The evolving epidemiology of rotavirus gastroenteritis in central Portugal with modest vaccine coverage

Rotavirus genotype shifts among Swedish children and adults-Application of a real-time PCR genotyping

BACKGROUND

It is well known that human rotavirus group A is the most important cause of severe diarrhoea in infants and young children. Less is known about rotavirus infections in other age groups, and about how rotavirus genotypes change over time in different age groups.

OBJECTIVES

Develop a real-time PCR to easily genotype rotavirus strains in order to monitor the pattern of circulating genotypes.

STUDY DESIGN

In this study, rotavirus strains in clinical samples from children and adults in Western Sweden during 2010-2014 were retrospectively genotyped by using specific amplification of VP 4 and VP 7 genes with a new developed real-rime PCR.

RESULTS

A genotype was identified in 97% of 775 rotavirus strains. G1P[8] was the most common genotype representing 34.9%, followed by G2P[4] (28.3%), G9P[8] (11.5%), G3P[8] (8.1%), and G4P[8] (7.9%) The genotype distribution changed over time, from predominance of G1P[8] in 2010-2012 to predominance of G2P[4] in 2013-2014. There were also age-related differences, with G1P[8] being the most common genotype in children under 2 years (47.6%), and G2P[4] the most common in those over 70 years of age (46.1%.). The shift to G2P[4] in 2013-2014 was associated with a change in the age distribution, with a greater number of rotavirus positive cases in elderly than in children.

CONCLUSIONS

By using a new real-time PCR method for genotyping we found that genotype distribution was age related and changed over time with a decreasing proportion of G1P[8].

Human rotavirus strains circulating in Venezuela after vaccine introduction: predominance of G2P[4] and reemergence of G1P[8]

BACKGROUND

Rotavirus (RV) is the most common cause of severe childhood diarrhea worldwide. Despite Venezuela was among the first developing countries to introduce RV vaccines into their national immunization schedules, RV is still contributing to the burden of diarrhea. Concerns exist about the selective pressure that RV vaccines could exert on the predominant types and/or emergence of new strains.

RESULTS

To assess the impact of RV vaccines on the genotype distribution 1 year after the vaccination was implemented, a total of 912 fecal specimens, collected from children with acute gastroenteritis in Caracas from February 2007 to April 2008, were screened, of which 169 (18.5%) were confirmed to be RV positive by PAGE. Rotavirus-associated diarrhea occurred all year-round, although prevailed during the coolest and driest months among unvaccinated children under 24 months old. Of 165 RV strains genotyped for G (VP7) and P (VP4) by seminested multiplex RT-PCR, 77 (46.7%) were G2P[4] and 63 (38.2%) G1P[8]. G9P[8], G3P[8] and G2P[6] were found in a lower proportion (7.3%). Remarkable was also the detection of <5% of uncommon combinations (G8P[14], G8P[4], G1P[4] and G4P[4]) and 3.6% of mixed infections. A changing pattern of G/P-type distribution was observed during the season studied, with complete predominance of G2P[4] from February to June 2007 followed by its gradual decline and the reemergence of G1P[8], predominant since January 2008. Phylogenetic analysis of VP7 and VP4 genes revealed a high similarity among G2P[4] and global strains belonging to G2-II and P[4]-V lineages. The amino acid substitution 96D → N, related with reemergence of the G2 genotype elsewhere, was observed. The G1P[8] strains from Caracas were grouped into the lineages G1-I and P[8]-III, along with geographically remote G1P[8] rotaviruses, but they were rather distant from Rotarix® vaccine and pre-vaccine strains. Unique amino acid substitutions observed on neutralization domains of the VP7 sequence from Venezuelan post-vaccine G1P[8] could have conditioned their re-emergence and a more efficient dissemination into susceptible population.

CONCLUSIONS

The results suggest that natural fluctuations of genotypes in combination with forces driving the genetic evolution could determine the spread of novel strains, whose long-term effect on the efficacy of available vaccines should be determined.

Assessing the impacts of the first year of rotavirus vaccination in the United Kingdom

The United Kingdom (UK) added rotavirus (RV) vaccine (Rotarix GlaxoSmithKline) to the national vaccine schedule in July 2013. During the 2012–2014 rotavirus seasons, children presenting to the Bristol Royal Hospital for Children Emergency Department with gastroenteritis symptoms had stool virology analysis (real-time PCR) and clinical outcome recorded. Nosocomial cases were identified as patients with non-gastroenteritis diagnosis testing positive for rotavirus > 48h after admission. In comparison to average pre-vaccine seasons, in the first year after vaccine introduction there were 48% fewer attendances diagnosed with gastroenteritis, 53% reduction in gastroenteritis admissions and a total saving of 330 bed-days occupancy. There was an overall reduction in number of rotavirus-positive stool samples with 94% reduction in children aged under one year and a 65% reduction in those too old to have been vaccinated. In the first year after the introduction of universal vaccination against rotavirus we observed a profound reduction in gastroenteritis presentations and admissions with a substantial possible herd effect seen in older children. Extrapolating these findings to the UK population we estimate secondary healthcare savings in the first year of ca £7.5 (€10.5) million. Ongoing surveillance will be required to determine the long-term impact of the RV immunisation programme.

