Underlying cardiopulmonary conditions as a risk factor for influenza and
respiratory syncytial virus infection among community-dwelling adults
aged ≥65 years in Thailand: Findings from a two-year prospective cohort
study
Abstract
Background: Adults with cardiopulmonary conditions are at increased risk
for complications from influenza and respiratory syncytial virus (RSV)
infection, but few data are available from middle-income countries.
Methods: Using data from a prospective cohort study of influenza vaccine
effectiveness among community-dwelling Thai adults aged ≥65 years, we
estimated and compared the incidence of influenza and RSV in those with
and without cardiopulmonary conditions. During May 2015-May 2017, older
adults in a rural province in Thailand were followed weekly with
year-round surveillance for acute respiratory illness (ARI), defined
broadly as new onset or worsening of cough with or without fever, and
hospitalized ARI. When ill, nasal self-swabs and/or nasopharyngeal swabs
were collected for reverse-transcription polymerase chain reaction
testing. We used Poisson regression to calculate incidence rate ratios
(IRR), adjusting for age, sex, past healthcare-seeking behavior, weekly
influenza activity, and influenza vaccination. Results: Overall, 3,220
adults with a median age of 71 years (IQR 68-76) were enrolled; 1,324
(41.1%) were male; and 313 (9.7%) had ≥1 underlying cardio-pulmonary
condition, most commonly chronic obstructive pulmonary disease (131;
41.2%) or asthma (73; 23.3%). Compared to those without, participants
with cardiopulmonary conditions had higher incidences of ARI, influenza,
and RSV (Adjusted IRR: 1.83, 95% CI 1.63-2.05; 1.84, 95% CI 1.05-3.23;
2.02, 95% CI 1.10-3.72, respectively). Conclusion: Our findings show
that older adults in rural Thailand with cardiopulmonary conditions have
increased rates of ARI, influenza, and RSV infections, and support
efforts to ensure this population has access to influenza vaccines and
other respiratory illness prevention measures.