Rotavirus vaccine RIX4414 (Rotarix): a review of its use in the prevention of rotavirus gastroenteritis

The clinical development process for a novel preventive vaccine: An overview

Each novel vaccine candidate needs to be evaluated for safety, immunogenicity, and protective efficacy in humans before it is licensed for use. After initial safety evaluation in healthy adults, each vaccine candidate follows a unique development path. This article on clinical development gives an overview on the development path based on the expectations of various guidelines issued by the World Health Organization (WHO), the European Medicines Agency (EMA), and the United States Food and Drug Administration (USFDA). The manuscript describes the objectives, study populations, study designs, study site, and outcome(s) of each phase (Phase I-III) of a clinical trial. Examples from the clinical development of a malaria vaccine candidate, a rotavirus vaccine, and two vaccines approved for human papillomavirus (HPV) have also been discussed. The article also tabulates relevant guidelines, which can be referred to while drafting the development path of a novel vaccine candidate.

Immunogenicity and efficacy in mice of an adenovirus-based bicistronic rotavirus vaccine expressing NSP4 and VP7

NSP4 and VP7 are important functional proteins of rotavirus. Proper combination of viral gene expression is favorable to improving the protection effect of subunit vaccine. In the present study, We evaluated the immunogenicity and efficacy of the bicistronic recombinant adenovirus (rAd-NSP4-VP7) and two single-gene expressing adenoviruses (rAd-NSP4, rAd-VP7). The three adenovirus vaccines were used to immunize mice by intramuscular or intranasal administration. The data showed significant increases in serum antibodies, T lymphocyte subpopulations proliferation, and cytokine secretions of splenocyte in all immunized groups. However, the serum IgA and neutralizing antibody levels of the rAd-NSP4-VP7 or rAd-VP7 groups were significantly higher than those of the rAd-NSP4, while the splenocyte numbers of IFN-γ secretion in the rAd-NSP4-VP7 or rAd-NSP4 groups was greater than that of the rAd-VP7. Furthermore, the efficacy evaluation in a suckling mice model indicated that only rAd-NSP4-VP7 conferred significant protection against rotavirus shedding challenge. These results suggest that the co-expression of NSP4 and VP7 in an adenovirus vector induce both humoral and cell-mediated immune responses efficiently, and provide potential efficacy for protection against rotavirus disease. It is possible to represent an efficacious subunits vaccine strategy for control of rotavirus infection and transmission.

Tandem truncated rotavirus VP8* subunit protein with T cell epitope as non-replicating parenteral vaccine is highly immunogenic

The two currently available live oral rotavirus vaccines, Rotarix(®) and RotaTeq(®), are highly efficacious in the developed countries. However, the efficacy of such vaccines in resource deprived countries in Africa and Southeast Asia is low. We reported previously that a bacterially-expressed rotavirus P2-P[8] ΔVP8* subunit vaccine candidate administered intramuscularly elicited high-titers of neutralizing antibodies in guinea pigs and mice and significantly shortened the duration of diarrhea in neonatal gnotobiotic pigs upon oral challenge with virulent human rotavirus Wa strain. To further improve its vaccine potential and provide wider coverage against rotavirus strains of global and regional epidemiologic importance, we constructed 2 tandem recombinant VP8* proteins, P2-P[8] ΔVP8*-P[8] ΔVP8* and P2-P[8] ΔVP8*-P[6] ΔVP8* based on Escherichia coli expression system. The two resulting recombinant tandem proteins were highly soluble and P2-P[8] ΔVP8*-P[8] ΔVP8* was generated with high yield. Moreover, guinea pigs immunized intramuscularly by 3 doses of the P2-P[8] ΔVP8*-P[8] ΔVP8* or P2-P[8] ΔVP8*-P[6] ΔVP8* vaccine with aluminum phosphate adjuvant developed high titers of homotypic and heterotypic neutralizing antibodies against human rotaviruses bearing G1-G4, G8, G9 and G12 with P[8], P[4] or P[6] combination. The results suggest that these 2 subunit vaccines in monovalent or bivalent formulation can provide antigenic coverage to almost all the rotavirus G (VP7) types and major P (VP4) types of global as well as regional epidemiologic importance.

