Forecasting severe respiratory disease hospitalizations using machine learning algorithms.

BACKGROUND: Forecasting models predicting trends in hospitalization rates have the potential to inform hospital management during seasonal epidemics of respiratory diseases and the associated surges caused by acute hospital admissions. Hospital bed requirements for elective surgery could be better planned if it were possible to foresee upcoming peaks in severe respiratory illness admissions. Forecasting models can also guide the use of intervention strategies to decrease the spread of respiratory pathogens and thus prevent local health system overload. In this study, we explore the capability of forecasting models to predict the number of hospital admissions in Auckland, New Zealand, within a three-week time horizon. Furthermore, we evaluate probabilistic forecasts and the impact on model performance when integrating laboratory data describing the circulation of respiratory viruses. METHODS: The dataset used for this exploration results from active hospital surveillance, in which the World Health Organization Severe Acute Respiratory Infection (SARI) case definition was consistently used. This research nurse-led surveillance has been implemented in two public hospitals in Auckland and provides a systematic laboratory testing of SARI patients for nine respiratory viruses, including influenza, respiratory syncytial virus, and rhinovirus. The forecasting strategies used comprise automatic machine learning, one of the most recent generative pre-trained transformers, and established artificial neural network algorithms capable of univariate and multivariate forecasting. RESULTS: We found that machine learning models compute more accurate forecasts in comparison to naïve seasonal models. Furthermore, we analyzed the impact of reducing the temporal resolution of forecasts, which decreased the model error of point forecasts and made probabilistic forecasting more reliable. An additional analysis that used the laboratory data revealed strong season-to-season variations in the incidence of respiratory viruses and how this correlates with total hospitalization cases. These variations could explain why it was not possible to improve forecasts by integrating this data. CONCLUSIONS: Active SARI surveillance and consistent data collection over time enable these data to be used to predict hospital bed utilization. These findings show the potential of machine learning as support for informing systems for proactive hospital management.

Severe Acute Respiratory Infection (SARI) due to Influenza in Post-COVID Resurgence: Disproportionate Impact on Older Maori and Pacific Peoples.

OBJECTIVE: Influenza reemerged after a 2020-2021 hiatus in 2022, but understanding the resurgence needs pre-COVID era surveillance. We compared age- and ethnicity-specific incidence of severe acute respiratory infection (SARI) from a hospital network in Auckland, New Zealand, in 2022 against a baseline, 2012-2019. METHODS: Annual and monthly influenza SARI incidence per 1000 persons by age and ethnic group between 2012 and 2022 was calculated using resident population as the denominator. The hospitals capture most severe illness of the resident population. RESULTS: Influenza SARI incidence was highest among <1 year olds (2.62; 95% CI: 1.84-3.61) during 2012-2019, lowest at 6-14 years, and did not significantly increase until 50-64 years (0.35; 95% CI: 0.27-0.45), reaching 1.19 (95% CI: 0.57-1.55) in those ≥75 years. In all age groups, incidence was at least threefold higher in Maori and Pacific Peoples. No influenza SARI was identified in 2020-2021. In 2022, despite an early peak, annual incidence (<65 years) was lower than baseline in all ethnic groups, but incidence (≥65 years) in Maori (2.06; 95% CI: 1.22-3.26) and Pacific (3.94; 95% CI: 2.97-5.13) peoples was higher in 2022 than most baseline years, whereas incidence in NMNP (0.22; 95% CI: 0.14-0.32) was lower than any baseline year. CONCLUSION: After no influenza 2020-2021, Auckland had an early, high, narrow peak in 2022. Stratification by age and ethnicity revealed striking discrepancies in incidence among Maori and Pacific adults over 65 years compared with NMNP adults, with implications for targeted vaccination strategies.

Spatial and temporal transmission dynamics of respiratory syncytial virus in New Zealand before and after the COVID-19 pandemic.

