Effect of rotavirus vaccination on death from childhood diarrhea in Mexico

Co-dominance of G1 and emerging G3 rotaviruses in Hong Kong: a three-year surveillance in three major hospitals

BACKGROUND

The World Health Organization recommends rotavirus vaccines be included in all national immunization programs as part of a strategy to control diarrhoeal diseases. Sentinel surveillance is advised to monitor impact post-vaccine introduction and to document changes in genotype distribution.

OBJECTIVES

To determine the molecular epidemiology of circulating rotaviruses in Hong Kong prior to implementation of universal rotavirus vaccination.

STUDY DESIGN

From December 2004 through December 2007, 830 rotavirus-positive stool samples from subjects admitted for acute diarrhea to three major hospitals in Hong Kong were examined. The electropherotypes, and the G and P genotypes of these rotaviruses were determined. Phylogenetic analysis of the VP7 gene was performed.

RESULTS

G3P[8] was the dominant genotype (46.1%), followed by G1P[8] (36.5%) and G9P[8] (9.2%). A total of 35 electropherotypes were identified. The G3 and G1 strains had high sequence similarities among themselves and were clustered with strains from Asia particularly mainland China. The G9 strains were clustered with the globally spreading strains. G12 and G4 were not found. The prevalence of rotavirus infection peaked in winter season when temperature was low, atmospheric pressure was high, relative humidity was low and rainfall was negligible.

CONCLUSIONS

Genotype G3 and G1 were the dominant rotaviruses circulating in Hong Kong between 2004 and 2007. Strains were mainly related with those from mainland China. Ongoing surveillance of circulating genotypes should continue in anticipation of universal rotavirus vaccine introduction.

Impact of rotavirus vaccination on diarrhea-related hospitalizations among children < 5 years of age in Mexico

BACKGROUND

Single-strain rotavirus vaccine was added to the national immunization program in Mexico in May 2007. We assessed the impact of vaccination on the number of diarrhea-related hospitalizations in Mexican children in 2008 and 2009.

METHODS

We obtained data on all-cause diarrhea-related hospitalizations from January 2003 to June 2009 in Mexican children <5 years of age. We compared diarrhea-related hospitalizations during the 2008 and 2009 rotavirus seasons with the median number of diarrhea-related hospitalizations at baseline (2003-2006), before rotavirus vaccine introduction, at 306 Ministry of Health hospitals. We estimated vaccine coverage using administrative data.

RESULTS

A median number of 10,993 diarrhea-related hospitalizations (range: 9877-11958) occurred each prevaccine rotavirus season from 2003 to 2006 among children < 5 years of age. Diarrhea-related hospitalizations decreased by 11% (N = 9836) in 2008 and by 40% (N = 6597) in 2009. The greatest declines occurred in infants < 12 months of age during 2008 (25%) and 2009 (52%), with 1-dose rotavirus vaccination coverage of 74% and 89% during these years, respectively. A 43% decline was also noted among children 12 to 23 months of age during the 2009 season. No declines were noted during either 2008 or 2009 among unvaccinated children >24 months of age during the study period.

CONCLUSIONS

Marked declines in diarrhea-related hospitalizations among vaccine-eligible Mexican children < 24 months of age have occurred during the first 2 complete rotavirus seasons following rotavirus vaccination. Rotavirus-specific surveillance and epidemiologic studies are necessary for a better understanding of the changes in disease epidemiology and public health impact from rotavirus vaccination.

Distribution of rotavirus genotypes after introduction of rotavirus vaccines, Rotarix® and RotaTeq®, into the National Immunization Program of Australia

BACKGROUND

Rotavirus vaccines, RotaTeq and Rotarix, were introduced into the Australian National Immunization Program on July 1, 2007. The simultaneous introduction in different Australian states and territories provides a unique opportunity to compare the affect of each vaccine on the types of circulating rotavirus strains. This report describes the rotavirus genotypes responsible for the hospitalization of children during the first 2-year period after vaccine introduction.

METHODS

A total of 764 rotavirus-associated diarrheal cases were collected from children presenting to hospital in 10 Australian centers. Rotavirus genotype was determined using reverse transcription polymerase chain reaction assays.

RESULTS

G1P[8] was the dominant genotype nationally (52%), followed by G2P[4] (19.8%), G9P[8] (12.2%), and G3P[8] (11%). Differences in the prevalence rates of G2P[4] and G3P[8] were seen in the various states. G2P[4] strains were more prevalent in states using Rotarix, whereas G3P[8] strains were more prevalent in states using RotaTeq.

