Group A rotaviruses in children with gastroenteritis in a Canadian pediatric hospital: The prevaccine era

Impact of a publicly funded monovalent rotavirus vaccination program in the Province of Quebec (Canada)

In November 2011, the province of Quebec, Canada implemented a publicly funded rotavirus (RV) vaccination program using the monovalent RV vaccine (RV1). To assess its impact, trends in passive RV laboratory detection and Emergency Department (ED) visits for gastroenteritis (GE) at two pediatric centers were evaluated.

METHODS

RV tests performed were extracted from the virology laboratory databases and ED visits for GE between July 1, 2006 and June 30, 2013, from the ED databases of The Montreal Children's Hospital (MCH) and Centre Hospitalier Universitaire de Sherbrooke (CHUS). The percent positive RV tests over time and season duration were assessed using 5-week moving averages. We defined season start and end as the first two and the last two consecutive weeks where the percent positive RV tests were ≥ 10%, respectively.

RESULTS

Comparing the pre- and post-vaccination program periods, a decrease in the proportion of positive RV tests was seen: 15.9% vs. 5.1% (p<0.001). Pre-vaccination program, RV seasons started between December and February, peaked in March or April and ended in May. In 2011-2012, the season started in March, peaked in April, and ended in May. In 2012-2013, the season lasted 3 weeks in May. ED visits for GE decreased post-introduction of the RV1 program: from 4.8% to 3.4% in 2011-2012, and 4.2% in 2012-13 (p<0.001). In children <2 years of age, ED GE visits decreased from 7.5% to 4.8% in 2011-2012, and 5.2% in 2012-2013 (p<0.001). Admissions for GE also decreased significantly from 0.41% of all ED visits to 0.14% in 2011-2012 and 0.22% in 2012-2013 (p<0.005).

CONCLUSION

Implementation of a publicly funded RV vaccination program had a major impact on the epidemiology of RV infections in Quebec: RV seasons have started later and been of shorter duration, peak positives were fewer, and ED visits for GE decreased.

Review of global rotavirus strain prevalence data from six years post vaccine licensure surveillance: is there evidence of strain selection from vaccine pressure?

Comprehensive reviews of pre licensure rotavirus strain prevalence data indicated the global importance of six rotavirus genotypes, G1P[8], G2P[4], G3P[8], G4P[8], G9P[8] and G12P[8]. Since 2006, two vaccines, the monovalent Rotarix (RV1) and the pentavalent RotaTeq (RV5) have been available in over 100 countries worldwide. Of these, 60 countries have already introduced either RV1 or RV5 in their national immunization programs. Post licensure vaccine effectiveness is closely monitored worldwide. This review aimed at describing the global changes in rotavirus strain prevalence over time. The genotype distribution of the nearly 47,000 strains that were characterized during 2007-2012 showed similar picture to that seen in the preceding period. An intriguing finding was the transient predominance of heterotypic strains, mainly in countries using RV1. Unusual and novel antigen combinations continue to emerge, including some causing local outbreaks, even in vaccinated populations. In addition, vaccine strains have been found in both vaccinated infants and their contacts and there is evidence for genetic interaction between vaccine and wild-type strains. In conclusion, the post-vaccine introduction strain prevalence data do not show any consistent pattern indicative of selection pressure resulting from vaccine use, although the increased detection rate of heterotypic G2P[4] strains in some countries following RV1 vaccination is unusual and this issue requires further monitoring.