Winter is coming. You can tell because the days are drawing in, the light has that autumnal greyness, and the first bloody advent calendars are in the shops. Also, those of us who are old, pregnant or still in nappies are reminded reminded to take our flu jabs.
The Telegraph, among other outlets, is reporting that two million UK children will be eligible for the new nasal-spray influenza vaccine this year; it's been extended to include four-year-olds as well as the two- and three-year-olds who were eligible last year.
I'm hugely wary of any sort of criticism of vaccination programmes, because the sort of people who criticise them are usually homeopathy-using cranks who think the CIA is controlling them through their tooth fillings, and because vaccination is clearly one of the great public health breakthroughs of the last two centuries. What's worse, media criticism of vaccines was behind the MMR catastrophe, which led to thousands of children needlessly catching measles.
So when the NHS says you should take your flu vaccines, children and old people, I think you should listen to them. But the flu vaccine is an interesting case: unlike the MMR jab, the evidence for its effectiveness is far less clear-cut.
The Cochrane Library has done reviews both into the jabs for older people and into the nasal sprays for children and found, in both cases, that much more work is needed before either can be shown to be a cost-effective way of preventing the disease.
Cochrane reviews, which are systematic examinations of the evidence for a treatment, are a wonderful shortcut for science writers like me: if a Cochrane review says something, it's almost certainly right. And they found that, in the case of flu jabs for the elderly, there have been lots of poor-quality studies, but only one good, proper, randomised control trial - and that one had too few participants to give a good picture of possible complications. 'The available evidence is of poor quality and provides no guidance regarding the safety, efficacy or effectiveness of influenza vaccines', it says.
The evidence in favour of the nasal spray for children is rather better - children over the age of two, at least, for whom it is recommended by the NHS. But Cochrane has also warned that too much of the evidence comes from industry-funded trials, which have a tendency to overstate the efficacy of a treatment.
None of this is to tell you not to get vaccinated. The NHS and Public Health England both recommend it, and they don't do so for fun: the flu killed nearly 100 people in Britain last year, mainly the elderly, and hospitalised thousands more. But you should be aware that the evidence for the vaccine's effectiveness, especially in the elderly, is not yet as good as it could be. Even if you get your jabs, you still need to take other steps to avoid infection.