Frequency of Asthma Exacerbations and Upper Respiratory Tract Infections Among Adult with Asthma According to Vaccination Status

Objectives: Annual influenza vaccinations are recommended for patients with asthma to prevent against seasonal influenza and influenza-triggered asthma exacerbations. However, there is conflicting data as to the benefit of the influenza vaccine on the frequency of asthma exacerbations. Therefore, this study aimed to assess the effectiveness of the influenza vaccine in terms of reducing the frequency of asthma-related exacerbations and upper respiratory tract infections among adult patients with asthma. Methods: This retrospective cohort study was performed from January to December 2018 in Muscat Governorate, Oman. A total of 466 patients attending nine randomly selected primary health centres in Muscat Governorate were enrolled in the study and followed-up for one year post-vaccination. Results: Most patients were female (70.6%) and had moderate-persistent asthma (42.9%). Overall, there were 203 patients (43.6%) in the vaccinated group and 263 (56.4%) in the non-vaccinated group. A proportion of patients in each group had allergic rhinitis (28.6% and 25.5%, respectively). The frequency of upper respiratory tract infections over the one-year follow-up period was significant lower in the vaccinated group compared to the non-vaccinated group (37.9% versus 73%; relative risk [RR]: 2.299, 95% confidence interval [CI]: 1.834–2.882; P <0.001); however, there was no significant difference in terms of the frequency of asthma exacerbations (41.9% versus 45.2%; RR: 0.925, 95% CI: 0.750–1.141; P >0.050). Conclusion: The influenza vaccine significantly reduces the frequency of upper respiratory tract infections over the following year. However, it did not significantly reduce the frequency of asthma exacerbations among adult Omanis with asthma. Further studies are recommended to support the protective effect of the vaccine in this regard. Keywords: Influenza Vaccines; Immunization; Asthma; Upper Respiratory Tract Infections; Observational Study; Oman.