key: cord-0023162-72x08kpk
authors: Hatter, Lee; Eathorne, Allie; Hills, Thomas; Bruce, Pepa; Beasley, Richard
title: Respiratory syncytial virus: paying the immunity debt with interest
date: 2021-10-23
journal: Lancet Child Adolesc Health
DOI: 10.1016/s2352-4642(21)00333-3
sha: da4d1e6d40af0fd2ce86db00eb6fbc2c1ecfea65
doc_id: 23162
cord_uid: 72x08kpk

nan

Respiratory syncytial virus (RSV) results in seasonal winter epidemics and accounts for 60-80% of bronchio litis hospitalisations, the most common cause of admission to hospital for infants in high-income countries. Globally, rates of RSV infection and bronchiolitis have been remarkably low since early 2020. 1 The implementation of stringent public health non-pharmaco logical interventions targeting COVID-19 has been credited for this success. Nevertheless, concerns have been raised about the potential for more severe RSV epidemics in the future due to a so-called immunity debt, a term proposed to describe the paucity of protective immunity arising from extended periods of low exposure to a given pathogen, leaving a greater proportion of the population susceptible to the disease. 2 This immunity debt is a particular concern for RSV, for which temporary immunity is obtained through exposure to the virus and maternal antibodies wane quickly; without seasonal exposure, immunity decreases and susceptibility to future, and potentially more severe, infection increases.

New Zealand had very low levels of RSV infection in 2020, 3 with no seasonal epidemic of hospital admissions for bronchiolitis (figure). A partial relaxation of New Zealand's strict border closure policy in April, 2021, to allow quarantinefree travel between Australia and New Zealand, was followed by a rapid increase in RSV cases in New Zealand and hence an increase in admissions due to bronchiolitis. At the peak (week 28, 2021), RSV surveillance numbers were more than five times the 2015-19 peak average. 6,7 Provisional national data for children aged 0-4 years show that in 2021 there were 866 hospital discharges for bronchiolitis during week 27 (bronchiolitis peak); an incidence rate of 284 per 100 000 children in this age group, which was three times higher than the average of peaks in 2015-19. A similar increase was seen in intensive care unit (ICU) discharges for bronchiolitis, with an incidence rate of 15 per 100 000 children aged 0-4 years, which was 2·8 times higher than the average of peaks in 2015-19. These similar rate increases in hospitalisation and ICU discharges suggest that although there was more disease, it was not more severe than in previous years.

Despite New Zealand being largely free of COVID-19 and influenzawith only one hospitalisation and no ICU admissions due to COVID-19 in children aged 0-4 years and no positive influenza isolates in any age group 8 as of week 29, 2021the pressure on the New Zealand health system due to bronchiolitis has been substantial. In countries with a higher COVID-19 burden, particularly those in the northern hemisphere that are entering their third winter since the start of this pandemic, the pressures resulting from RSV epidemics might be even greater than has been seen in New Zealand. Planning for preventive measures is needed now. Infection control measures, such as keeping infants and children with respiratory symptoms at home, will be required, and hospitals should prepare for increased numbers of admissions than historical data suggest. LH 

Pediatric Infectious Disease Group (GPIP) position paper on the immune debt of the COVID-19 pandemic in childhood, how can we fill the immunity gap?

What can we learn from our 2021 respiratory syncytial virus experience?

History of the COVID-19 alert system

Estimated resident population by age and sex

Public Health Surveillance inforamtion for New Zealands Public Health Action. Laboratory-based virology weekly report

COVID-19 border controls prevent a 2021 seasonal influenza epidemic in New Zealand