may need to re-up sooner than later.
It seems the Ministry of Health is well aware of this risk, with plans for expiry dates on the soon-to-be released vaccine certificates.
“The vaccine certificates contain an expiry date. More information on this will be released soon,” said National Digital Services group manager Michael Dreyer.
But, like so much of the Government’s Covid-19 response during 2021, the deadline dividing success and failure is immutable.
With certificates promised for general public use over the summer and Medsafe approving a third dose of the Pfizer vaccine as a booster shot just this week, the response may be just in time to prevent infection amongst the newly less-protected.
A high number of people were vaccinated over the past few months, due to the coincidence of the latest outbreak, younger age groups gaining access and massive coordinated drives such as Super Saturday.
This means a significant number will only need to get a booster come autumn - which should be ample time for vaccine certificates with expiry dates and to lock down booster shot supply.
But right now, weeks from Jacinda Ardern’s “strong promise” of Auckland opening back up, early adopters of the vaccine may have less immunity than was previously thought.
Parmar said the decline was surprisingly quick.
“Its not a diminishing slow process like we see with some other vaccines,” she said. “It happens faster than we have experienced with some other vaccines before.”
In comparison, the tetanus vaccine comes with a recommended booster shot every decade.
University of Auckland epidemiologist Rod Jackson said boosters are almost certainly going to be recommended in the near future.
“There is already discussion internationally about boosters possibly being a requirement for a valid vaccine certificate, although I don’t think this has happened anywhere yet,” he said. "However, this is a rapidly changing field and there are likely to be more effective vaccines coming in the next year or so.”
He agreed boosters were going to be a likely requirement of a valid vaccination certificate, however it remains to be seen how effective and long-lasting future vaccines will be.
Different kinds of immunity
With studies in this area nascent and ongoing, there are still many unknowns.
While it can be said that waning immunity increases your likelihood of picking up the virus, vaccination may still provide a longer-lasting protection that decreases the chances of people becoming severely ill.
Waning immunity after vaccination is linked to a drop-off in antibody numbers - the proteins that neutralise the virus before it can enter the cell.
However, the layer of protection within the cells could potentially have more staying power.
Studies have found T cells, which attack the infection once it happens, and B cells, which produce a new fleet of antibodies after re-exposure to the coronavirus, don’t drop in numbers at the same rate - in fact, B cells tend to get better at dealing with the virus over time.
Faced with the difficult task of getting the majority of the population vaccinated, it makes sense that Jacinda Ardern hasn’t been able to go into every last detail of T cell and B cell immunity from the podium.
Officials have endeavoured to keep the message simple and clear - vaccination is the best available way to protect yourself from the virus.
But leaving discussion of waning immunity may have emboldened people who see it as a sign of the vaccine being ineffective.
The heckler at the Prime Minister’s outdoor press conference in Kawakawa last week was shouting questions about the highly-vaccinated population of Israel experiencing a resurgence of the virus.
The documented tapering of antibodies answers his questions pretty squarely, without casting doubt on vaccination as an effective public health strategy.
But it's not information Kiwis are getting from the Government now.
“We need to talk about vaccination and immunity side by side,” Parmar said.
The idea that simply having been vaccinated ensures protection is already out-dated - examining the immunity of the population alongside vaccination rates would provide a clearer picture of how protected New Zealanders are.
But Parmar doesn’t think the news about waning immunity will further dissuade the unvaccinated from finding a centre and rolling up their sleeves.
“Waning immunity should create more pressure on people to get the vaccine,” she said. “Besides, a vaccinated population means more asymptomatic cases, which could mean more cases floating around the community. This means an increased risk for unvaccinated people.”
“If it’s your body, your choice,” she said. “Why do you make the choice for your body to suffer from Covid-19?”
