Modelled estimates of hospitalisations attributable to respiratory syncytial virus and influenza in Australia, 2009-2017

Altered epidemiological patterns of Respiratory Syncytial Virus and influenza detections in a tropical Australian setting 2020 to 2023

BACKGROUND

We describe the recent temporal patterns of respiratory syncytial virus (RSV) and influenza virus detections in the Northern Territory (NT) of Australia, between 2020 and 2023.

METHODS

This retrospective analysis of patients presenting with respiratory diseases utilised a multiplex viral nucleic acid detection assay for RSV, influenza and SARS Cov2 (COVID-19) to determine the relative frequency of non-COVID-19 respiratory viral detections by age and month during the study period.

RESULTS

During this period of the NT COVID-19 epidemic, disruption of the usual annual wet season RSV outbreak patterns occurred, and the yearly influenza peak was absent for two annual cycles. Our data also reveals that 25% of RSV infections were occurring in patients greater than 40 years of age, compared to 32% of influenza infections presenting in the same period, documenting a greater burden of adult disease than previously documented in the NT.

CONCLUSIONS

Loss of non-COVID-19 viral seasonality and a substantial unrecognised RSV adult burden were noted. We will continue to monitor seasonality, and the RSV burden and this will help to target the populations benefiting from recently released RSV vaccine.

Estimates of Seasonal Influenza Burden That Could Be Averted by Improved Influenza Vaccines in the Australian Population Aged Under 65 Years, 2015-2019

BACKGROUND

The interpretation of relative vaccine effectiveness (rVE) of improved influenza vaccines is complex. Estimation of burden averted is useful to contextualise their potential impact across different seasons. For the population aged under 65 years in Australia, this study estimated the additional morbidity and mortality that could be averted using improved influenza vaccines.

METHODS

We used observed, season-specific (2015-2019) influenza notification and influenza-coded hospitalisation frequencies and published modelled estimates of influenza-associated hospitalisations and deaths that occurred under the prevailing influenza vaccination coverage scenario. After back-calculating to the estimated burden in the population without vaccination, we applied published standard influenza vaccine effectiveness and coverage estimates to calculate the burden potentially averted by standard and improved influenza vaccines. A plausible range of rVE values were used, assuming 50% coverage.

RESULTS

The percentage point difference in absolute vaccine effectiveness (VE) of an improved vaccine compared to a standard vaccine is directly proportional to its rVE and inversely proportional to the effectiveness of the standard vaccine. The incremental burden averted by an improved vaccine is a function of both its difference in absolute VE and the severity of the influenza season. Assuming an rVE of 15% with 50% coverage, the improved vaccine was estimated to additionally avert 1517 to 12,641 influenza notifications, 287 to 1311 influenza-coded hospitalisations and 9 to 33 modelled all-cause influenza deaths per year compared to the standard vaccine.

CONCLUSIONS

Improved vaccines can have substantial clinical and population impact, particularly when the effectiveness of standard vaccines is low, and burden is high.

Estimated Respiratory Syncytial Virus-Related Hospitalizations and Deaths Among Children and Adults in Spain, 2016-2019

INTRODUCTION

Respiratory syncytial virus (RSV) causes a substantial disease burden among infants. In older children and adults, incidence is underestimated due to nonspecific symptoms and limited standard-of-care testing. We aimed to estimate RSV-attributable hospitalizations and deaths in Spain during 2016-2019.

METHODS

Nationally representative hospitalization and mortality databases were obtained from the Ministry of Health and the National Statistical Office. A quasi-Poisson regression model was fitted to estimate the number of hospitalizations and deaths attributable to RSV as a function of periodic and aperiodic time trends and viral activity, while allowing for potential overdispersion.

RESULTS

In children, the RSV-attributable respiratory hospitalization incidence was highest among infants aged 0-5 months (3998-5453 cases/100,000 person-years, representing 72% of all respiratory hospitalizations) and decreased with age. In 2019, estimated rates in children 0-5, 6-11, 12-23 months and 6-17 years were approximately 1.3, 1.4, 1.5, and 6.5 times higher than those based on standard-of-care RSV-specific codes. In adults, the RSV-attributable cardiorespiratory hospitalization rate increased with age and was highest among persons ≥ 80 years (1325-1506 cases/100,000, 6.5% of all cardiorespiratory hospitalizations). In 2019, for persons aged 18-49, 50-59, 60-79, and ≥ 80 years, estimated rates were approximately 8, 6, 8, and 16 times higher than those based on standard-of-care RSV-specific codes. The RSV-attributable cardiorespiratory mortality rate was highest among ≥ 80 age group (126-150 deaths/100,000, 3.5-4.1% of all cardiorespiratory deaths), when reported mortality rate ranged between 0 and 0.5/100,000.

CONCLUSIONS

When accounting for under-ascertainment, estimated RSV-attributable hospitalizations were higher than those reported based on standard-of-care RSV-specific codes in all age groups but particularly among older children and older adults. Like other respiratory viruses, RSV contributes to both respiratory and cardiovascular complications. Efficacious RSV vaccines could have a high public health impact in these age and risk groups.

Disease burden attributable to respiratory syncytial virus outbreaks in long-term care

Background

Respiratory syncytial virus (RSV) disease burden is significant among children; however, RSV can also cause excess morbidity and mortality among older adults. Populations in long-term care homes (LTCHs) may be at greater risk of exposure and increased infection severity. The objectives of this article are to identify evidence regarding disease burden and outcome severity attributable to RSV outbreaks among residents and staff in LTCHs; and to highlight reported population and outbreak characteristics.

Methods

All types of evidence were eligible for inclusion. Data utilized by included studies was between the end of the 2010 H1N1 influenza pandemic and the beginning of the coronavirus disease 2019 (COVID-19) pandemic. Evidence from the following countries was considered: G7, the European Union, Australia and New Zealand. A total of 167 articles were identified; 58 full texts were analyzed and four sources of evidence were eligible for inclusion. Data related to population characteristics, outbreak type and resident and staff outcomes were manually charted.

Results

There is a paucity of evidence sources pertaining to RSV outbreak burden among residents and staff in LTCHs. Outbreak duration ranged from 13 to 21 days. For each outbreak, 4-7 residents had confirmed RSV infection. Attack rates ranged from 12% to 38%. A spectrum of disease attributable to RSV outbreaks in LTCHs was identified, ranging from mild cold-like symptoms to death.

Conclusion

Integration of RSV into existing respiratory pathogen surveillance programs is important to characterize susceptibility, transmissibility and virulence of RSV in at-risk populations. There is a need for public health organizations to publish the findings from outbreak investigations to provide evidence to inform RSV outbreak prevention and response in LTCH settings.