The looming question for New Zealand over booster shots next year is likely to be as much about politics as medical expertise.
While we're going through our rollout, a somewhat heated debate is under way overseas about extra, third doses.
There are different medical issues being weighed.
There have been hints of reduced vaccine protection against all, basic, Covid infection - months after shots. There's a continuing need to spread vaccines around the world; a question of who needs boosters the most; and whether it is better to give an extra dose of the original vaccine or wait for new versions tweaked to target variants such as Delta.
There are also political pressures and the vaccine makers are pushing for doses.
Governments want to be responsive to people's desire to have the best immunity they can at a tricky time when some restrictions are easing in various countries only to be replaced by new ones. In Britain's case some previous restrictions could be on the way back. Britain plans a fairly wide booster programme ahead of the northern winter for people aged 50 and above, the medically vulnerable, and health workers.
And maybe it is just prudent to top up immunity to reduce Covid infections and pressure on health systems. As with flu jabs, there would likely be an economic benefit just in reducing moderate Covid infections and the need for sick days to recover from them.
This would be a change to what the vaccines were intended for, which was to keep people out of hospital and prevent Covid deaths.
The United States' Biden Administration is keen for a general booster campaign if health agencies agree. The Centres for Disease Control and Prevention has said the vaccines still offer high protection against severe illness and death. On Saturday a Food and Drug Administration expert panel recommended boosters for people 65 and older, and those at medical and job exposure high risk, but voted against a top-up for anyone over 16.
A number of US medical experts have previously said that current evidence supports specific groups needing boosters - such as those aged over 60 and people who have weak immune systems because of health problems - rather than populations at large.
Prominent US epidemiologist and CNN analyst Dr Celine Gounder does not believe a third dose for the general public is needed yet and that a focus on boosters takes attention away from other measures such as masks, upgrading building ventilation and air filtration, and testing.
She tweeted: "We need to figure out the endgame & strategy that doesn't involve boosters every 6 months. We need to use ALL the tools in our toolbox, not just vaccines".
Scientists writing in the Lancet concluded that "the unvaccinated are still the major drivers of transmission". They said the focus should be more on shots targeting variants. "There is an opportunity now to study variant-based boosters before there is widespread need for them."
The World Health Organisation is opposed to the use of boosters in wealthy countries while many people around the world lack access to Covid vaccines. The basic problem there is not the worth of boosters, but the insufficient supply of doses. Vaccine production needs to be on a much bigger scale.
For an island nation like New Zealand, planning to keep incoming infections low under a regime of less restricted borders, it might make sense to give booster shots to frontline border, health and essential workers to aid community protection.
There has already been a clamour for booster shots to be organised now. If extra doses for all becomes the norm overseas, people will want that here.