How effective are flu shots?

Turns out that they are not very effective.

The northern hemisphere is just entering summer so even the thought of discussing flu (influenza) vaccines seems a bit out of place. We are still a few months away from the flu shot marketing campaigns of various government agencies, employers, schools and neighbourhood pharmacies being kicked off. But the CBC recently ran an article about the effectiveness of the 2015-16 vaccine. Experts interviewed for this story believed that this vaccine was 40-45% effective – much better than the 2014-15 flu shot which which essential gave zero protection – but still not very good.

“The good news is the data are more reliable. But the bad news is that experts now realize the flu vaccine protects only about half of the time.”

In 2014, the Cochrane Collaboration published a meta analysis of 90 studies (randomized controlled trials and comparative studies on flu vaccines, covering the period from 1960-2013) that also showed a poor record of the vaccine’s effectiveness.

“The preventive effect of parenteral inactivated influenza vaccine on healthy adults is small: at least 40 people would need vaccination to avoid one ILI (Influenza like illness) case (95% confidence interval (CI) 26 to 128) and 71 people would need vaccination to prevent one case of influenza (95% CI 64 to 80). Vaccination shows no appreciable effect on working days lost or hospitalisation.

The protection against ILI that is given by the administration of inactivated influenza vaccine to pregnant women is uncertain or at least very limited; the effect on their newborns is not statistically significant.

The effectiveness of live aerosol vaccines on healthy adults is similar to inactivated vaccines: 46 people (95% CI 29 to 115) would need immunisation to avoid one ILI case.”

Keeping germs at bay by following general cleanliness habits (wash your hands before touching eyes, nose, mouth; clean common surfaces; don’t sneeze at people) and eating a healthy diet (which includes fruits, vegetables and drinking  plenty of water) are probably still the best flu prevention tips.

Stay away from germs to prevent the flu