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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

BACKGROUND Globally, rotavirus (RV) is the leading cause of acute gastroenteritis (AGE) in young children under 5 years of age. Implementation of RV vaccination is expected to result in fewer cases of RV in the target population, but it is unknown if this also results in vaccine-induced virus strain replacement. Rotarix, a monovalent vaccine based on G1P[8] rotavirus, was introduced in Norway in the children's immunization programme in September 2014. The main aim of this study was to describe the diversity of rotavirus circulating pre and post introduction of RV vaccine in Norway and investigate changes in genotype distribution during the first four years after implementation. MATERIALS AND METHODS A total of 1108 samples were collected from children under 5 years enrolled with AGE from five large hospitals in Norway and were analyzed for RV by EIA. All positive results were genotyped by multiplex semi-nested RT-PCR for identification of G and P types. RESULTS In total, 487 of the 1108 (44%) samples, collected from the enrolled children, were positive for RV by EIA method which were further genotyped. G1P[8] was found to be the most common type of RV pre and post RV vaccine implementation followed by G9P[8]. There were neither geographical nor temporal differences in genotype dominance. Also, no apparent changes were shown in the genotype distribution in the post-vaccine era for years from 2015 to 2018. In 21.4% of the cases, vaccine strains were detected. CONCLUSION Continuous rotavirus genotype surveillance is vital for assessing the effect of a vaccine program and monitoring for any emergence of vaccine-escape strains. Genotyping is also necessary to detect vaccine strains to avoid reporting false positive cases of active rotavirus infection in newly vaccinated cases. This article is protected by copyright. All rights reserved.

Background Bulk stool specimens are traditionally used for rotavirus detection but may be challenging to obtain from young children. Immediate and easy sampling may however be required in different situations, such as outbreak investigation. Objectives We assessed the diagnostic performance of rectal swabs compared to bulk stools for the detection of rotavirus by Enzyme Immunoassay (EIA) and multiplex semi-nested reverse transcription PCR (semi-nested RT-PCR) in children recruited through active hospital-based surveillance of acute gastroenteritis in Norway. Study design We obtained 265 paired bulk stool and rectal swab specimens from children under 5 years of age hospitalized with acute gastroenteritis (AGE). Both types of specimens were analyzed for rotavirus by EIA and semi-nested RT-PCR. In addition, VP6-spesific real-time PCR was used to evaluate the detection performance in the two specimen types. Results Concordant results were obtained in 257 (97%) paired specimens by EIA and in 248 (94%) pairs by semi-nested RT-PCR. Results of VP6-specific real-time PCR obtained from 100 pairs of specimens showed concordance in 91% of the pairs. Sensitivity and specificity for rectal swab specimens were 95% and 100% by EIA; 95% and 92% by semi-nested RT-PCR, respectively. Conclusion Both EIA and semi-nested RT-PCR showed a high accuracy, and rectal swab specimens are appropriate for rotavirus diagnosis and may be used as an alternate specimen type when collection of bulk stool is not feasible. © 2017. This is the authors’ accepted and refereed manuscript to the article. Locked until 1.11.2018 due to copyright restrictions. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/