Live Attenuated Human Rotavirus Vaccine, Rotarix™

Fourteen years' clinical experience and the first million babies protected with human live-attenuated vaccine against rotavirus disease in Italy

Rotavirus (RV) causes up to half of hospital and community acute gastroenteritis (AGE) cases in young children in Italy. Two RV vaccines, available since 2006, are human RV (HRV) and human bovine RV (HBRV). This report looks back at the implementation of RV vaccination with HRV in Italy, and at HRV current and future perspectives. Initial regional policies led to national implementation by 2018, after scientific societies' disease awareness efforts. Following vaccination, RV hospitalizations declined significantly, and cost savings were observed. The two-dose HRV vaccine is easily administered during compulsory vaccine visits, helping increase coverage. Intussusception, a serious event in children <1 year, was reported in Italy with a rate of 33-40 per 100,000 infants. RV vaccination presents a low increased risk of intussusception after the first dose, estimated at 0.6 cases per 100,000 doses in Italy in 2019. Parents should be aware of the intussusception risk and symptoms to ensure prompt treatment. It is widely recognized that the vaccination benefits (large numbers of RV hospitalizations prevented) outweigh the risk. HRV introduction in Italy was supported by epidemiologic burden studies, healthcare provider opinions, and congress debates, which significantly contributed to implementation of RV universal routine infant vaccination in Italy.

Unexpected Role of Rotavirus G3P[8] Infection in Causing Severe Diarrhea in a Major Tertiary Referral Hospital in the Prevaccine Era

Background: Rotavirus A species is associated with severe gastroenteritis in children. Rotavirus G1P[8] was the most prevalent genotype found in Kuwait in a study conducted between 2005 and 2006. The RotaTeq vaccine was included in the Kuwait national immunization program at the end of 2017. Objectives: Since there is no available data on the rotavirus genotypes circulating before the introduction of the vaccine, we conducted a study to investigate the role of rotaviruses in causing severe diarrhea in children hospitalized in a major tertiary referral hospital in Kuwait during the year 2016. Methods: Viral RNA was isolated from the stool samples of 101 children under five years of age, hospitalized for acute gastroenteritis. Rotavirus VP4 and VP7 dsRNA were detected by RT-PCR, and their partial sequences were analyzed by phylogenic analysis. Results: Rotavirus dsRNA was detected in 24.7% of children with median age of 1 year. The genotype G3P[8] accounted for 47% of cases, followed by G1P[8] (26%), G9P[8] (10.5%), G4P[8] (10.5%), and G9P[4] (5%). Only VP7 nucleotide sequences of rotavirus G3 or G4 type clustered in the same lineage as RotaTeq vaccine, while most VP4 nucleotide sequences of rotavirus P[8] type clustered in a different lineage compared to Rotarix and RotaTeq vaccines. Conclusions: Our findings highlight the role of rotavirus G3P[8] in causing severe diarrhea and invites future investigations to know whether the recent introduction of RotaTeq vaccine in Kuwait selects certain genotypes and subgenomic lineages.

Fifteen years of experience with the oral live-attenuated human rotavirus vaccine: reflections on lessons learned

INTRODUCTION

Rotavirus (RV) disease remains a prominent cause of disease burden in children <5 years of age worldwide. However, implementation of RV vaccination has led to significant reductions in RV mortality, compared to the pre-vaccination era. This review presents 15 years of real-world experience with the oral live-attenuated human RV vaccine (HRV; Rotarix). HRV is currently introduced in ≥80 national immunization programs (NIPs), as 2 doses starting from 6 weeks of age.

AREAS COVERED

The clinical development of HRV and post-marketing experience indicating the impact of HRV vaccination on RV disease was reviewed.

EXPERT OPINION

In clinical trials, HRV displayed an acceptable safety profile and efficacy against RV-gastroenteritis, providing broad protection against heterotypic RV strains by reducing the consequences of severe RV disease in infants. Real-world evidence shows substantial, rapid reduction in the number of RV infections and associated hospitalizations following introduction of HRV in NIPs, regardless of economic setting. Indirect effects against RV disease are also observed, such as herd protection, decrease in nosocomial infections incidence, and a reduction of disease-related societal/healthcare costs. However, not all countries have implemented RV vaccination. Coverage remains suboptimal and should be improved to maximize the benefits of RV vaccination.