Human respiratory syncytial virus (RSV) is a major cause of acute respiratory infection. In 2020, RSV was effectively eliminated from the community in New Zealand due to non-pharmaceutical interventions (NPI) used to control the spread of COVID-19. However, in April 2021, following a brief quarantine-free travel agreement with Australia, there was a large-scale nationwide outbreak of RSV that led to reported cases more than five times higher, and hospitalisations more than three times higher, than the typical seasonal pattern. In this study, we generated 1,471 viral genomes of both RSV-A and RSV-B sampled between 2015 and 2022 from across New Zealand. Using a phylodynamics approach, we used these data to better understand RSV transmission patterns in New Zealand prior to 2020, and how RSV became re-established in the community following the relaxation of COVID-19 restrictions. We found that in 2021, there was a large epidemic of RSV in New Zealand that affected a broader age group range compared to the usual pattern of RSV infections. This epidemic was due to an increase in RSV importations, leading to several large genomic clusters of both RSV-A ON1 and RSV-B BA9 genotypes in New Zealand. However, while a number of importations were detected, there was also a major reduction in RSV genetic diversity compared to pre-pandemic seasonal outbreaks. These genomic clusters were temporally associated with the increase of migration in 2021 due to quarantine-free travel from Australia at the time. The closest genetic relatives to the New Zealand RSV genomes, when sampled, were viral genomes sampled in Australia during a large, off-season summer outbreak several months prior, rather than cryptic lineages that were sustained but not detected in New Zealand. These data reveal the impact of NPI used during the COVID-19 pandemic on other respiratory infections and highlight the important insights that can be gained from viral genomes.

Comparison of the Burden and Temporal Pattern of Hospitalisations Associated With Respiratory Syncytial Virus (RSV) Before and After COVID-19 in New Zealand.

BACKGROUND: Changes in the epidemiology of illnesses caused by respiratory syncytial virus (RSV) infection following the COVID-19 pandemic are reported. The New Zealand (NZ) COVID-19 situation was unique; RSV community transmission was eliminated with the 2020 border closure, with a rapid and large increase in hospitalizations following the relaxation of social isolation measures and the opening of an exclusive border with Australia. METHODS: This active population-based surveillance compared the age-specific incidence and seasonality of RSV-associated hospitalizations in Auckland, NZ, for 2 years before and after the 2020 border closures. Hospitalisation rates between years were compared by age, ethnicity (European/other, Maori, Pacific and Asian) and socioeconomic group (1 = least, 5 = most deprived). RESULTS: There was no RSV transmission in 2020. In all other years, hospitalisation rates were highest for people of Pacific versus other ethnic groups and for people living in the most deprived quintile of households. RSV hospitalisation rates were higher in 2021 and 2022 than in 2018-19. The epidemic peak was higher in 2021, but not 2022, and the duration was shorter than in 2018-19. In 2021, the increase in RSV hospitalisation rates was significant across all age, sex, ethnic and socioeconomic groups. In 2022, the increase in hospitalisation rates was only significant in one age (1- < 3 years), one ethnic (Asian) and one socioeconomic group (quintile 2). CONCLUSIONS: COVID pandemic responses altered RSV-related hospitalisation seasonal patterns. Atypical features of RSV hospitalisation epidemiology were the increase in rates in older children and young adults, which lessened in 2022. Despite these variations, RSV hospitalisations in NZ continue to disproportionately affect individuals of Pacific ethnicity and those living in more socioeconomically deprived households. Whilst future public health strategies focused on RSV disease mitigation need to consider the potential shifts in epidemiological patterns when the transmission is disrupted, these variances must be considered in the context of longer-standing patterns of unequal disease distribution.

Impact of the COVID-19 related border restrictions on influenza and other common respiratory viral infections in New Zealand.

BACKGROUND: New Zealand's (NZ) complete absence of community transmission of influenza and respiratory syncytial virus (RSV) after May 2020, likely due to COVID-19 elimination measures, provided a rare opportunity to assess the impact of border restrictions on common respiratory viral infections over the ensuing 2 years. METHODS: We collected the data from multiple surveillance systems, including hospital-based severe acute respiratory infection surveillance, SHIVERS-II, -III and -IV community cohorts for acute respiratory infection (ARI) surveillance, HealthStat sentinel general practice (GP) based influenza-like illness surveillance and SHIVERS-V sentinel GP-based ARI surveillance, SHIVERS-V traveller ARI surveillance and laboratory-based surveillance. We described the data on influenza, RSV and other respiratory viral infections in NZ before, during and after various stages of the COVID related border restrictions. RESULTS: We observed that border closure to most people, and mandatory government-managed isolation and quarantine on arrival for those allowed to enter, appeared to be effective in keeping influenza and RSV infections out of the NZ community. Border restrictions did not affect community transmission of other respiratory viruses such as rhinovirus and parainfluenza virus type-1. Partial border relaxations through quarantine-free travel with Australia and other countries were quickly followed by importation of RSV in 2021 and influenza in 2022. CONCLUSION: Our findings inform future pandemic preparedness and strategies to model and manage the impact of influenza and other respiratory viral threats.

