Determinants of RSV epidemiology following suppression through pandemic contact restrictions

Mihaly Koltai*, Fabienne Krauer, David Hodgson, Edwin van Leeuwen, Marina Treskova-Schwarzbach, Mark Jit, Stefan Flasche

*Corresponding author for this work

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Abstract

Introduction: COVID-19 related non-pharmaceutical interventions (NPIs) led to a suppression of RSV circulation in winter 2020/21 in the UK and an off-season resurgence in Summer 2021. We explore how the parameters of RSV epidemiology shape the size and dynamics of post-suppression resurgence and what we can learn about them from the resurgence patterns observed so far. 

Methods: We developed an age-structured dynamic transmission model of RSV and sampled the parameters governing RSV seasonality, infection susceptibility and post-infection immunity, retaining simulations fitting the UK's pre-pandemic epidemiology by a set of global criteria consistent with likelihood calculations. From Spring 2020 to Summer 2021 we assumed a reduced contact frequency, returning to pre-pandemic levels from Spring 2021. We simulated transmission forwards until 2023 and evaluated the impact of the sampled parameters on the projected trajectories of RSV hospitalisations and compared these to the observed resurgence. 

Results: Simulations replicated an out-of-season resurgence of RSV in 2021. If unmitigated, paediatric RSV hospitalisation incidence in the 2021/22 season was projected to increase by 30–60% compared to pre-pandemic levels. The increase was larger if infection risk was primarily determined by immunity acquired from previous exposure rather than age-dependent factors, exceeding 90 % and 130 % in 1–2 and 2–5 year old children, respectively. Analysing the simulations replicating the observed early outbreak in 2021 in addition to pre-pandemic RSV data, we found they were characterised by weaker seasonal forcing, stronger age-dependence of infection susceptibility and higher baseline transmissibility. 

Conclusion: COVID-19 mitigation measures in the UK stopped RSV circulation in the 2020/21 season and generated immunity debt leading to an early off-season RSV epidemic in 2021. A stronger dependence of infection susceptibility on immunity from previous exposure increases the size of the resurgent season. The early onset of the RSV resurgence in 2021, its marginally increased size relative to previous seasons and its decline by January 2022 suggest a stronger dependence of infection susceptibility on age-related factors, as well as a weaker effect of seasonality and a higher baseline transmissibility. The pattern of resurgence has been complicated by contact levels still not back to pre-pandemic levels. Further fitting of RSV resurgence in multiple countries incorporating data on contact patterns will be needed to further narrow down these parameters and to better predict the pathogen's future trajectory, planning for a potential expansion of new immunisation products against RSV in the coming years.

Original languageEnglish
Article number100614
JournalEpidemics
Volume40
Early online date21 Jul 2022
DOIs
Publication statusPublished - Sept 2022

Bibliographical note

Funding Information: MK, FK and MTS were supported by Germany’s Innovation Fund of the Joint Federal Committee (grant number 01VSF18015). MJ was supported by the National Institute for Health Research Health Protection Research Unit (NIHR HPRU, UK) in Immunisation at LSHTM (NIHR200929), in partnership with the UKHSA. MJ and EvL were supported by the NIHR HPRU in Modelling and Health Economics at Imperial College and LSHTM (NIHR200908) and by the European Union’s Horizon 2020 research and innovation programme - project EpiPose (101003688). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the Department of Health and Social Services or the UKHSA. SF was supported by a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society (Grant number 208812/Z/17/Z). DH was supported by the National Institute for Health Research (NIHR; 1R01AI141534–01A1). The funders played no role in the design and conduct of the study.

Open Access: This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Publisher Copyright: © 2022 The Authors. Published by Elsevier B.V.

Citation: Mihaly Koltai, Fabienne Krauer, David Hodgson, Edwin van Leeuwen, Marina Treskova-Schwarzbach, Mark Jit, Stefan Flasche, Determinants of RSV epidemiology following suppression through pandemic contact restrictions, Epidemics, Volume 40, 2022, 100614, ISSN 1755-4365,
https://doi.org/10.1016/j.epidem.2022.100614.

DOI: https://doi.org/10.1016/j.epidem.2022.100614.

Keywords

  • Disease Dynamics
  • Epidemiology
  • Non-pharmaceutical interventions
  • RSV
  • Transmission modelling

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