Inclusion of a universal tetanus toxoid CD4(+) T cell epitope P2 significantly enhanced the immunogenicity of recombinant rotavirus ΔVP8* subunit parenteral vaccines

Currently available live oral rotavirus vaccines, Rotarix(®) and RotaTeq(®), are highly efficacious in developed countries. However, the immunogenicity and efficacy of such vaccines in some developing countries are low. We reported previously that bacterially-expressed rotavirus ΔVP8* subunit vaccine candidates with P[8], P[4] or P[6] specificity elicited high-titer virus neutralizing antibodies in animals immunized intramuscularly. Of note was the finding that antibodies induced with the P[8]ΔVP8* vaccine neutralized both homotypic P[8] and heterotypic P[4] rotavirus strains to high titer. To further improve its vaccine potential, a tetanus toxoid universal CD4(+) T cell epitope P2 was introduced into P[8] or P[6]ΔVP8* construct. The resulting recombinant fusion proteins expressed in Escherichia coli were of high solubility and were produced with high yield. Two doses (10 or 20 μg/dose) of the P2-P[8]ΔVP8* vaccine or P2-P[6]ΔVP8* vaccine with aluminum phosphate adjuvant elicited significantly higher geometric mean homologous neutralizing antibody titers than the vaccines without P2 in intramuscularly immunized guinea pigs. Interestingly, high levels of neutralizing antibody responses induced in guinea pigs with 3 doses of the P2-P[8]ΔVP8* vaccine persisted for at least 6 months. Furthermore, in the gnotobiotic piglet challenge study, three intramuscular doses (50 μg/dose) of the P2-P[8]ΔVP8* vaccine with aluminum phosphate adjuvant significantly delayed the onset of diarrhea and significantly reduced the duration of diarrhea and the cumulative diarrhea score after oral challenge with virulent human rotavirus Wa (G1P[8]) strain. The P2-P[8]ΔVP8* vaccine induced serum virus neutralizing antibody and VP4-specific IgG antibody production prechallenge, and primed the pigs for higher antibody and intestinal and systemic virus-specific IFN-γ producing CD4(+) T cell responses postchallenge. These two subunit vaccines could be used at a minimum singly or preferably in bivalent formulation to provide antigenic coverage of most of the G types of global importance.

Characterization of RotaTeq® vaccine-derived rotaviruses in South Korean infants with rotavirus gastroenteritis

Genotyping of human rotaviruses was performed in 191 rotavirus-positive fecal samples collected from infants with acute gastroenteritis, 3 years after the introduction of two rotavirus vaccines in South Korea. Among these samples, the most prevalent rotavirus genotype was G3P[8] (30.9%), followed by G1P[8] (27.7%), G4P[6] (15.2%), and G9P[8] (5.8%). Sequence analysis identified RotaTeq® vaccine-derived strains in 12 samples (6.3%), comprising 11 G1P[8] human-bovine double reassortant rotaviruses and 1 G1P[5] human-bovine single reassortant rotavirus. It is of note that cross-reactivity between the current G4-specific typing primer and RotaTeq®-specific G1 genotypes was found. A trace of the clinical and environmental routes of the rotavirus vaccine strains revealed unexpected complexity, and the diagnostic protocol for rotaviruses may require modification by using either another typing primer set or nucleotide sequence analysis.

Pharmacoeconomic spotlight on rotavirus vaccine RIX4414 (Rotarix™) in developed countries

The most common cause of severe diarrhea in infants and young children is rotavirus gastroenteritis (RVGE), which is associated with significant morbidity, healthcare resource use, and direct and indirect costs in industrialized nations. The monovalent rotavirus vaccine RIX4414 (Rotarix™) is administered as a two-dose oral series in infants and has demonstrated protective efficacy against RVGE in clinical trials conducted in developed countries. In addition, various naturalistic studies have demonstrated ‘real-world’ effectiveness after the introduction of widespread rotavirus vaccination programs in the community setting.

Numerous cost-effectiveness analyses have been conducted in developed countries in which a universal rotavirus vaccination program using RIX4414 was compared with no universal rotavirus vaccination program. There was a high degree of variability in base-case results across studies even when the studies were conducted in the same country, often reflecting differences in the selection of data sources or assumptions used to populate the models. In addition, results were sensitive to plausible changes in a number of key input parameters. As such, it is not possible to definitively state whether a universal rotavirus vaccination program with RIX4414 is cost effective in developed countries, although results of some analyses in some countries suggest this is the case. In addition, international guidelines advocate universal vaccination of infants and children against rotavirus. It is also difficult to draw conclusions regarding the cost effectiveness of rotavirus vaccine RIX4414 relative to that of the pentavalent rotavirus vaccine, which is administered as a three-dose oral series. Although indirect comparisons in cost-effectiveness analyses indicate that RIX4414 provided more favorable incremental cost-effectiveness ratios when each vaccine was compared with no universal rotavirus vaccination program, results were generally sensitive to vaccine costs. Actual tender prices of a full vaccination course for each vaccine were not known at the time of the analyses and therefore had to be estimated.