Prevalence of adenovirus and rotavirus infection in immunocompromised patients with acute gastroenteritis in Portugal

AIM: To characterize the prevalence of rotavirus (RV) and adenovirus (AdV) infections in immunocompromised patients with acute gastroenteritis.

METHODS: The presence of RV and AdV (serotypes 40 and 41) was evaluated in 509 stool samples obtained between January 2009 and December 2010 from 200 immunocompromised patients (83 females and 117 males; median age 21 years old, range 0-72. The diagnosis of infection was performed as a routine procedure and the presence of RV and AdV (serotypes 40 and 41) was determined by immunochromatography using the RIDA^® Quick Rota-Adeno-Kombi kit (r-Biopharm, Darmstadt, Germany). The data analysis and description of seasonal frequencies were performed using computer software IBM^® SPSS^® (Statistical Package for Social Sciences) Statistics version 20.0 for Mac. The frequencies of infection were compared into different age and gender groups by χ² test.

RESULTS: The study revealed 12.4% AdV positive samples and 0.8% RV positive samples, which correspond to a prevalence of 6.5% and 1.5%, respectively. AdV was more frequent between October 2009 and April 2010, while RV was identified in April 2010 and July 2010. The stool analysis revealed that from the 509 samples, 63 (12.4%) were positive for AdV and 4 (0.8%) positive for RV, which by resuming the information of each patient, lead to an overall prevalence of AdV and RV of 6.5% (13/200 patients) and 1.5% (3/200 patients), respectively. The stratification of the analysis regarding age groups showed a tendency to an increased prevalence of infection in paediatric patients between 0-10 years old. Considering the seasonal distribution of these infections, our study revealed that AdV infection was more frequent between October 2009 and April 2010, while RV infection was characterized by two distinct peaks (April 2010 and July 2010).

CONCLUSION: The overall prevalence of AdV and RV infection in immunocompromised patients with acute gastroenteritis was 8% and AdV was the most prevalent agent.

Case control study of rotavirus vaccine effectiveness in Portugal during 6 years of private market use

BACKGROUND

Although recommended by the vaccine committee of the Portuguese Paediatric Society, rotavirus vaccines have not been included in the routine immunization schedule. They have been available privately since 2006 with estimated coverage reaching approximately 30%. However, unlike other European countries using the vaccine, sentinel surveillance has detected fluctuations but no clear trends in the rate of gastrointestinal disease presentations. In this study, we set out to establish the real world effectiveness of rotavirus immunization in this low vaccine coverage setting.

METHODS

We carried out a test-negative case control study on a population of children attending a regional pediatric hospital, between 2006 and 2012, with symptoms of acute gastroenteritis and producing a stool sample for routine rotavirus testing. We calculated exposure odds ratio (ratio of odds of antecedent vaccination among cases compared with controls) to derive vaccine effectiveness ([1 - adjusted odds ratio]/100) against both hospital attendance and admission.

RESULTS

Vaccine effectiveness against attendance with rotavirus acute gastroenteritis was 83.7% (95% confidence interval: 73.9-89.8) and against hospital admission was 96.1% (95% confidence interval: 83.8-99.1). No significant difference between the 2 available vaccines was detected.

CONCLUSION

Both rotavirus vaccines offer a high degree of individual protection in this population.

Comparing cost-effectiveness results for a vaccine across different countries worldwide: what can we learn?

INTRODUCTION

Cost-effectiveness analysis (CEA) using country-specific thresholds tied to gross domestic product (GDP) might not be appropriate in countries with low healthcare investment and a high disease burden as a consequence.

METHODS

Using data from previously published CEA of rotavirus vaccination across nine countries worldwide, we calculated the cost neutral price (Pn) for the new intervention that reflects the price resulting in no net increase in health care costs compared with the current situation, and the maximum price (Pm) obtained with an incremental cost-effectiveness ratio (ICER) at the threshold value of 1×GDP/capita.

RESULTS

In countries with low GDP/capita, the paradoxical finding for rotavirus vaccination is that the Pm is much higher than in countries with a high GDP/capita. On the other hand, the Pn for the low GDP/capita countries is much lower than for high GDP/capita countries because of the low investment in health care.

CONCLUSION

In countries with low healthcare investment and a high disease burden, the difference between the Pn and Pm for rotavirus vaccine which is the price range within which the ICER is below the World Health Organization (WHO) threshold value, is large. One reason could be that the WHO threshold value may not properly account for the local opportunity cost of health care expenditures. Therefore, either alternative threshold values should be selected or alternative economic assessment tools should be considered, such as budget optimisation or return on investment, if we want to communicate about real economic value of new vaccines in those countries.