CONCLUSIONS

Differences in rotavirus genotypes were observed across Australia, which suggest that different immune pressures are exerted by the different vaccines, but do not necessarily imply lack of protection by either vaccine. These differences may simply be related to the variation that can occur because of natural annual fluctuation in rotavirus strain prevalence.

Immunogenicity and virus-like particle formation of rotavirus capsid proteins produced in transgenic plants

The human pathogen, group A rotavirus, is the most prevalent cause of acute infantile and pediatric gastroenteritis worldwide, especially in developing countries. There is an urgent demand for safer, more effective and cheaper vaccines against rotavirus infection. Plant-derived antigens may provide an exclusive way to produce economical subunit vaccines. Virus-like particles, constituting viral capsid proteins without viral nucleic acids, are considered a far safer candidate compared with live attenuated viral vaccines. In this study, the rotavirus capsid proteins VP2, VP6 and VP7 were co-expressed in transgenic tobacco plants, and their expression levels, formation of rotavirus-like particles (RV VLPs) and immunogenicity were extensively studied. Quantitative real-time RT-PCR and Western blot analysis revealed that the expression level of vp6 was the highest while vp7 was expressed at the lowest levels. The RV VLPs were purified from transgenic tobacco plants and analyzed by electron microscopy and Western blot. Results indicated that the plant-derived VP2, VP6 and VP7 proteins self-assembled into 2/6 or 2/6/7 RV VLPs with a diameter of 60-80 nm. When orally delivered into mice with cholera toxin as an adjuvant, the total soluble protein extracted from transgenic tobacco plants induced rotavirus-specific antibodies comparable with those of attenuated rotavirus vaccines, while VP 2/6/7 induced higher serum IgG and fecal IgA titers compared with VP 2/6.

Maternal antibodies to rotavirus: could they interfere with live rotavirus vaccines in developing countries?

INTRODUCTION

Past experience with live oral vaccines including licensed rotavirus vaccines demonstrates a trend towards reduced vaccine efficacy in developing countries compared with developed countries. The reasons behind this disparity are not well understood. Transplacental transfer of maternal antibodies and breast milk ingestion may attenuate vaccine responses in infants in developing countries where rotavirus infections are endemic, and maternal antibody levels are high. We examined the prevalence and level of rotavirus antibody in maternal and cord serum, colostrum and breast milk in a developing country setting.

METHODS

100 mother-infant pairs were prospectively recruited from December 2008 to February 2009 at Dr. Sardjito Hospital, Yogyakarta, Indonesia. Maternal and cord sera were collected during delivery. Colostrum and transitional breast milk were collected between day 0-3 and day 7-10 postpartum respectively. Rotavirus-specific IgA and IgG were estimated for all specimens and virus neutralization assays were conducted on a subset of milk specimens.

RESULTS

All maternal and cord serum samples were positive for rotavirus-specific IgG antibodies with a strong correlation between levels of rotavirus-specific IgG in mothers and levels transferred to infants in cord blood (r=0.86; p=0.001). 78% of colostrum and 67% of transitional breast milk specimens were positive for rotavirus-specific IgA. There was a median 4-fold decrease in rotavirus-specific IgA from colostrum to transitional breast milk. Neutralizing antibodies were present in 56% of colostrum specimens assayed (19/34) and in 41% of transitional milk specimens assayed (14/34).

CONCLUSIONS

Maternal serum and breast milk antibodies to rotavirus are highly prevalent in a developing country setting. Evaluation of the impact of maternal anti-rotavirus serum and breast milk antibody upon vaccine immunogenicity would help to inform rotavirus vaccination strategies, especially in developing settings.

Pentavalent rotavirus vaccine in developing countries: safety and health care resource utilization

OBJECTIVE

In the international, placebo-controlled, Rotavirus Efficacy and Safety Trial, the pentavalent rotavirus vaccine reduced the rate of rotavirus-attributable hospitalizations and emergency department visits by 95%. This study investigated the effect in Jamaica.

METHODS

The vaccine effect on rates of hospitalizations and emergency department visits in Jamaica was evaluated in both modified intention-to-treat and per-protocol analyses. Rates of serious adverse events, including intussusception, also were compared between groups.

