THE global covid-19 vaccine roll-out is accelerating, with in excess of 300 million doses now administered. This time last year, such an achievement would have been almost a pipe dream.

Great challenges remain in ensuring the equitable distribution of vaccines across the world and persuading those who are hesitant that vaccination is in their best interests and in the interests of those around them. But even in countries where vaccines are available and take-up is high, emerging issues threaten the success of comprehensive vaccination programmes.

One concern is that the vaccination strategies of some countries might not be the best path in the long term. Vaccinating the most vulnerable people first will undoubtedly save lives now, but could spur the emergence of potentially dangerous “escape” variants of the virus, and come at significant cost further down the road.

Meanwhile, countries such as Australia, New Zealand and Thailand that have successfully kept the coronavirus out face different challenges. With minimal cases to contend with, these places aren’t desperate for vaccines to save lives now. But as much of the rest of the world becomes vaccinated, it will be difficult to reconcile their zero-covid border policies with those of countries learning to live – and allow travel – with the virus in some form.

“Vaccinating the most vulnerable will save lives now, but might not be the best long-term strategy”

Finally, we know that the vaccines won’t work for everyone, which may dent the effectiveness of roll-out programmes. How can we find out whether we are still at risk after having had a jab?

Promise on this front comes in the form of commercial tests that offer to measure precise levels of antibodies in the blood after infection or vaccination. Theoretically, it should be possible to keep an eye on these over time to see when levels are waning. Unfortunately, it seems doubtful whether the tests currently live up to the hope.

Many of the answers to these quandaries lie in determining how much the virus can spread even among those who have been inoculated. Until then, vaccination won’t be the jab-and-go solution many of us will have hoped for.