Seasonal Influenza Vaccine Effectiveness in People With Asthma: A National Test-Negative Design Case-Control Study

Area of Science:

• Immunology
• Public Health
• Respiratory Medicine

Background:

• Influenza infections are known triggers for asthma exacerbations.
• Influenza vaccination is a potential preventive measure for people with asthma.
• Low vaccine uptake in this population is partly due to concerns about vaccine effectiveness.

Purpose of the Study:

• To estimate the effectiveness of influenza vaccination in people with asthma.
• To analyze vaccine effectiveness across multiple influenza seasons and strains.

Main Methods:

• A test-negative case-control study design was employed.
• Individual patient data from 223 practices in Scotland were analyzed over six seasons (2010/2011 to 2015/2016).
• Data included 1,830,772 patient-years linked with 5910 virological swabs.

Main Results:

• Influenza vaccination was associated with a 55.0% risk reduction in laboratory-confirmed influenza infections among people with asthma.
• Vaccine effectiveness varied by season, influenza strain (higher against A(H1N1) and B, lower against A(H3N2)), and age group.
• The highest effectiveness (76.1%) was observed in the 2010/2011 season with a good match to the dominant A(H1N1) strain.

Conclusions:

• Influenza vaccination provides meaningful protection against influenza in people with asthma.
• Strategies to increase influenza vaccine uptake could significantly reduce influenza-induced asthma attacks.