The burden of influenza in England by age and clinical risk group: A statistical analysis to inform vaccine policy

101

BackgroundRespiratory syncytial virus (RSV) is a leading cause of hospital admission in young children. With several RSV vaccines candidates undergoing clinical trials, recent estimates of RSV burden are required to provide a baseline for vaccine impact studies.ObjectivesTo estimate the number of RSV‐associated hospital admissions in children aged <5 years in England over a 5‐year period from 2007 using ecological time series modelling of national hospital administrative data.Patients/MethodsMultiple linear regression modelling of weekly time series of laboratory surveillance data and Hospital Episode Statistics (HES) data was used to estimate the number of hospital admissions due to major respiratory pathogens including RSV in children <5 years of age in England from mid‐2007 to mid‐2012, stratified by age group (<6 months, 6‐11 months, 1‐4 years) and primary diagnosis: bronchiolitis, pneumonia, unspecified lower respiratory tract infection (LRTI), bronchitis and upper respiratory tract infection (URTI).ResultsOn average, 33 561 (95% confidence interval 30 429‐38 489) RSV‐associated hospital admissions in children <5 years of age occurred annually from 2007 to 2012. Average annual admission rates were 35.1 (95% CI: 32.9‐38.9) per 1000 children aged <1 year and 5.31 (95% CI: 4.5‐6.6) per 1000 children aged 1‐4 years. About 84% (95% CI: 81‐91%) of RSV‐associated admissions were for LRTI. The diagnosis‐specific burden of RSV‐associated admissions differed significantly by age group.Conclusions RSV remains a significant cause of hospital admissions in young children in England. Individual‐level analysis of RSV‐associated admissions is required to fully describe the burden by age and risk group and identify optimal prevention strategies.

Section: Discussioncontrasting

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Estimating the burden of respiratory syncytial virus (RSV) on respiratory hospital admissions in children less than five years of age in England, 2007‐2012

Reeves

Hardelid

Gilbert

et al. 2017

101

“…During the 6 studied influenza seasons, we found that, while children under the age of 15 years have the highest ILI and MCIC rates, the very young (0‐4 years) and the elderly exhibit the highest rates of severe influenza‐associated hospitalizations. This is consistent with previous studies showing that young children and adolescents have the highest rates of medically attended influenza,7, 12, 13, 14 while the highest hospitalization rates for influenza are observed among very young15 and persons aged ≥65 years 16. Previous exposure to influenza viruses, providing a partial immunity to the circulating viruses, and higher vaccine coverage than in other age‐groups,17, 18 could account for the lower ILI rates at the primary care level in the elderly population.…”

Section: Discussionsupporting

confidence: 93%

Estimating the burden of seasonal influenza in Spain from surveillance of mild and severe influenza disease, 2010‐2016

Oliva

Delgado-Sanz

Larrauri

2017

BackgroundEstimating the national burden of influenza disease is challenging. We aimed to estimate the disease burden of seasonal influenza in Spain, at the primary care and hospital level, over the 6 influenza seasons after 2009 pandemic.MethodsWe used data from the Spanish Influenza Sentinel Surveillance System to estimate weekly influenza rates and the number of influenza‐like illness (ILI) and mild confirmed influenza cases (MCIC). From the surveillance of severe hospitalized confirmed influenza cases (SHCIC), we obtained hospitalization rates and total number of SHCIC, intensive care unit (ICU) admissions and deaths in influenza hospitalized patients. We estimated both mild and severe influenza cases, overall, and by age‐group (<5, 5‐14, 15‐64, and ≥65 years).ResultsThe highest cumulative rates of MCIC were observed in <15 years (1395‐3155 cases/100 000 population in 5‐14 years) and the lowest in ≥65 years (141‐608 cases/100 000 population). SHCIC rates revealed a characteristic U‐shaped distribution, with annual average hospitalization rates of 16.5 and 18.9 SHCIC/100, 000 p in 0‐4 years, and ≥65 years, respectively. We estimated an annual average of 866 868 cases of ILI attended in primary care (55% were MCIC), 3616 SHCIC, 1232 ICU admissions, and 437 deaths in SHCIC. The percentage of ICU admission among SHCIC was highest at 15‐64 years (42%), while the hospitalization fatality rate ranged from 1% in 0‐4 years to 18% in ≥65 years.ConclusionsThe ongoing Spanish Influenza Surveillance System allowed obtaining crucial information regarding the impact of mild and severe influenza in Spain.

“…Surveillance systems that collect ILI data may estimate iMAILI by multiplying the proportion positive for influenza among ILI patients in virological surveillance by the number of ILI patients in the population 19. We could not use this approach because syndromic surveillance collects data on MAARI, whereas virological surveillance focusses on ILI patients.…”

Section: Discussionmentioning

confidence: 99%

Estimation of influenza‐attributable medically attended acute respiratory illness by influenza type/subtype and age, Germany, 2001/02–2014/15

Heiden

Buchholz

2016

BackgroundThe total burden of influenza in primary care is difficult to assess. The case definition of medically attended “acute respiratory infection” (MAARI) in the German physician sentinel is sensitive; however, it requires modelling techniques to derive estimates of disease attributable to influenza. We aimed to examine the impact of type/subtype and age.MethodsData on MAARI and virological results of respiratory samples (virological sentinel) were available from 2001/02 until 2014/15. We constructed a generalized additive regression model for the periodic baseline and the secular trend. The weekly number of influenza‐positive samples represented influenza activity. In a second step, we distributed the estimated influenza‐attributable MAARI (iMAARI) according to the distribution of types/subtypes in the virological sentinel.ResultsSeason‐specific iMAARI ranged from 0.7% to 8.9% of the population. Seasons with the strongest impact were dominated by A(H3), and iMAARI attack rate of the pandemic 2009 (A(H1)pdm09) was 4.9%. Regularly the two child age groups (0‐4 and 5‐14 years old) had the highest iMAARI attack rates reaching frequently levels up to 15%‐20%. Influenza B affected the age group of 5‐ to 14‐year‐old children substantially more than any other age group. Sensitivity analyses demonstrated both comparability and stability of the model.ConclusionWe constructed a model that is well suited to estimate the substantial impact of influenza on the primary care sector. A(H3) causes overall the greatest number of iMAARI, and influenza B has the greatest impact on school‐age children. The model may incorporate time series of other pathogens as they become available.