Clinical Summary

Influenza vaccine is 55% effective in people with asthma

Takeaway

Despite perceptions to the contrary, seasonal influenza vaccine is overall 55% effective in a nationwide study of children and adults with asthma.
Vaccine effectiveness varies by season, strain, and age group.

Why this matters

Influenza infection is a major trigger for asthma attacks, but uptake of the vaccine is low among people with asthma.

Study design

Test-negative case-control study comparing 5022 vaccinated patients with asthma in Scotland (seasons 2010/11-2015/16), yielding 1,830,772 patient-years of data.
Cases tested positive for laboratory-confirmed influenza (exposed group) vs controls testing negative for laboratory-confirmed influenza (unexposed group).
Vaccine effectiveness (VE)=(1−adjusted OR) × 100.
Funding: Scottish Government; National Institute for Health Research.

Key results

Overall VE was 55.0%; 95% CI, 45.8%-62.7%.
VE varied by season:
- Highest VE: 76.1%; 95% CI, 55.6%-87.1% in season 2010/11 in which the A(H1N1) strain predominated and there was a good antigenic match between vaccine and strain.
VE varied by strain:
- Highest VE: A(H1N1) (70.7%; 95% CI, 32.5%-87.3% in season 2010/11) and B strains (83.2%; 95% CI, 44.3%-94.9%) in season 2010/11.
- Lowest VE: A(H3N2) (26.4%;95% CI, −12.0% to 51.6%) in season 2014/15.
VE varied by age:
- Highest VE against all viral strains: adults aged 18-54 years (57.0%; 95% CI, 42.3%-68.0%).

Limitations

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