Tone Bruun1, Beatriz Valcarcel Salamanca, Terese Bekkevold, Henrik Døllner, Moustafa Gibory, Ann Marit Gilje, Elisebet Haarr, Anne-Marte Bakken Kran, Truls M Leegaard, Britt Nakstad, Svein Arne Nordbø, Astrid Rojahn, Ketil Størdal, Elmira Flem. 1. From the Departments of Infection Control and Vaccines Infectious Disease Epidemiology and Modelling, Norwegian Institute of Public Health, Oslo Children's Department, St. Olavs University Hospital Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Trondheim Department of Virology, Norwegian Institute of Public Health, Oslo Department of Pediatrics Department of Medical Microbiology, Stavanger University Hospital, Stavanger Department of Microbiology, Oslo University Hospital, Oslo Department of Microbiology and Infection Control, Akershus University Hospital, Lørenskog Institute of Clinical Medicine-Campus Ahus, Division of Medicine and Laboratory Sciences, University of Oslo, Oslo Department of Medical Microbiology, St. Olavs University Hospital, Trondheim Department of Pediatrics, Oslo University Hospital, Oslo Department of Pediatrics, Østfold Hospital Trust, Fredrikstad, Norway.
Abstract
BACKGROUND: Use of rotavirus vaccines worldwide since 2006 has led to a significant impact on the burden of rotavirus disease. However, only a third of European countries have introduced rotavirus vaccination in their immunization programs. In October 2014, rotavirus vaccination was introduced for Norwegian infants under strict age restrictions. Exclusive use of the monovalent rotavirus vaccine (RV1) and high vaccination coverage from the beginning enabled evaluation of the impact of this vaccine during the first 4 years after introduction. METHODS: Prospective laboratory-based surveillance among children <5 years of age hospitalized for acute gastroenteritis at 5 Norwegian hospitals was used to assess the vaccine effectiveness of 2 vaccine doses against rotavirus hospitalization in a case-control study. We used community controls selected from the national population-based immunization registry, and test-negative controls recruited through hospital surveillance. We also assessed the vaccine impact by using time-series analysis of retrospectively collected registry data on acute gastroenteritis in primary and hospital care during 2009-2018. RESULTS: Vaccine effectiveness against rotavirus-confirmed hospitalization was 76% (95% confidence interval [CI]: 34%-91%) using test-negative controls, and 75% (95% CI: 44%-88%) using community controls. In the postvaccine period, acute gastroenteritis hospitalizations in children <5 years were reduced by 45% compared with the prevaccine years (adjusted incidence rate ratios 0.55; 95% CI: 0.49-0.61). Reduction in hospitalizations was also seen in cohorts not eligible for vaccination. Rates in primary care decreased to a lesser degree. CONCLUSIONS: Four years after introduction of rotavirus vaccination in the national childhood immunization program, we recorded a substantial reduction in the number of children hospitalized for acute gastroenteritis in Norway, attributable to a high vaccine effectiveness.
BACKGROUND: Use of rotavirus vaccines worldwide since 2006 has led to a significant impact on the burden of rotavirus disease. However, only a third of European countries have introduced rotavirus vaccination in their immunization programs. In October 2014, rotavirus vaccination was introduced for Norwegian infants under strict age restrictions. Exclusive use of the monovalent rotavirus vaccine (RV1) and high vaccination coverage from the beginning enabled evaluation of the impact of this vaccine during the first 4 years after introduction. METHODS: Prospective laboratory-based surveillance among children <5 years of age hospitalized for acute gastroenteritis at 5 Norwegian hospitals was used to assess the vaccine effectiveness of 2 vaccine doses against rotavirus hospitalization in a case-control study. We used community controls selected from the national population-based immunization registry, and test-negative controls recruited through hospital surveillance. We also assessed the vaccine impact by using time-series analysis of retrospectively collected registry data on acute gastroenteritis in primary and hospital care during 2009-2018. RESULTS: Vaccine effectiveness against rotavirus-confirmed hospitalization was 76% (95% confidence interval [CI]: 34%-91%) using test-negative controls, and 75% (95% CI: 44%-88%) using community controls. In the postvaccine period, acute gastroenteritis hospitalizations in children <5 years were reduced by 45% compared with the prevaccine years (adjusted incidence rate ratios 0.55; 95% CI: 0.49-0.61). Reduction in hospitalizations was also seen in cohorts not eligible for vaccination. Rates in primary care decreased to a lesser degree. CONCLUSIONS: Four years after introduction of rotavirus vaccination in the national childhood immunization program, we recorded a substantial reduction in the number of children hospitalized for acute gastroenteritis in Norway, attributable to a high vaccine effectiveness.