Cell culture-based viral vaccines: current status and future prospects

Cell culture-based viral vaccines are used globally to immunize humans against infections. The cell culture is continuous process of developing substrates for the safe production of viral vaccines. However, increased global demand and strict safety rules for novel vaccines to control and eradicate viral diseases have forced researchers and manufacturers toward cell culture-based vaccines. The choice of cell substrate is a critical step that cannot be generalized for every vaccine formulation, therefore, manufacturers intend to optimize the required processes for particular applications. The recently established cell lines, innovative bioreactor concepts and cultivation schemes are necessary to increase the potential of vaccine production. In this review, we have focused on current cell culture-based viral vaccines and their future prospects.

Inhibitory Effect of a Hot-Water Extract of Leaves of Japanese Big-Leaf Magnolia (Magnolia obovata) on Rotavirus-Induced Diarrhea in Mouse Pups

The leaf of Japanese big-leaf magnolia (Magnolia obovata Thunb.) has long been used as a natural packaging material for traditional foods in Japan. However, many of the physiological functions of the leaves against oral infection and resultant illness remain unclear. The aim of the present study was to investigate the effects of a hot-water extract of the leaves of Magnolia obovata on diarrhea induced by rotavirus (RV), a major cause of acute diarrhea. RV strain SA11 was mixed with the M. obovata leaf extract and inoculated orally to neonatal BALB/c mouse pups. Simultaneous inoculation of SA11 with the extract significantly decreased the incidence of diarrhea. In addition, the extract significantly inhibited cytopathic effects and mRNA expression of viral proteins in SA11-infected MA104 cells. Two flavonoid glycosides, quercitrin and rutin, were strongly suggested to be major anti-RV agents in the extract by serial solvent extraction and reversed-phase HPLC-ESI-MS analysis. Our results suggest that the hot-water extract of M. obovata leaves can be used as a medicine or food additive to prevent and ameliorate RV-induced diarrhea in individuals that may have difficulty in benefitting from the RV vaccines.

Immunogenicity of novel mumps vaccine candidates generated by genetic modification

Mumps is a highly contagious human disease, characterized by lateral or bilateral nonsuppurative swelling of the parotid glands and neurological complications that can result in aseptic meningitis or encephalitis. A mumps vaccination program implemented since the 1960s reduced mumps incidence by more than 99% and kept the mumps case numbers as low as hundreds of cases per year in the United States before 2006. However, a large mumps outbreak occurred in vaccinated populations in 2006 and again in 2009 in the United States, raising concerns about the efficacy of the vaccination program. Previously, we have shown that clinical isolate-based recombinant mumps viruses lacking expression of either the V protein (rMuVΔV) or the SH protein (rMuVΔSH) are attenuated in a neurovirulence test using newborn rat brains (P. Xu et al., Virology 417:126-136, 2011, http://dx.doi.org/10.1016/j.virol.2011.05.003; P. Xu et al., J. Virol. 86:1768-1776, 2012, http://dx.doi.org/10.1128/JVI.06019-11) and may be good candidates for vaccine development. In this study, we examined immunity induced by rMuVΔSH and rMuVΔV in mice. Furthermore, we generated recombinant mumps viruses lacking expression of both the V protein and the SH protein (rMuVΔSHΔV). Analysis of rMuVΔSHΔV indicated that it was stable in tissue culture cell lines. Importantly, rMuVΔSHΔV was immunogenic in mice, indicating that it is a promising candidate for mumps vaccine development.

Introduction of rotavirus vaccines in developing countries: remaining challenges

Rotavirus is the principal agent of severe, dehydrating gastro-enteritis in infants and young children worldwide. The main public health tool that can prevent hospitalisation and death from rotavirus is vaccination. One of two current rotavirus vaccines is now licensed in more than 80 countries and is incorporated into childhood immunisation schedules across several countries in the Americas and Europe. However, since the majority of childhood deaths from rotavirus occur in the developing countries of Africa and Asia, widespread use of vaccine in these two continents will be necessary before a major impact on global diarrhoea mortality is seen. Challenges in these latter settings which primarily relate to vaccine efficacy, safety and financing will be addressed within the next 3-5 years, and thus perhaps finally allow introduction of rotavirus vaccine into the populations in greatest need.

