How has the UK's Covid vaccination rollout come to this? We started the year with a jabs programme that was the envy of much of the world. We successfully fought off a wave of infections with a rapid, careful and systematic rollout to those most vulnerable to the virus. But the ongoing row over whether to vaccinate healthy teenagers has led to another tetchy stand-off between politicians and scientists, parents and schools. And to what end?

The UK's Joint Committee on Vaccination and Immunisation (JCVI) has issued its latest advice on the question of jabs for children. It says that 'the health benefits from vaccination are marginally greater than the potential known harms', but 'the margin of benefit is considered too small to support universal vaccination of healthy 12- to 15-year-olds at this time'.

This is sensible and balanced advice. The committee maintains that 'the main focus should be the benefits to children themselves, balanced against any potential harms to them from vaccination'. This is an important ethical consideration, which guards against using children as mere means to the end of infection control. Given the minimal risk Covid poses to healthy children, any danger posed by the vaccine must be even smaller. And any social benefit of vaccinating the young needs to be extremely compelling. Considering that the vaccines do not seem to confer lifelong immunity nor prevent transmission of the virus to others, it's hard to see how vaccinating healthy kids will help much to protect the vulnerable from Covid.

The JCVI's recommendation is not the last word on the matter, however. Its advice is that the accumulation of 'longer-term data on potential adverse reactions' may 'allow for a reconsideration of the benefits and harms'. It could well be that the risk posed to children by the Covid jab turns out to be much smaller than is currently thought. But it could also turn out that jabbing children provides them with more limited protection than natural infection does. In that scenario, the case for vaccinating kids collapses, both in relation to their own health and to the pursuit of wider population immunity. Our understanding of the vaccines and of Covid itself is still evolving, and in that context the 'precautionary approach' recommended by the JCVI is wise.