To determine the effectiveness of influenza vaccination on acute respiratory illness (ARI) and on acute exacerbation of chronic obstructive pulmonary disease (AECOPD) during a 2-year study conducted prior to and after influenza vaccination in patients with chronic obstructive pulmonary disease (COPD).
Eighty-seven male patients with COPD were stratified on the basis of their forced expiratory volume in 1 s (FEV(1)) as having mild, moderate and severe COPD. These patients were evaluated for a total duration of 2 years; 1 year prior to vaccination and for a period of 1 year following influenza vaccination. The vaccine (split virion, inactivated) composed of A/New Caledonia/20/99 (H1N1); A/California/7/2004(H3N2) and B/Shanghai/361/2002 strains all with 15 mug of haemagglutinin in each 0.5 ml dose.
The number of episodes and severity of ARI and AECOPD, classified as outpatient treatment, hospitalisation and requirement of mechanical ventilation, for a period of 1 year before and 1 year after influenza vaccination were recorded.
The incidence of ARI and AECOPD was 28.6 per 100 person-years prior to vaccination and 9.7 per 100 person-years postvaccination [relative risk (RR) 0.33; p = 0.005). Among the exacerbations because of natural infections prior to vaccination the incidences were 16.12, 42.1 and 33.14 per 100 person-years in the patients with mild, moderate and severe COPD respectively. These were significantly lower following vaccination with the incidences being 6.5, 18.5 and 8.42 per 100 person-years in the same subgroup of patients. Vaccine effectiveness in patients with mild COPD was 60% RR, 0.4 (p = 0.26); in patients with moderate COPD was 60% RR, 0.4 (p = 0.56); and in patients with severe COPD was 75% RR, 0.25 (p = 0.02). The total number of outpatient visits and hospitalisations before vaccination was eight and 14, respectively for a duration of 1 year in the total 87 patients with COPD being studied which decreased significantly to four outpatient visits and four hospitalisations postvaccination (p = 0.02). The overall effectiveness of influenza vaccination was 67%.
Influenza vaccination is highly effective in the prevention of ARI. Maximum protection was found to be in patients with severe COPD. Influenza vaccination in patients is associated with fewer outpatient visits and fewer hospitalisations.