Acute respiratory infection, influenza vaccination and airway reactivity in asthma

One of the characteristic features of asthma is its tendency to become exacerbated during acute infections of the respiratory tract. There are only a few studies on the relation between infection and the exacerbation of asthma in adult asthmatics. Epithelial damage and airway inflammation, leading to transient increase in bronchial reactivity, are believed to be some of the mechanisms whereby respiratory infections cause asthmatic exacerbations. A total of 150 patients with asthma were studied. Study I, which dealt with the effect of respiratory infections on the exacerbation of asthma, comprised 92 asthmatics. The patients evaluated the severity of their disease daily by recording a symptom score in a follow-up chart. Peak expiratory flow (PEF) was measured by the patients with a mini-Wright peak flow meter twice a day. In order to detect respiratory infections, the occurrence of fever, sore throat and symptoms of rhinitis were also recorded. The daily self-observation by the patients was augmented by monthly examinations by a physician and an interview by a nurse. In the course of study I, 253 episodes of exacerbation of asthma were observed in 67 of the 92 patients. 63 (25%) of these 253 exacerbations were found in association with symptomatic respiratory infection (SRI). The mean duration of exacerbations associated with SRI was 11.4 days, significantly longer than the mean duration of 8.1 days of the other exacerbations. A series of 39 patients were entered in study II concerning the effect of vaccination on airway conductance and respiratory symptoms, and 27 asthmatics were assigned to study III which dealt with bronchial reactivity after vaccination with killed influenza virus vaccine. Study IV (bronchial reactivity after influenza A infection) comprised 13 patients. 21 members of hospital staff, without a history of chest disease, participated in studies II and IV as healthy controls. The virus vaccines in studies II, III and IV were provided by the manufacturers. The subjects were seen by the investigators immediately before and 2, 3 and either 14 or 21 days after vaccination. The presence of respiratory symptoms was assessed at each visit. In order to detect changes in respiratory function after vaccination, Raw and ITGV were measured at each visit. The results were expressed as specific airway conductance (SGaw). In studies III and IV, airway reactivity to inhaled histamine before and after vaccination was also measured.(ABSTRACT TRUNCATED AT 400 WORDS)