[Incidence of rotavirus gastroenteritis among children under 5 years consulting a paediatrician or a general practitioner in France]

BACKGROUND

Rotavirus (RV) is the main infectious agent of severe acute gastroenteritis (AGE) in infants and children under 5 years. Given the recent availability of new vaccines, it is important to accurately assess the incidence of rotavirus gastroenteritis (GERV) and their medical and epidemiological consequences.

METHODS

This work is the French part of study program called SPRIK, a multicenter, prospective, observational study conducted from October 2005 to May 2007 to estimate the annual incidence of GERV within children under 5 years visiting a general practitioner or pediatrician. It presents data collected by 41 general practitioners and 36 paediatricians located throughout the French metropolitan territory. A stool sample was taken for every child. Rotavirus presence was sought by the physician using a rapid immunochromatographic test. French results are presented in this article.

RESULTS

A total of 1648 GEA episodes corresponding to 1463 eligible patients were included in the study mainly from December to May (peak in February-March). The incidence rate of GERV leading to consultations in general practice was 1357 cases per 100,000 patient-years (PY) (1.36%), with a 95% confidence interval of [1345-1368]. The peak incidence occurs before 2 years. GERV accounted for 21% of all GEA cases seen by paediatricians and general practitioners. Patients with GERV were younger (14.1 ± 10.8 versus 18.4 ± 13.9 months for other GEA, P<0.0001) and had more severe clinical symptoms: presence of fever (32.6% versus 20.0%, P<0.0001), behavioural symptoms (45.6% versus 20.8%, P<0.0001) and dehydration (48.7% versus 21.2%, P<0.0001). GERV episodes were considered severe in 79.7% of cases, using the Vesikari scale. More than 86% patients received oral rehydration during the episode and 13 patients (5.8%) were hospitalized. Nearly 80% GERV episodes were considered severe using the Vesikari scale. Main genotypes were G1P[8] rotavirus (44%) and G9P[8] rotavirus (35%) types.

CONCLUSION

The incidence rate reported in this study is close to results of previous studies done in Europe. The frequency and severity relative to GERV support vaccination in very young children to reduce the burden associated with this pathology.

Pharmacoeconomic spotlight on rotavirus vaccine RIX4414 (Rotarix™) in the prevention of rotavirus gastroenteritis in developing countries

This article provides an overview of the clinical profile of rotavirus vaccine RIX4414 (Rotarix™) in the prevention of rotavirus gastroenteritis (RVGE) in developing countries, followed by a review of pharmacoeconomic analyses with the vaccine in low- and middle-income countries. RVGE is associated with significant morbidity and mortality among children <5 years of age in developing countries. The protective efficacy of a two-dose oral series of rotavirus vaccine RIX4414 has been demonstrated in several well designed clinical trials conducted in developing countries, and the 'real-world' effectiveness of the vaccine has also been shown in naturalistic and case-control trials after the introduction of universal vaccination programs with RIX4414 in Latin American countries. The WHO recommends universal rotavirus vaccination programs for all countries. Numerous modelled cost-effectiveness analyses have been conducted with rotavirus vaccine RIX4414 across a wide range of low- and middle-income countries. Although data sources and assumptions varied across studies, results of the analyses consistently showed that the introduction of the vaccine as part of a national vaccination program would be very cost effective compared with no rotavirus vaccination program, according to widely used cost-effectiveness thresholds for developing countries. Vaccine price was not known at the time the analyses were conducted and had to be estimated. In sensitivity analyses, rotavirus vaccine RIX4414 generally remained cost effective at the highest of a range of possible vaccine prices considered. Despite these favorable results, decisions regarding the implementation of universal vaccination programs with RIX4414 may also be contingent on budgetary and other factors, underscoring the importance of subsidized vaccination programs for poor countries through the GAVI Alliance (formerly the Global Alliance for Vaccines and Immunization).

Construction and characterization of human rotavirus recombinant VP8* subunit parenteral vaccine candidates

Two currently licensed live oral rotavirus vaccines (Rotarix® and RotaTeq®) are highly efficacious against severe rotavirus diarrhea. However, the efficacy of such vaccines in selected low-income African and Asian countries is much lower than that in middle or high-income countries. Additionally, these two vaccines have recently been associated with rare case of intussusception in vaccinated infants. We developed a novel recombinant subunit parenteral rotavirus vaccine which may be more effective in low-income countries and also avert the potential problem of intussusception. Truncated recombinant VP8* (ΔVP8*) protein of human rotavirus strain Wa P[8], DS-1 P[4] or 1076 P[6] expressed in Escherichia coli was highly soluble and was generated in high yield. Guinea pigs hyperimmunized intramuscularly with each of the ΔVP8* proteins (i.e., P[8], P[4] or P[6]) developed high levels of homotypic as well as variable levels of heterotypic neutralizing antibodies. Moreover, the selected ΔVP8* proteins when administered to mice at a clinically relevant dosage, route and schedule, elicited high levels of serum anti-VP8* IgG and/or neutralizing antibodies. Our data indicated that the ΔVP8* proteins may be a plausible additional candidate as new parenteral rotavirus vaccines.

