In the uk there is a roll out in schools of the flu mist nasal spray. What long term tests have been done? How effective IS it as opposed to claims and how frequent are side effects

The flu mist is a live virus sprayed up the nose, and the evidence on its school rollout is thin on exactly the tests you would want: long-term safety studies comparing vaccinated to unvaccinated children.

The retrieval surfaced mostly short-term studies on small groups, animal models, or cost modeling. One study from England in 2015-2016 found that in vaccine-eligible children, getting the nasal spray cut the chance of being hospitalised with lab-confirmed flu by about 42% compared to unvaccinated children [3]. But the confidence interval on that number is wide: the true value could be as low as 7% or as high as 64% [3]. The same study found the injected flu vaccine was only about 29% effective, and that result was not even statistically significant — it could mean the shot did nothing [3]. Both of these are one-season numbers, not long-term.

For side effects, the only prospective safety trial in the retrieval tested just 48 children with asthma and found no significant lung function drop [1]. That is a tiny sample. A passive surveillance study from the US covering about 2.5 million doses logged 460 adverse event reports (40 serious), including 7 possible anaphylaxis cases and 2 cases of Guillain-Barre syndrome [7]. Passive systems like VAERS catch maybe 1% of real events, and they cannot tell you whether the rate is higher than what happens naturally. The same study noted that 73 of the 460 reports involved people who should not have been vaccinated at all (outside age range or with contraindicated conditions) [7]. The flu mist is a live virus, and in a few animal experiments, whole inactivated flu vaccines worsened lung disease on later infection with a mismatched strain — live vaccines did not have that problem in pigs [5], but the question of whether repeated annual boosting could narrow or misdirect immunity is largely unstudied in children over multiple years.

My call: the flu mist probably reduces flu illness in the short term, but the long-term safety data on school-wide annual use in the UK does not exist in these records, and the side-effect rate in healthy children cannot be reliably estimated from the studies here.

Confidence: low, because the most informative study design (vaccinated versus unvaccinated over several years with full adverse event tracking) was not found.