Is it worth getting the flu jab

The short version: the flu shot probably reduces your risk of dying from any cause by a modest amount, but the evidence is weaker than you have been told, and the question is whether that benefit is worth the injection for you.

The evidence here is almost entirely observational, not from randomized trials. That matters because people who get flu shots are also more likely to take care of their health in other ways. The best study in this set that tried to correct for that bias found a 4.6% reduction in all-cause mortality during flu season among elderly Kaiser Permanente members [4]. That is a small effect, not the dramatic 50% reductions that unadjusted studies often report.

The strongest evidence for benefit comes from specific high-risk groups. A meta-analysis of six observational studies in people with diabetes found that flu vaccination was associated with about a 46% lower odds of death [1]. A large Australian study of pregnant women found that maternal vaccination was associated with a 34% lower risk of infant death in the first year of life [2]. A cluster-randomized trial in UK care homes found that vaccinating staff reduced resident deaths by about 5 per 100 during flu season [3]. These are real signals, but they come from populations that are already vulnerable.

The risk of serious harm is low but not zero. The 1976 swine flu vaccine caused about 10 extra cases of Guillain-Barré syndrome per million doses [7]. For modern flu vaccines, the risk is smaller: about 1 extra case per million doses [5, 6]. That is a real risk, but it is very small compared to the background rate of GBS from infections themselves.

What the evidence does not answer is whether a healthy adult or child benefits from annual flu shots. The studies that show the largest effects are in the elderly, the chronically ill, and institutionalized populations. For a healthy person, the absolute risk of dying from flu is already very low, and the vaccine's marginal benefit shrinks accordingly. The Cochrane reviews (not in this retrieval but well-documented) have consistently found that flu vaccines in healthy adults prevent about one case of lab-confirmed flu per 40 vaccinated, but do not clearly reduce hospitalization or death.

My call: for an elderly person or someone with chronic illness, the flu shot is probably worth it, though the benefit is smaller than advertised. For a healthy adult or child, the benefit is marginal and the decision should be personal, not mandated. Confidence: moderate for high-risk groups, low for healthy individuals.