Circulation of influenza and other respiratory viruses during the COVID-19 pandemic in Australia and New Zealand, 2020-2021.

Objective: Circulation patterns of influenza and other respiratory viruses have been globally disrupted since the emergence of coronavirus disease (COVID-19) and the introduction of public health and social measures (PHSMs) aimed at reducing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission. Methods: We reviewed respiratory virus laboratory data, Google mobility data and PHSMs in five geographically diverse regions in Australia and New Zealand. We also described respiratory virus activity from January 2017 to August 2021. Results: We observed a change in the prevalence of circulating respiratory viruses following the emergence of SARS-CoV-2 in early 2020. Influenza activity levels were very low in all regions, lower than those recorded in 2017-2019, with less than 1% of laboratory samples testing positive for influenza virus. In contrast, rates of human rhinovirus infection were increased. Respiratory syncytial virus (RSV) activity was delayed; however, once it returned, most regions experienced activity levels well above those seen in 2017-2019. The timing of the resurgence in the circulation of both rhinovirus and RSV differed within and between the two countries. Discussion: The findings of this study suggest that as domestic and international borders are opened up and other COVID-19 PHSMs are lifted, clinicians and public health professionals should be prepared for resurgences in influenza and other respiratory viruses. Recent patterns in RSV activity suggest that these resurgences in non-COVID-19 viruses have the potential to occur out of season and with increased impact.

Sensitivity and specificity of surveillance case definitions in detection of influenza and respiratory syncytial virus among hospitalized patients, New Zealand, 2012-2016.

BACKGROUND: The WHO is exploring the value of adding RSV testing to existing influenza surveillance systems to inform RSV control programs. We evaluate the usefulness of four commonly used influenza surveillance case-definitions for influenza and RSV surveillance. METHODS: SHIVERS, a multi-institutional collaboration, conducted surveillance for influenza and RSV in four New Zealand hospitals. Nurses reviewed admission logs, enrolled patients with suspected acute respiratory infections (ARI), and obtained nasopharyngeal swabs for RT-PCR. We compared the performance characteristics for identifying laboratory-confirmed influenza and RSV severe acute respiratory infection (SARI), defined as persons admitted with measured or reported fever and cough within 10 days of illness, to three other case definitions: 1. reported fever and cough or shortness of breath, 2. cough and shortness of breath, or 3. cough. RESULTS: During April-September 2012-2016, SHIVERS identified 16,055 admissions with ARI; of 6374 cases consented and tested for influenza or RSV, 5437 (85%) had SARI and 937 (15%) did not. SARI had the highest specificity in detecting influenza (40.6%) and RSV (40.8%) but the lowest sensitivity (influenza 78.8%, RSV 60.3%) among patients of all ages. Cough or shortness of breath had the highest sensitivity (influenza 99.3%, RSV 99.9%) but the lowest specificity (influenza 1.6%, RSV 1.9%). SARI sensitivity among children aged <3 months was 60.8% for influenza and 43.6% for RSV-both lower than in other age groups. CONCLUSIONS: While SARI had the highest specificity, its sensitivity was limited, especially among children aged <3 months. Cough or shortness of breath was the most sensitive.

Modelling the impact of respiratory syncytial virus (RSV) vaccine and immunoprophylaxis strategies in New Zealand.

BACKGROUND: Mathematical models of respiratory syncytial virus (RSV) transmission can help describe seasonal epidemics and assess the impact of potential vaccines and immunoprophylaxis with monoclonal antibodies (mAb). METHODS: We developed a deterministic, compartmental model for RSV transmission, which was fitted to population-based RSV hospital surveillance data from Auckland, New Zealand. The model simulated the introduction of either a maternal vaccine or a seasonal mAb among infants aged less than 6 months and estimated the reduction in RSV hospitalizations for a range of effectiveness and coverage values. RESULTS: The model accurately reproduced the annual seasonality of RSV epidemics in Auckland. We found that a maternal vaccine with effectiveness of 30-40% in the first 90 days and 15-20% for the next 90 days could reduce RSV hospitalizations by 18-24% in children younger than 3 months, by 11-14% in children aged 3-5 months, and by 2-3% in children aged 6-23 months. A seasonal infant mAb with 40-60% effectiveness for 150 days could reduce RSV hospitalizations by 30-43%, 34-48% and by 14-21% in children aged 0-2 months, 3-5 months and 6-23 months, respectively. CONCLUSIONS: Our results suggest that either a maternal RSV vaccine or mAb would effectively reduce RSV hospitalization disease burden in New Zealand. Overall, a seasonal mAb resulted in a larger disease prevention impact than a maternal vaccine.

