Josephine van Dongen

1 General introduction 13 and/or congenital pathology) was studied in smaller trials for Rotarix and RotaTeq. Omenaca et al assessed Rotarix to be immunogenic in 228 stable premature infants. 50 The anti-rotavirus IgA seroconversion rate after two doses was 86% (95%CI 79;90%). Goveia et al proved efficacy of RotaTeq against rotavirus gastroenteritis in 153 healthy premature infants. 51 Clinical efficacy after three doses was 70% (95%CI 15;95%) against rotavirus (strain type G1-4) gastroenteritis of any severity. Both studies also repor t on safety; similar frequencies of adverse events after placebo versus rotavirus vaccination were described. Vaccine effectiveness Effectiveness studies examine the effects of vaccination on disease burden in a real-life setting. Overall, in high-income countries repor ts on vaccine effectiveness against severe rotavirus gas- troenteritis have been consistently high, more than 80% after a full course of one of the globally available vaccines. 52–54 However, these estimates are mainly from studies in healthy infants. Based on the reassuring results from phase III trials, effectiveness of rotavirus vaccines in infants with medical risk conditions (MRC), until now, was assumed to be similar.This was corroborated by studies demonstrating high levels of post-vaccination seroconversion among infants with intes- tinal failure, 55 and effectiveness among infants on the neonatal care unit, including those with gastrointestinal pathology. 56 Countries that implemented infant rotavirus vaccination generally make no distinction in their recommendation between healthy infants and those belonging to the medical risk group (except for severe combined immunodeficiency). 57,58 Both globally avail- able vaccines, RotaTeq and Rotarix, have been licenced for administration to premature infants (respectively, from 25 and 27 weeks of gestational age onwards). In European countries, that implemented rotavirus vaccination for all infants, a decrease in hospital admissions for rotavirus infections from 65 to 84% has been observed. 5 This impact of rotavirus vaccination on rotavirus hospitalizations has also been repor ted for all-cause acute gastroenteritis admissions albeit to a lesser extent. A 54-57% reduction in hospitalized all-cause acute gastroenteritis was repor ted for Finland, 59,60 a 53% reduction for England 61 and 33% in Belgium. 62 In addition, universal rotavirus vaccination provides a so-called herd effect. Herd effect is defined as ``the reduction of infection or disease in the unimmunised segment as a result of immunis- ing a propor tion of the population’’. 63 The achieved propor tion of immunity in a population, dependent on vaccine coverage and efficacy, can lead to a decrease in symptomatic disease cases among unvaccinated individuals. This indirect vaccine effectiveness can be measured by comparing the risk of rotavirus infection among unvaccinated subjects in populations with and without infant rotavirus vaccination.A meta-analysis indicated that the indirect vaccine effective- ness of universal rotavirus vaccination on rotavirus hospitalization was 48% (95%CI 39;55%) in children under five years of age. 64 Reduction of transmission by a strong decrease in rotavirus infections among vaccinated infants benefits neonates and infants below six weeks of age, who