RESULTS

A total of 1804 Jamaican infants, 6 to 12 weeks of age at entry and primarily from low/middle-income families of African heritage, received ≥1 dose. During the first year after dose 1, there were 2 and 11 hospitalizations or emergency department visits attributable to rotavirus gastroenteritis involving any serotype among 831 evaluable vaccine recipients and 809 evaluable placebo recipients, respectively (rate reduction: 82.2% [95% confidence interval: 15.1%-98.0%]). In the per-protocol analysis, all 8 G1 to G4 rotavirus-attributable events that occurred ≥2 weeks after dose 3 were in the placebo group (rate reduction: 100% [95% confidence interval: 40.9%-100%]). Of the 1802 subjects included in the safety analyses, intussusception was confirmed for 1 vaccine recipient (115 days after the third dose) and 3 placebo recipients. One vaccine recipient and 3 placebo recipients died during the follow-up period, but none of the deaths was considered to be vaccine-related.

CONCLUSIONS

In this posthoc subgroup analysis, the vaccine reduced health care resource utilization attributable to rotavirus gastroenteritis, without increased risk of intussusception or other serious adverse events, among infants in a resource-limited country.

A decade of vaccines: Integrating immunology and vaccinology for rational vaccine design

Vaccination stands as one of the most successful public health measures of the last century. New approaches will be needed, however, to develop highly effective vaccines to prevent tuberculosis, HIV-AIDS, and malaria and to eradicate polio. Current advances in immunology and technology have set the stage for rational vaccine design to begin a "Decade of Vaccines."

Global impact of rotavirus vaccines

The WHO has recently recommended the inclusion of rotavirus vaccine in the national immunization programs of all countries. In countries in the Americas, Europe and Australia that have adopted routine childhood immunization against rotavirus, significant reductions in the burden of severe childhood diarrhea have been observed. Besides protecting vaccinated children, disease rates also appear to be reduced in unvaccinated children, suggesting indirect benefits from vaccination (i.e., herd protection). Early clinical trial data from Africa and Asia are promising, and further efforts are needed to optimize the benefits of vaccination in developing countries where vaccines are likely to have their greatest impact.

[Toward the elimination of rotavirus gastroenteritis by universal vaccination]

Rotavirus is the most important cause of severe gastroenteritis in children worldwide, and is most effectively controlled by vaccines. The Strategic Advisory Group of Experts (SAGE) of the World Health Organization (WHO) recommended, in 2009, the inclusion of rotavirus vaccination of infants into all national immunization programs. Two, live, orally-administrable vaccines are licensed globally. They are Rotarix, a G1P[8] monovalent, human rotavirus-based vaccine (GlaxoSmithKline), and RotaTeq, a pentavalent, bovine-human reassortant vaccine (Merck). Although the two vaccines are very different in antigenic composition and administration schedule, they are almost equally safe with respect to intussusception and 90-100% efficacious against severe rotavirus diarrhea. Countries where either vaccine was introduced into the national childhood immunization program have witnessed not only a drastic decrease in the number of rotavirus hospitalizations but a near 50% reduction in the number of all-cause-diarrhea hospitalizations. Rotavirus diarrhea, an emerging infectious disease because of its discovery in 1973, may now be among vaccine preventable diseases.

Improving the performance of enteric vaccines in the developing world

Vaccines against important enteric pathogens such as rotavirus and poliovirus have shown lower efficacy in some populations. The application of new technologies and diverse scientific disciplines are needed to realize the promise of truly universal and effective solutions to combat those and other enteric diseases.

Pentavalent rotavirus vaccine and prevention of gastroenteritis hospitalizations in Australia

OBJECTIVE

A publicly funded, universal infant pentavalent rotavirus vaccine (RV5) program was implemented in Queensland, Australia, in mid-2007. We sought to assess vaccine effectiveness (VE) of 3 doses of RV5 at preventing rotavirus and nonrotavirus acute gastroenteritis (AGE) hospitalizations in the first birth cohort and impact on hospitalizations in all age groups.

METHODS

Hospitalization rates for rotavirus and nonrotavirus AGE in all age groups before and after RV5 introduction were compared. Population vaccine coverage, hospitalization data, and individual vaccination status were obtained from routinely collected, publicly funded state- and nationally based data sets. Data linkage was performed to calculate 3-dose VE for preventing hospitalization in the eligible age group.

RESULTS

RV5 coverage in the first eligible birth cohort was 89.6% for at least 1 dose and 73.1% for 3 doses. Three-dose VE for preventing nonrotavirus AGE hospitalization was 62.3% to 63.9% (any/primary diagnosis) and 89.3% to 93.9% (any/primary diagnosis) for rotavirus hospitalizations. After program implementation, there were immediate and sustained reductions in rotavirus hospitalizations for those who were younger than 20 years and nonrotavirus AGE-coded hospitalizations for those who were younger than 5 years.