Immunogenicity and safety of 10-valent pneumococcal non-typeable Haemophilus influenzae protein D-conjugate vaccine (PHiD-CV) co-administered with routine childhood vaccines in Taiwan

BACKGROUND/PURPOSE

The immunogenicity and safety of the 10-valent pneumococcal nontypeable Haemophilus influenzae (H. Influenzae) protein D conjugate vaccine (PHiD-CV), co-administered with routine childhood vaccines, were assessed in Taiwanese infants.

METHODS

In this open study, 230 healthy infants were primed with three doses of PHiD-CV (Synflorix) and diphtheria, tetanus, acellular pertussis, hepatitis B (HBV), inactivated poliomyelitis and Haemophilus influenzae type b (Hib) conjugate vaccine (DTPa-HBV-IPV/Hib vaccine) at 1.5, 3 and 6 months of age and two doses of oral human rotavirus vaccine at 1.5 and 3 months. Pneumococcal immune responses were assessed 1 month post-dose three, by 22F-inhibition ELISA and opsonophagocytic activity (OPA) assay. Local and general solicited/unsolicited symptoms and serious adverse events (SAEs) were recorded.

RESULTS

At least 95.4% of participants had an antibody concentration ≥ 0.2 μg/mL against each vaccine serotype. At least 96.1% of participants had an OPA titer ≥ 8 against each vaccine serotype except 6B (87.3%). All infants, but one, were seropositive for antibodies against nontypeable H. influenzae protein D. Immune responses to the co-administered vaccines were good and in line with previous reports. PHiD-CV was well tolerated, with low (≤ 6.3%) incidences of grade 3 solicited local symptoms. The frequencies of general symptoms were in line with other pneumococcal conjugate vaccine studies. There were no systematic increases in incidences of solicited general or local symptoms with successive doses. There were no reports of grade 3 fever (rectal temperature > 40 °C) or SAEs considered to be causally related to vaccination.

CONCLUSION

PHiD-CV co-administered with routine childhood vaccines within the first 6 months of life, was highly immunogenic, and well tolerated in Taiwanese infants.

Rotavirus vaccine RIX4414 (Rotarix™): a pharmacoeconomic review of its use in the prevention of rotavirus gastroenteritis in developing countries

This article provides an overview of the clinical profile of rotavirus vaccine RIX4414 (Rotarix™) in the prevention of rotavirus gastroenteritis (RVGE) in developing countries, followed by a comprehensive review of pharmacoeconomic analyses with the vaccine in low- and middle-income countries. RVGE is associated with significant morbidity and mortality among children <5 years of age in developing countries. The protective efficacy of a two-dose oral series of rotavirus vaccine RIX4414 has been demonstrated in several well designed clinical trials conducted in developing countries, and the 'real-world' effectiveness of the vaccine has also been shown in naturalistic and case-control trials after the introduction of universal vaccination programmes with RIX4414 in Latin American countries. The WHO recommends universal rotavirus vaccination programmes for all countries. Numerous modelled cost-effectiveness analyses have been conducted with rotavirus vaccine RIX4414 across a wide range of low- and middle-income countries. Although data sources and assumptions varied across studies, results of the analyses consistently showed that the introduction of the vaccine as part of a national vaccination programme would be very (or highly) cost effective compared with no rotavirus vaccination programme, according to widely used cost-effectiveness thresholds for developing countries. Vaccine price was not known at the time the analyses were conducted and had to be estimated. In sensitivity analyses, rotavirus vaccine RIX4414 generally remained cost effective at the highest of a range of possible vaccine prices considered. Despite these favourable results, decisions regarding the implementation of universal vaccination programmes with RIX4414 may also be contingent on budgetary and other factors, underscoring the importance of subsidized vaccination programmes for poor countries through the GAVI Alliance (formerly the Global Alliance for Vaccines and Immunization).

