2613. Pediatric respiratory syncytial virus hospitalizations, 2017 to 2022, the Canadian Immunization Monitoring Program Active (IMPACT)

BACKGROUND: Respiratory syncytial virus (RSV) is a leading cause of pediatric hospitalizations. We aimed to describe the epidemiology and burden of RSV-associated hospitalizations among children in Canadian pediatric centers from 2017 to 2022, including changes during the COVID-19 pandemic. METHODS: We performed active surveillance for hospitalized children 0 to 16 years of age with laboratory confirmed RSV at 13 Canadian Immunization Monitoring Program Active (IMPACT) pediatric hospitals during 5 seasons (2017-18 to 2021-22). Proportions of RSV hospitalizations over all-cause hospitalizations over time, and intensive care unit (ICU) admissions, prolonged admissions (≥ 7-days) and mortality proportions were calculated, overall and by age groups and regions. RSV hospitalization-associated burden was compared for 2021-22 to the pre-pandemic period of 2017-18 to 2019-20. Seasonality was described using epidemic curves. RESULTS: Among 11,014 RSV-associated hospitalizations 6,035 (54.8%) were male and 5,488 (50%) were aged < 6 months. Overall, 2,594 (23.6%) were admitted to ICU, of which 60.8% were aged < 6 months old. The median hospital stay was 4 days (interquartile range: 2-6). The mean number of hospitalizations during the pre-pandemic seasons was 2,522. Only 58 cases were reported in 2020-21, followed by 3,170 in 2021-22. The proportion of RSV hospitalizations over all-cause hospitalizations rose from 3.2% pre-pandemic to 4.5% in 2021-22 (difference 1.3% [95%CI 0.8-1.8]; p=0.07 after multiplicity adjustment). One province, Quebec, had a significant increase in RSV-hospitalization proportion in 2021-22 (2.5 percentage points, 95%CI 1.7-3.2, adjusted p-value 0.045). Age, sex, ICU admission, prolonged length of stay(≥7-days) and mortality proportions did not change in 2021-22 compared to the pre-pandemic period. Interregional differences in RSV seasonality were accentuated in 2021-22. Weekly RSV-associated hospital admissions in children aged 0 to 16 years at IMPACT centers, 2017-2022, by season [Figure: see text] Monthly RSV-associated hospital admissions in children aged 0 to 16 years at IMPACT centers, 2017-2022, by province [Figure: see text] CONCLUSION: RSV hospitalization burden in Canadian pediatric hospitals is substantial, especially in infants aged < 6 months. Following a near absence in 2020-21, RSV hospitalizations increased in the 2021-22 season, but severity of illness remained similar to the pre-pandemic period. These data will aid planning of RSV prevention strategies. DISCLOSURES: Nirma K. Vadlamudi, MPH, PhD, Broadstreet HEOR: Personal fees outside of the submitted work Scott Halperin, MD, CanSino: Grant/Research Support|CanSino: served on ad hoc advisory board|GlaxoSmithKline: Grant/Research Support|GlaxoSmithKline: served on ad hoc advisory board|Merck: Grant/Research Support|Merck: served on ad hoc advisory board|Moderna: Grant/Research Support|Moderna: served on ad hoc advisory board|Pfizer,: Grant/Research Support|Pfizer,: served on ad hoc advisory board|Sanofi-Pasteur: Grant/Research Support|Sanofi-Pasteur: served on ad hoc advisory board|Seqirus: Grant/Research Support|Seqirus: served on ad hoc advisory board|VBI Vaccines: Grant/Research Support|VBI Vaccines: served on ad hoc advisory board Joanne M. Langley, MD, CanSino: Grant/Research Support|Entos: Grant/Research Support|GlaxoSmithKline: Grant/Research Support|Merck: Grant/Research Support|Moderna: Grant/Research Support|Pfizer: Grant/Research Support|Sanofi-Pasteur: Grant/Research Support|Seqirus: Grant/Research Support|Symvivo: Grant/Research Support|VBI Vaccines: Grant/Research Support Shaun Morris, MD, MPH, DTM&H, FRCPC, FAAP, GlaxoSmithKline: Honoraria|JNJ China: Honoraria|Merck: served on ad hoc advisory board|Pfizer: Grant/Research Support|Pfizer: served on ad-hoc advisory board|Sanofi-Pasteur: served on ad-hoc advisory board Jeffrey Pernica, MD, MSc, FRCPC, DTMH, MedImmune: Grant/Research Support|Merck: Grant/Research Support Manish Sadarangani, BM BCh, FRCPC, DPhil, GlaxoSmithKline: Grant/Research Support|Merck: Grant/Research Support|Moderna: Grant/Research Support|Pfizer: Grant/Research Support|Sanofi Pasteur: Grant/Research Support|Seqirus: Grant/Research Support|Symvivo: Grant/Research Support|VBI Vaccines: Grant/Research Support Jesse Papenburg, MD, AstraZeneca: Personal fees outside of the submitted work|MedImmune: Grant/Research Support|Merck: Grant/Research Support|Merck: Personal fees outside of the submitted work