CONCLUSIONS

RV5 is highly effective at preventing rotavirus hospitalizations in a developed country setting, confirming efficacy figures from the pivotal clinical trial. Additional direct and indirect effects are substantial and include reductions in nonrotavirus AGE hospitalizations in vaccinated age groups and rotavirus and nonrotavirus AGE hospitalization rates in older age groups.

Efficacy of pentavalent rotavirus vaccine against severe rotavirus gastroenteritis in infants in developing countries in sub-Saharan Africa: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Rotavirus gastroenteritis causes many deaths in infants in sub-Saharan Africa. Because rotavirus vaccines have proven effective in developed countries but had not been tested in developing countries, we assessed efficacy of a pentavalent rotavirus vaccine against severe disease in Ghana, Kenya, and Mali between April, 2007, and March, 2009.

METHODS

In our multicentre, double-blind, placebo-controlled trial, undertaken in rural areas of Ghana and Kenya and an urban area of Mali, we randomly assigned infants aged 4-12 weeks without symptoms of gastrointestinal disorders in a 1:1 ratio to receive three oral doses of pentavalent rotavirus vaccine 2 mL or placebo at around 6 weeks, 10 weeks, and 14 weeks of age. Infants with HIV infection were not excluded. Randomisation was done by computer-generated randomisation sequence in blocks of six. We obtained data for gastrointestinal symptoms from parents on presentation to health-care facilities and clinical data were obtained prospectively by clinicians. The primary endpoint was severe rotavirus gastroenteritis (Vesikari score >or=11), detected by enzyme immunoassay, arising 14 days or more after the third dose of placebo or vaccine to end of study (March 31, 2009; around 21 months of age). Analysis was per protocol; infants who received scheduled doses of vaccine or placebo without intervening laboratory-confirmed naturally occurring rotavirus disease earlier than 14 days after the third dose and had complete clinical and laboratory results were included in the analysis. This study is registered with ClinicalTrials.gov, number NCT00362648.

FINDINGS

5468 infants were randomly assigned to receive pentavalent rotavirus vaccine (n=2733) or placebo (n=2735). 2357 infants assigned to vaccine and 2348 assigned to placebo were included in the per-protocol analysis. 79 cases of severe rotavirus gastroenteritis were reported in 2610.6 person-years in the vaccine group, compared with 129 cases in 2585.9 person-years in the placebo group, resulting in a vaccine efficacy against severe rotavirus gastroenteritis of 39.3% (95% CI 19.1-54.7, p=0.0003 for efficacy >0%). Median follow-up in both groups was 527 days starting 14 days after the third dose of vaccine or placebo was given. 42 (1.5%) of 2723 infants assigned to receive vaccine and 45 (1.7%) of 2724 infants assigned to receive placebo had a serious adverse event within 14 days of any dose. The most frequent serious adverse event was gastroenteritis (vaccine 17 [0.6%]; placebo 17 [0.6%]).

INTERPRETATION

Pentavalent rotavirus vaccine is effective against severe rotavirus gastroenteritis in the first 2 years of life in African countries with high mortality in infants younger than 5 years. We support WHO's recommendation for adoption of rotavirus vaccine into national expanded programmes on immunisation in Africa.

FUNDING

PATH (GAVI Alliance grant) and Merck.

Rotavirus infections and vaccines: burden of illness and potential impact of vaccination

Rotaviruses are the most common cause of severe gastroenteritis in children. By 5 years of age virtually every child worldwide will have experienced at least one rotavirus infection. This leads to an enormous disease burden, where every minute a child dies because of rotavirus infection and another four are hospitalized, at an annual societal cost in 2007 of $US2 billion. Most of the annual 527 000 deaths are in malnourished infants living in rural regions of low and middle income countries. In contrast, most measurable costs arise from medical expenses and lost parental wages in high income countries. Vaccines are the only public health prevention strategy likely to control rotavirus disease. They were developed to mimic the immunity following natural rotavirus infection that confers protection against severe gastroenteritis and consequently reduces the risk of primary healthcare utilization, hospitalization and death. The two currently licensed vaccines--one a single human strain rotavirus vaccine, the other a multiple strain human-bovine pentavalent reassortant rotavirus vaccine--are administered to infants in a two- or three-dose course, respectively, with the first dose given at 6-14 weeks of age. In various settings they are safe, immunogenic and efficacious against many different rotavirus genotypes. In high and middle income countries, rotavirus vaccines confer 85-100% protection against severe disease, while in low income regions of Africa and Asia, protection is less, at 46-77%. