Does the flu shot even work?
Here is what the checked sources say. Each title links to the original.
Vaccines for preventing influenza in healthy adults
Cochrane reviewed 52 trials with over 80,000 healthy adults aged 16 to 65 (searches to December 2016; single-season trials run 1969 to 2009). In those trials the flu shot probably cut confirmed flu from 2.3% to 0.9% over a season, a 59% relative drop; 71 adults needed vaccinating to prevent one case. Flu-like illness fell from 21.5% to 18.1%, with absolute benefit varying across settings. Effects on hospital stays and days off work were small and low-certainty. One author disclosed past consulting for GSK and a Sanofi trial committee role.
Vaccines for preventing influenza in healthy children
This Cochrane review of 41 trials with over 200,000 children (searches to December 2016; single-season trials run 1984 to 2013) found that in children aged 2 to 16, inactivated flu shots reduced confirmed flu from 30% to 11% (high-certainty evidence), so about 5 children needed vaccinating to prevent one case. The live nasal vaccine cut flu from 18% to 4% in children 3 to 16. Risks varied between trials, hospital data were not available, and few trials included children under 2. One author disclosed past consulting for GSK and a Sanofi trial committee role.
Influenza Vaccine Effectiveness Against Pediatric Deaths: 2010-2014
Researchers looked at 358 lab-confirmed flu deaths in US children aged 6 months to 17 years from July 2010 to June 2014. Vaccination status was known for 291; 26% of them had been vaccinated, against about 48% coverage in national survey groups. That comparison linked vaccination to a 65% lower risk of flu death (95% CI 54% to 74%), and 51% (31% to 67%) in children with high-risk conditions. This is an observational comparison with population estimates, not a trial, and vaccination status was unknown for 67 deaths.