Does workplace flu vaccination reduce sick days? What the evidence says
What the largest independent review of flu vaccines in healthy adults found, and how to set realistic expectations for a workplace programme.
In short: good-quality evidence shows flu vaccination lowers the chance of healthy adults catching flu. The evidence that it measurably reduces days off work is weaker. The strongest case for a workplace clinic is protecting individual staff and making vaccination easy, rather than a guaranteed fall in absence figures.
Where does the best evidence come from?
The Cochrane review Vaccines for preventing influenza in healthy adults is the most comprehensive independent summary of the research. Its latest update, published in February 2018, pooled 52 clinical trials involving more than 80,000 adults. Cochrane reviews are produced independently of vaccine manufacturers and grade how certain each finding is.
What did it find?
| Outcome (inactivated vaccine) | Unvaccinated | Vaccinated | Certainty |
|---|---|---|---|
| Laboratory-confirmed flu | 2.3% | 0.9% | Moderate |
| Flu-like illness (any cause) | 21.5% | 18.1% | Moderate |
| Hospital admission | 14.7% | 14.1% | Low |
| Days off work | about 0.04 days fewer per person | Low | |
Put another way, the review estimated that 71 healthy adults need to be vaccinated to prevent one case of confirmed flu, and 29 to prevent one flu-like illness. Fever after vaccination rose slightly, from 1.5% to 2.3%, and the review found no evidence of a link between flu vaccination and serious adverse events.
Why is the absence finding so small?
Most people in these trials were young, healthy adults, and in many seasons only a small proportion of them caught flu at all. Days off work were measured in only some trials, and the review rated this evidence as low certainty. Low certainty means the true effect could be different; it does not show that vaccination has no effect on absence. Protection also varies from season to season depending on how well the vaccine matches the circulating strains.
What does this mean for an employer?
- Be accurate in staff messaging. Say that the vaccine reduces the chance of getting flu and that illness is likely to be milder if you do. Avoid promising that nobody will be off sick.
- Think about who benefits most. Staff aged 65 or over, those with long-term conditions, and those living with vulnerable people can usually get a free NHS vaccine. Pregnant colleagues should be pointed towards their NHS offer. A workplace clinic mainly helps everyone else, who would otherwise pay privately or go without.
- Make it convenient. Uptake depends on access. An on-site clinic removes travel and waiting time.
- Measure what you can. Aggregate uptake figures, which HYL reports after every clinic, are a fair measure of how well the programme reached people.
Read the workplace flu business case · Tax treatment of staff flu jabs
Sources
- Demicheli V, Jefferson T, Ferroni E, Rivetti A, Di Pietrantonj C. Vaccines for preventing influenza in healthy adults. Cochrane Database of Systematic Reviews 2018
- Cochrane plain language summary: Vaccines to prevent influenza in healthy adults
- NHS: Flu vaccine
- UKHSA: Your guide to who’s eligible for the autumn 2026 flu vaccine
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