Research from the UK suggests a 12 week gap between the first and second doses of the Covid vaccine is better than a shorter time:
Experience from the UK’s Covid-19 vaccination rollout suggests 12 weeks may be the optimum gap between first and second doses, giving a better immune response than when the doses are closer together. So why are so many New Zealanders being offered their vaccines three weeks apart?
When the British Government launched its vaccination programme, the big gap between first and second doses was more a function of necessity than science.
The strategy was primarily focused on getting one dose in the arm of as many citizens as possible, with the second dose coming later, when supply ramped up.
Isn’t that the scenario here? We don’t have enough vaccines to give enough people, including those deemed to be more vulnerable to Covid-19, the first dose.
That gap between doses mostly ended up being two to three months apart.
But as researchers looked at the results, they found that the delay turned out to have another major benefit. “The bigger the gap you can leave between vaccines the better the immune response”, Cambridge University consultant clinical virologist Dr Chris Smith told RNZ. “Twelve weeks was de rigueur.”
Same message from a June 2021 study from the University of Birmingham and Public Health England: “Antibody response in people aged over 80 is three-and-a-half times greater in those who have the second dose of the Pfizer Covid-19 vaccine after 12 weeks compared to those who have it at a three-week interval.” . .
The World Health Organization recently talked about 21 to 28-day intervals between Pfizer doses, but says the second dose can be extended to 12 weeks to gain coverage for high priority populations.
In contrast to the UK, New Zealand has adopted a different strategy, focusing on optimising two doses for our most vulnerable citizens and minimising the gap between doses, in some cases, to as few as three weeks.
The UK research tells us that a more successful rollout strategy for New Zealand should look less like New Zealand in June 2021 (above).
Instead, it should look more like the UK in March 2021 (below) . . .
Is it better to have more people partially vaccinated or around half as many fully vaccinated?
What we do know is that New Zealand is a country with zero-community cases, and as Associate Professor Nathan Bartlett of the University of Newcastle’s School of Biomedical Sciences and Pharmacy put so clearly: “The improved immunity conferred from waiting longer must be weighed against the risk of contracting Covid in the meantime.”
As there is little to no risk of contracting Covid-19 in New Zealand, it seems logical that New Zealand should focus on improving immunity over the longer term – and that currently suggests a longer gap between doses. . .
If 12 weeks between doses gives better protection than a shorter gap a change in strategy to delay the second dose for most people could provide two benefits. More people could get the partial protection from a first dose and then get better long term protection from a bigger gap before the second dose is given.
Given we have no community transmission at the moment and a shortage of vaccines, using the supplies scheduled for second doses to give more people a first dose seems to be better than double dosing fewer people sooner.