Prevention of rotavirus gastroenteritis in infants and children: rotavirus vaccine safety, efficacy, and potential impact of vaccines

Rotavirus infection is the most common cause of severe gastroenteritis globally, with greater than 86% of deaths occurring in low-income and middle-income countries. There are two rotavirus vaccines currently licensed in the United States and prequalified by the World Health Organization. RV1 is a monovalent attenuated human rotavirus strain, given orally in two doses. RV5 is a pentavalent human-bovine reassortant rotavirus vaccine, given orally in three doses. A third rotavirus vaccine, LLV, is a lamb rotavirus strain given orally as a single dose, which is currently available only in China. RV1 and RV5 have been shown to be highly efficacious in developed countries, and initial results from trials in Africa and Asia are promising as well. At least three other vaccines are in development, which are being developed by manufacturers of developing countries. Further studies are needed to clarify issues including administration of oral rotavirus vaccines with breastfeeding and other oral vaccines, and alterations in dosing schedule. Using new data on global diarrheal burden, rotavirus is estimated to cause 390,000 deaths in children younger than 5 years. Should rotavirus vaccines be introduced in the routine immunization programs of all countries, a potential of 170,000 deaths could be prevented annually. The largest impact on mortality would be seen in low-income and middle-income countries, despite poor immunization coverage and lower efficacy. Therefore, international efforts are needed to ensure that rotavirus vaccines reach the populations with highest burden of rotavirus disease.

The effect of rotavirus vaccine on diarrhoea mortality

Background Approximately 39% of the global diarrhoea deaths in children aged 5 years may be attributable to rotavirus infection. Two rotavirus vaccines were recently introduced to the market, with evidence of efficacy in the USA, Europe and Latin America. We sought to estimate the effectiveness of these vaccines against rotavirus morbidity and mortality.

Methods We conducted a systematic review of published efficacy and effectiveness trials of rotavirus vaccines. Study descriptors and outcome measures were abstracted into standardized tables and the quality of each study was graded. We performed meta-analyses for any outcome with two or more data points, and used child health epidemiology reference group (CHERG) Rules for Evidence Review to estimate the effect of the vaccine on rotavirus mortality.

Results We identified six papers for abstraction, reporting results from four studies. No studies reported diarrhoea or rotavirus deaths, but all studies showed reductions in hospitalizations due to rotavirus or diarrhoea of any aetiology, severe and any rotavirus infections and diarrhoea episodes of any aetiology in children who received rotavirus vaccine compared with placebo. Effectiveness against very severe rotavirus infection best approximated effectiveness against the fraction of diarrhoea deaths attributable to rotavirus, and was estimated to be 74% (95% confidence interval: 35–90%).

Conclusions Rotavirus vaccines are efficacious against rotavirus morbidity and mortality and have the potential to substantially reduce child mortality in low-income countries if implemented appropriately.

Vero cell platform in vaccine production: moving towards cell culture-based viral vaccines

The development of cell culture systems for virus propagation has led to major advances in virus vaccine development. Primary and diploid cell culture systems are now being replaced by the use of continuous cell lines (CCLs). These substrates are gaining increasing acceptance from regulatory authorities as improved screening technologies remove fears regarding their potential oncogenic properties. The Vero cell line is the most widely accepted CCL by regulatory authorities and has been used for over 30 years for the production of polio and rabies virus vaccines. The recent licensure of a Vero cell-derived live virus vaccine (ACAM2000, smallpox vaccine) has coincided with an explosion in the development of a range of new viral vaccines, ranging from live-attenuated pediatric vaccines against rotavirus infections to inactivated whole-virus vaccines against H5N1 pandemic influenza. These developments have illustrated the value of this cell culture platform in the rapid development of vaccines against a range of virus diseases.

