Introduction Influenza vaccination produces an adequate serological response in adults with cystic fibrosis (CF)1 and is a recommended part of routine CF care. There is little evidence to date, however, of a clinical benefit from influenza vaccination in this patient group. We compared prospectively the rate of influenza infection with vaccination status among 100 adults with CF over the 2010/2011 UK influenza season.
Methods 100 adults with CF were enrolled in a prospective observational study of respiratory viruses between December 2010 and March 2011. Sputum, nose- and throat-swabs for PCR-based virological analysis were sent every 2 months and additionally at onset of acute respiratory illness through to June 2011. Prior to enrolment, sputum was sent for virology at onset of pulmonary exacerbations as part of routine care. Details of influenza vaccination status were obtained from the CF centre's database and GP records. Previous infection with influenza A/H1N1 was determined from clinical records.
Results Patients had a median age of 28 years (range 18–62). 88% had received the 2010/2011 seasonal influenza vaccine (A/California/7/2009/H1N1, A/Perth/16/2009/H3N2 & B/Brisbane/60/2008). 44% of the cohort had received the 2009 monovalent swine-origin influenza A/H1N1 vaccine and 8 patients had previously had PCR-confirmed swine-origin influenza. Over the study period there were 10 cases of influenza: 5 influenza A/H1N1, 4 influenza B and 1 dual influenza A/B infection. Among patients who received the 2010/2011 seasonal vaccine, 9/88 (10.2%) suffered influenza compared with 1/12 (8.3%) of those who had not been vaccinated (OR 1.25; 95% CI 0.14 to 10.9). All 9/9 patients who developed influenza despite being vaccinated were homozygous for the F508del mutation compared with 43/79 (55.7%) of vaccinated patients who did not develop influenza (p=0.009). No significant difference was seen between these groups with regard to age, gender, BMI, lung function, diabetes mellitus or use of oral corticosteroids.
Conclusions Influenza vaccination may have limited clinical efficacy in adults with CF. The influence of CF genotype on susceptibility to influenza infection and response to vaccination requires further investigation.