Impact of the COVID-19 nonpharmaceutical interventions on influenza and other respiratory viral infections in New Zealand.

Stringent nonpharmaceutical interventions (NPIs) such as lockdowns and border closures are not currently recommended for pandemic influenza control. New Zealand used these NPIs to eliminate coronavirus disease 2019 during its first wave. Using multiple surveillance systems, we observed a parallel and unprecedented reduction of influenza and other respiratory viral infections in 2020. This finding supports the use of these NPIs for controlling pandemic influenza and other severe respiratory viral threats.

Impact of oral corticosteroids on respiratory outcomes in acute preschool wheeze: a randomised clinical trial.

OBJECTIVE: To determine if administration of oral prednisolone to preschool children with acute wheeze alters respiratory outcomes. DESIGN: Double-blind, randomised, placebo-controlled equivalence trial. SETTING: Three hospitals in New Zealand. PATIENTS: 477 children aged 24-59 months with acute wheeze associated with respiratory illness. INTERVENTIONS: 2 mg/kg (maximum 40 mg) oral prednisolone or similar placebo, once daily for 3 days. MAIN OUTCOME MEASURES: Primary outcome was change in Preschool Respiratory Assessment Measure (PRAM) score 24 hours after intervention. Secondary outcomes included PRAM score at 4 hours, length of emergency department and inpatient stays, admission and representation rates, time to return to normal activities and use of additional oral prednisolone or intravenous medications. Analysis was by intention-to-treat. RESULTS: There was no difference between groups for change in PRAM score at 24 hours (difference between means -0.39, 95% CI -0.84 to 0.06, p=0.09). Absolute PRAM score was lower in the prednisolone group at 4 hours (median (IQR) 1 (0-2) vs 2 (0-3), p=0.01) and 24 hours (0 (0-1) vs 0 (0-1), p=0.01), when symptoms had resolved for most children regardless of initial treatment. Admission rate, requirement for additional oral prednisolone and use of intravenous medication were lower in the prednisolone group, although there were no differences between groups for time taken to return to normal activities or rates of representation within 7 days. CONCLUSION: Oral prednisolone does not alter respiratory outcomes at 24 hours or beyond in preschool children presenting with acute wheeze.

Respiratory Syncytial Virus-Associated Hospitalizations Among Adults With Chronic Medical Conditions.

BACKGROUND: In contrast with respiratory disease caused by influenza, information on the risk of respiratory syncytial virus (RSV) disease among adults with chronic medical conditions (CMCs) is limited. METHODS: We linked population-based surveillance of acute respiratory illness hospitalizations to national administrative data to estimate seasonal RSV hospitalization rates among adults aged 18-80 years with the following preexisting CMCs: chronic obstructive pulmonary disease (COPD), asthma, congestive heart failure (CHF), coronary artery disease (CAD), cerebrovascular accidents (CVA), diabetes mellitus (DM), and end-stage renal disease (ESRD). Age- and ethnicity-adjusted rates stratified by age group were estimated. RESULTS: Among 883 999 adult residents aged 18-80 years, 281 RSV-positive hospitalizations were detected during 2012-2015 winter seasons. Across all ages, RSV hospitalization rates were significantly higher among adults with COPD, asthma, CHF, and CAD compared with those without each corresponding condition. RSV hospitalization rates were significantly higher among adults with ESRD aged 50-64 years and adults with DM aged 18-49 years and 65-80 years compared with adults in each age group without these conditions. No increased risk was seen for adults with CVA. The CMC with the highest risk of RSV hospitalization was CHF (incidence rate ratio [IRR] range, 4.6-36.5 across age strata) and COPD (IRR range, 9.6-9.7). Among RSV-positive adults, CHF and COPD were independently associated with increased length of hospital stay. CONCLUSIONS: Adults with specific CMCs are at increased risk of RSV hospitalizations. Age affects this relationship for some CMCs. Such populations maybe relevant for future RSV prevention strategies.