Intussusception

Intussusception is the most common cause of intestinal obstruction in children between 3 months and 6 years. Intussusception occurs when a more proximal portion of bowel invaginates into more distal bowel. These patients often present with a wide range of non-specific symptoms, with less than one quarter presenting with the classic triad of vomiting, abdominal pain, and bloody stools. Thus, the diagnosis continues to rely on clinical suspicion. This review article discusses the clinical presentation of intussusception and the state-of-the art diagnostic and treatment options, as well as a review of the pertinent literature.

Predominance of rotavirus P[4]G2 in a vaccinated population, Brazil

We identified 21 rotaviruses in 129 patients with diarrhea in a Brazilian city with high rotavirus vaccine coverage. All rotaviruses were genotype P[4]G2 with 1 mixed infection with P[NT]G9. Although virus predominance could have occurred randomly, the vaccine may be less protective against P[4]G2. Prospective surveillance is urgently needed.

Rotavirus vaccines: entering a new stage of deployment

PURPOSE OF REVIEW

Rotavirus is the single most important cause of severe diarrhoea in infants and young children. This review provides updated information concerning three rotavirus vaccines that are being evaluated and introduced globally.

RECENT FINDINGS

Two large, phase III clinical trials, each involving more than 60,000 infants in both developing and developed countries, demonstrated that both RotaTeq (Merck & Co., Whitehouse Station, New Jersey, USA), the pentavalent human-bovine reassortant vaccine, and Rotarix (GlaxoSmithKine Biologicals, Rixensart, Belgium), the monovalent live-attenuated human rotavirus vaccine, are safe with respect to intussusception when the first dose is administered between 6 and 12 weeks of age, and that both vaccines are 90-95% efficacious in preventing severe rotavirus gastroenteritis including hospitalization. The bovine (UK)-human rotavirus reassortant tetravalent (BRV-TV) vaccine, developed at the National Institutes of Health (USA), was licensed for local production in several developing countries.

SUMMARY

Rotavirus vaccines are entering a new stage of deployment toward the goal of reducing morbidity and mortality attributed to rotavirus infection in developing countries, and hospitalizations and emergency visits caused by rotavirus in developed countries. High vaccine prices appear to offset cost savings, and may make policymakers even in wealthy countries hesitate to introduce a rotavirus vaccine into their childhood immunization programmes.

Group A rotavirus genotypes in Germany during 2005/2006

During the 2005/2006 winter season a total of 802 group A positive rotavirus specimens of patients from different regions throughout Germany were genotyped. Amplicons from a one-tube RT-PCR were typed by analysis of their (type-specific) size using type-specific primers, fluorescent consensus primers and a capillary sequencer for detection. While G1P[8] was predominant (45.8%), G9P[8] has emerged as the second most frequent genotype combination (37.7%). The distribution of genotypes was heterogeneous, regional frequencies regarding G1 and G9 were ranging from 15.0 to 89.3% and from 7.1 to 67.7%, respectively. Furthermore, a few human rotavirus G10P[6] and G10P[8] infections were observed.

Molecular epidemiology of rotavirus in Central and Southeastern Europe

A surveillance network was implemented by the Istituto Superiore di Sanità of Rome in collaboration with laboratories of virology in Czech Republic, Slovenia, Croatia, Albania, and Bulgaria. About 1,500 rotavirus-positive stool samples were collected from children with severe gastroenteritis admitted to hospitals or outpatient wards between 2004 and 2006. The G and P genotypes were determined by reverse transcription-nested PCR. Significant differences were found in the geographical distributions of rotavirus genotypes between countries participating in the study. The prevalence of "common" G/P combinations, G1P[8], G3P[8], G4P[8], and G2P[4], ranged between 50 and 85%. The G9 genotype, which is emerging worldwide, was identified in 2 to 35% of all samples depending on the country. Unusual combinations, such as G1 or G4 associated with P[4] or G2 with P[8], which may have arisen by reassortment between human strains, were found in samples from 3 to 20% of patients. The uncommon genotypes G8P[8] and G10P[6], which may have an animal origin, were also identified. Double infections with two rotavirus strains were observed in between 1.7 and 14% of cases studied. Our findings might implicate challenges for rotavirus vaccine implementation in a wide geographic area of the Balkans and Central-Eastern Europe and underscore the importance of extensive strain surveillance for success in vaccine development.