Comparison of incidence and cost of influenza between healthy and high-risk children <60 months old in Thailand, 2011-2015

Abstract

IntroductionThailand recommends influenza vaccination for children aged 6 months to <36 months, but investment in vaccine purchase is limited. To inform policy decision with respect to influenza disease burden and associated cost in young children and to support the continued inclusion of children as the recommended group for influenza vaccination, we conducted a prospective cohort study of children in Bangkok hospital to estimate and compare influenza incidence and cost between healthy and high-risk children.MethodsCaregivers of healthy children and children with medical conditions (‘high-risk’) aged <36 months were called weekly for two years to identify acute respiratory illness (ARI) episodes and collect illness-associated costs. Children with ARI were tested for influenza viruses by polymerase chain reaction. Illnesses were categorized as mild or severe depending on whether children were hospitalized. Population-averaged Poisson models were used to compare influenza incidence by risk group. Quantile regression was used to examine differences in the median illness expenses.ResultsDuring August 2011-September 2015, 659 healthy and 490 high-risk children were enrolled; median age was 10 months. Incidence of mild influenza-associated ARI was higher among healthy than high-risk children (incidence rate ratio [IRR]: 1.67; 95% confidence interval [CI]: 1.13–2.48). Incidence of severe influenza-associated ARI did not differ (IRR: 0.40; 95% CI: 0.11–1.38). The median cost per mild influenza-associated ARI episode was $22 among healthy and $25 among high-risk children (3–4% of monthly household income; difference in medians: -$1; 95% CI for difference in medians: -$9 to $6). The median cost per severe influenza-associated ARI episode was $232 among healthy and $318 among high-risk children (26–40% and 36–54% of monthly household income, respectively; difference in medians: 110; 95% CI for difference in medians: -$352 to $571).ConclusionsCompared to high-risk children, healthy children had higher incidence of mild influenza-associated ARI but not severe influenza-associated ARI. Costs of severe influenza-associated ARI were substantial. These findings support the benefit of annual influenza vaccination in reducing the burden of influenza and associated cost in young children.

Influenza virus seroincidence in a cohort of healthy and high-risk children enrolled in infancy, Bangkok, Thailand

“…In the PRICE study, which was a parental study of this work, we observed a higher incidence of influenza virus infection as determined by rRT-PCR in healthy children compared to highrisk children in the entire cohort (Kittikraisak et al, 2018). However, we did not observe a similar difference in a subset of very young children, possibly because of the small sample size.…”

“…Enrollment method and study procedures have been previously described (Kittikraisak et al, 2018;Kittikraisak et al, 2017). Briefly, a prospective cohort study (Pediatric Respiratory Infection Cohort Evaluation, the PRICE study) to determine influenza burden among children living in the Bangkok Metropolitan areas who sought care at QSNICH (for any cause except acute respiratory illness) was established in August 2011.…”

“…In this study, we measured seroconversion to influenza at six-month intervals over two years in a cohort of children, enrolled during the first six months of life, in Bangkok, Thailand, to calculate subtype-specific cumulative incidence of infection by age and compare incidence of influenza virus infection by health status. This study was part of a larger cohort study of respiratory infection in the pediatric population in Bangkok, Thailand (Kittikraisak et al, 2018).…”

Economic Burden of Influenza in Thailand: A Systematic Review

“…Total costs were not disaggregated in 4 studies (36%). 21,[23][24][25] Discounting of the costs was not performed in 7 studies (64%) but this was acceptable because discounting is not necessary when a study period is short. Nine studies (82%) had no sensitivity analysis of cost estimation; however, this was defensible as their study designs did not have assumptions on cost estimation or different cost scenarios.…”

Cost of Nine Pediatric Infectious Illnesses in Low- and Middle-Income Countries: A Systematic Review of Cost-of-Illness Studies

“…Particularly, we found two studies assessing the cost of measles in the Federated States of Micronesia [49] and the cost of measles and rubella in Romania [50] -a first for measles and rubella in LMIC. Other studies examined further the cost of GE [51][52][53][54][55][56][57][58][59], pneumonia [51,52,[59][60][61][62][63], and influenza [64,65]. Some of them generated COI estimates from a programmatic approach, evaluating the cost of treating diarrhea and pneumonia through an integrated community case management [51,52,59].…”