COVID-19 and Infant Hospitalizations for Seasonal Respiratory Virus Infections, New Zealand, 2020.

In March 2020, a national elimination strategy for coronavirus disease was introduced in New Zealand. Since then, hospitalizations for lower respiratory tract infection among infants <2 years of age and cases of respiratory syncytial or influenza virus infection have dramatically decreased. These findings indicate additional benefits of coronavirus disease control strategies.

Impact of the COVID-19 nonpharmaceutical interventions on influenza and other respiratory viral infections in New Zealand.

Stringent nonpharmaceutical interventions (NPIs) such as lockdowns and border closures are not currently recommended for pandemic influenza control. New Zealand used these NPIs to eliminate coronavirus disease 2019 during its first wave. Using multiple surveillance systems, we observed a parallel and unprecedented reduction of influenza and other respiratory viral infections in 2020. This finding supports the use of these NPIs for controlling pandemic influenza and other severe respiratory viral threats.

Respiratory Health of Pacific Youth: An Observational Study of Associated Risk and Protective Factors Throughout Childhood.

BACKGROUND: Respiratory disease is the third most common cause of death in New Zealand, with Pacific people living in New Zealand bearing the greatest burden of this type of disease. Although some epidemiological outcomes are known, we lack the specifics required to formulate targeted and effective public health interventions. The Pacific Islands Families (PIF) birth cohort study is a study that provides a unique source of data to assess lung function and current respiratory health among participants entering early adulthood and to examine associations with early life events during critical periods of growth. OBJECTIVE: This paper aims to provide an overview of the design, methods, and scope of the Respiratory Health of Pacific Youth Study, which uses the overall PIF study cohort aged 18-19 years. METHODS: From 2000-2019, the PIF study has followed, from birth, the growth, and the development of 1398 Pacific children born in Auckland, New Zealand. Participants were nested within the overall PIF study (at ages 18-19 years) from June 2018, and assessments were undertaken until mid-November 2019. The assessments included respiratory and general medical histories, a general physical examination, assessment of lung function (forced expiratory volume and forced vital capacity), self-completed questionnaires (St George's Respiratory Questionnaire, European Quality of Life 5 Dimensions-3 Level, Epworth Sleepiness Scale for Children and Adolescents, and Leicester Cough Questionnaire), blood tests (eosinophils, Immunoglobulin E, Immunoglobulin G, Immunoglobulin A, Immunoglobulin M, and C-reactive protein), and chest x-rays. Noninferential analyses will be carried out on dimensionally reduced risk and protective factors and confounders. RESULTS: Data collection began in June 2018 and ended in November 2019, with a total of 466 participants recruited for submission of the paper. Collection and collation of chest x-ray data is still underway, and data analysis and expected results will be published by November 2020. CONCLUSIONS: This is the first longitudinal observational study to address the burden of respiratory disease among Pacific youth by determining factors in early life that impose long-term detriments in lung function and are associated with the presence of respiratory illness. Identifying risk factors and the magnitude of their effects will help in adopting preventative measures, establishing whether any avoidable risks can be modified by later resilient behaviors, and provide baseline measurements for the development of respiratory disease in later adult life. The study results can be translated into practice guidelines and inform health strategies with immediate national and international impact. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/18916.

Respiratory Syncytial Virus Vaccination during Pregnancy and Effects in Infants.

