Image by National Institute of Allergy and Infectious Diseases via UnSplash
Image by National Institute of Allergy and Infectious Diseases via UnSplash

How NZ avoided a 'triple-demic' of RSV, COVID-19, and influenza

Embargoed until: Publicly released:
Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Observational study: A study in which the subject is observed to see if there is a relationship between two or more things (eg: the consumption of diet drinks and obesity). Observational studies cannot prove that one thing causes another, only that they are linked.

People: This is a study based on research using people.

Respiratory syncytial virus (RSV) transmission was eliminated for twelve months in New Zealand thanks to border-closures, social distancing and facemask use in 2020. When pandemic restrictions eased in 2021, RSV returned with a peak 16 times higher than pre-Covid levels in the high-risk infant age group - although the cases weren't more severe. Authors of the study say the high number of cases was due to an "immunity gap" from the year before. Since RSV returned to New Zealand before community transmission of Covid-19, we managed to avoid simultaneous peaks of Covid, flu and RSV, as seen in other countries.

Journal/conference: The Lancet Regional Health - Western Pacific

Research: Paper

Organisation/s: University of Auckland, ESR (Institute of Environmental Science and Research Ltd), Te Whatu Ora - Health New Zealand, University of Otago

Funder: Our grateful thanks to Flu Lab for funding the SHIVERS-V team’s research in NZ under “Influenza in a post-COVID world”, of which this project is a part.

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Dr David Broderick, Research Fellow, Faculty of Medical and Health Sciences, University of Auckland, comments;

Respiratory syncytial virus (RSV) is responsible for many respiratory hospital admissions in winter, particularly early in life. In Aotearoa New Zealand, measures taken in 2020 to eliminate COVID-19 also eliminated RSV transmission.

Our study looked at the impact of RSV return in 2021 and 2022. We found a sharp increase in weekly cases in 2021, with a peak 16 times the pre-COVID rate in the high-risk infant age group. However, a similar proportion of cases were admitted to ICU, suggesting no change in individual severity but a potentially overwhelming burden on the healthcare system. Consistent surveillance methodology makes it likely that these increases resulted from an RSV immunity gap.

In 2022, we saw reduced admissions and ICU admissions rates across most ages, possibly due to high circulating immunity from the 2021 season. This protection may have sheltered the health system from an overwhelming ‘triple-demic’ as seen in other nations where RSV, influenza and COVID-19 had coalescing peaks.

New Zealand does not have funded RSV immunisations routinely available for infants, as seen in Australia, Europe and the US/Canada. Such protection could provide more widespread immunity - as seen in 2022 - without intense waves of infection.

Last updated: 01 Nov 2024 11:39am
Declared conflicts of interest:
None declared.

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