Rotavirus vaccine RIX4414 (Rotarix™): a pharmacoeconomic review of its use in the prevention of rotavirus gastroenteritis in developed countries

The most common cause of severe diarrhoea in infants and young children is rotavirus gastroenteritis (RVGE), which is associated with significant morbidity, healthcare resource use and direct and indirect costs in industrialized nations. The monovalent rotavirus vaccine RIX4414 (Rotarix™) is administered as a two-dose oral series in infants and has demonstrated protective efficacy against RVGE in clinical trials conducted in developed countries. In addition, various naturalistic studies have demonstrated 'real-world' effectiveness after the introduction of widespread rotavirus vaccination programmes in the community setting. Numerous cost-effectiveness analyses have been conducted in developed countries in which a universal rotavirus vaccination programme using RIX4414 was compared with no universal rotavirus vaccination programme. There was a high degree of variability in base-case results across studies even when conducted in the same country, often reflecting differences in the selection of data sources or assumptions used to populate the models. In addition, results were sensitive to plausible changes in a number of key input parameters. As such, it is not possible to definitively state whether a universal rotavirus vaccination programme with RIX4414 is cost effective in developed countries, although results of some analyses in some countries suggest this is the case. In addition, international guidelines advocate universal vaccination of infants and children against rotavirus. It is also difficult to draw conclusions regarding the cost effectiveness of rotavirus vaccine RIX4414 relative to that of the pentavalent rotavirus vaccine, which is administered as a three-dose oral series. Although indirect comparisons in cost-effectiveness analyses indicate that RIX4414 provided more favourable incremental cost-effectiveness ratios when each vaccine was compared with no universal rotavirus vaccination programme, results were generally sensitive to vaccine costs. Actual tender prices of a full vaccination course for each vaccine were not known at the time of the analyses and therefore had to be estimated.

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.

Update on Rotarix: an oral human rotavirus vaccine

Worldwide, rotaviruses are the single most important agents of severe gastroenteritis in infants and young children. Globally, it is estimated that every year rotavirus gastroenteritis causes more than 125 million episodes of diarrhea and nearly 527,000 deaths, mainly in developing countries. The development of new effective and safe rotavirus vaccines was recognized as the most effective intervention strategy that could yield a significant impact on the burden of rotavirus disease. Rotarix is an oral live-attenuated human rotavirus vaccine containing a single G1P[8] strain. The first oral dose may be administered as early as 6 weeks of age, with a minimum interval of 4 weeks prior to second dose; the vaccination course should be completed by the age of 24 weeks according to the manufacturer. In the USA, the upper age limit for the second dose has recently been recommended at 32 weeks of age by the Advisory Committee on Immunization Practices. The development program for Rotarix including Phase I, II and III multicenter studies involving over 100,000 infants has been established in Latin America, Europe, Asia and Africa. The vaccine proved to be well tolerated, immunogenic, efficacious, safe and not associated with intussusception. It provided 85-96% protection against severe rotavirus gastroenteritis caused by G1 and non-G1 serotypes in Latin American and European clinical trials; and of public health importance, Rotarix reduced hospitalizations of all-cause gastroenteritis by 40 and 75%, respectively. Efficacy against G2P[4] strains ranged from 41% in Latin America to 81% in Europe. In the former, Rotarix afforded sustained high protection (80.5%; 95% CI: 71.3-87.1) against severe rotavirus gastroenteritis during the first 2 years of life in a region with a changing pattern of wild-type rotavirus circulation. In a recently completed vaccine trial in South Africa and Malawi, Rotarix showed an overall efficacy of 61.2% (95% CI: 44.0-73.2) by 1 year of age. Although these rates are lower than those from developed and middle-income countries, they look promising given the lack of other effective interventions. With the expanding introduction of rotavirus vaccines into national immunization programs, postmarketing surveillance should be conducted to measure the impact of rotavirus vaccination, as well as continued monitoring of circulating rotavirus strains.

Sibling transmission of vaccine-derived rotavirus (RotaTeq) associated with rotavirus gastroenteritis

Although rotavirus vaccines are known to be shed in stools, transmission of vaccine-derived virus to unvaccinated contacts resulting in symptomatic rotavirus gastroenteritis has not been reported to our knowledge. We document here the occurrence of vaccine-derived rotavirus (RotaTeq [Merck and Co, Whitehouse Station, NJ]) transmission from a vaccinated infant to an older, unvaccinated sibling, resulting in symptomatic rotavirus gastroenteritis that required emergency department care. Results of our investigation suggest that reassortment between vaccine component strains of genotypes P7[5]G1 and P1A[8]G6 occurred during replication either in the vaccinated infant or in the older sibling, raising the possibility that this reassortment may have increased the virulence of the vaccine-derived virus. Both children remain healthy 11 months after this event and are without underlying medical conditions.