BACKGROUND: Respiratory syncytial virus (RSV) is the dominant cause of severe lower respiratory tract infection in infants, with the most severe cases concentrated among younger infants. METHODS: Healthy pregnant women, at 28 weeks 0 days through 36 weeks 0 days of gestation, with an expected delivery date near the start of the RSV season, were randomly assigned in an overall ratio of approximately 2:1 to receive a single intramuscular dose of RSV fusion (F) protein nanoparticle vaccine or placebo. Infants were followed for 180 days to assess outcomes related to lower respiratory tract infection and for 364 days to assess safety. The primary end point was RSV-associated, medically significant lower respiratory tract infection up to 90 days of life, and the primary analysis of vaccine efficacy against the primary end point was performed in the per-protocol population of infants (prespecified criterion for success, lower bound of the 97.52% confidence interval [CI] of ≥30%). RESULTS: A total of 4636 women underwent randomization, and there were 4579 live births. During the first 90 days of life, the percentage of infants with RSV-associated, medically significant lower respiratory tract infection was 1.5% in the vaccine group and 2.4% in the placebo group (vaccine efficacy, 39.4%; 97.52% CI, -1.0 to 63.7; 95% CI, 5.3 to 61.2). The corresponding percentages for RSV-associated lower respiratory tract infection with severe hypoxemia were 0.5% and 1.0% (vaccine efficacy, 48.3%; 95% CI, -8.2 to 75.3), and the percentages for hospitalization for RSV-associated lower respiratory tract infection were 2.1% and 3.7% (vaccine efficacy, 44.4%; 95% CI, 19.6 to 61.5). Local injection-site reactions among the women were more common with vaccine than with placebo (40.7% vs. 9.9%), but the percentages of participants who had other adverse events were similar in the two groups. CONCLUSIONS: RSV F protein nanoparticle vaccination in pregnant women did not meet the prespecified success criterion for efficacy against RSV-associated, medically significant lower respiratory tract infection in infants up to 90 days of life. The suggestion of a possible benefit with respect to other end-point events involving RSV-associated respiratory disease in infants warrants further study. (Funded by Novavax and the Bill and Melinda Gates Foundation; ClinicalTrials.gov NCT02624947.).

Respiratory Virus-related Emergency Department Visits and Hospitalizations Among Infants in New Zealand.

BACKGROUND: Estimates of the contribution of respiratory viruses to emergency department (ED) utilization remain limited. METHODS: We conducted surveillance of infants with acute respiratory infection (ARI) associated ED visits, which then resulted in either hospital admission or discharge home. Seasonal rates of specific viruses stratified by age, ethnicity, and socioeconomic status were estimated for both visits discharged directly from ED and hospitalizations using rates of positivity for each virus. RESULTS: During the 2014-2016 winter seasons, 3585 (66%) of the 5412 ARI ED visits were discharged home directly and 1827 (34%) were admitted to hospital. Among visits tested for all respiratory viruses, 601/1111 (54.1%) of ED-only and 639/870 (73.4%) of the hospital-admission groups were positive for at least one respiratory virus. Overall, respiratory virus-associated ED visit rates were almost twice as high as hospitalizations. Respiratory syncytial virus was associated with the highest ED (34.4 per 1000) and hospitalization rates (24.6 per 1000) among infants. ED visit and hospitalization rates varied significantly by age and virus. Maori and Pacific children had significantly higher ED visit and hospitalization rates for all viruses compared with children of other ethnicities. CONCLUSIONS: Many infants with acute respiratory virus infections are managed in the ED rather than admitted to the hospital. Higher rates of ED-only versus admitted acute respiratory virus infections occur among infants living in lower socioeconomic households, older infants and infants of Maori or Pacific versus European ethnicity. Respiratory virus infections resulting in ED visits should be included in measurements of ARI disease burden.

The health and economic burden of respiratory syncytial virus associated hospitalizations in adults.

BACKGROUND: Respiratory syncytial virus (RSV) is increasingly recognized as an important cause of illness in adults; however, data on RSV disease and economic burden in this age group remain limited. We aimed to provide comprehensive estimates of RSV disease burden among adults aged ≥18 years. METHODS: During 2012-2015, population-based, active surveillance of acute respiratory infection (ARI) hospitalizations enabled estimation of the seasonal incidence of RSV hospitalizations and direct health costs in adults aged ≥18 years in Auckland, New Zealand. RESULTS: Of 4,600 ARI hospitalizations tested for RSV, 348 (7.6%) were RSV positive. The median (interquartile range) length of hospital stay for RSV positive patients was 4 (2-6) days. The seasonal incidence rate (IR) of RSV hospitalizations, corrected for non-testing, was 23.6 (95% confidence intervals [CI] 21.0-26.1) per 100,000 adults aged ≥18 years. Hospitalization risk increased with age with the highest incidence among adults aged ≥80 years (IR 190.8 per 100,000, 95% CI 137.6-244.0). Being of Maori or Pacific ethnicity or living in a neighborhood with low socioeconomic status (SES) were independently associated with increased RSV hospitalization rates. We estimate RSV-associated hospitalizations among adults aged ≥18 years to cost on average NZD $4,758 per event. CONCLUSIONS: RSV infection is associated with considerable disease and economic cost in adults. RSV disproportionally affects adult sub-groups defined by age, ethnicity, and neighborhood SES. An effective RSV vaccine or RSV treatment may offer benefits for older adults.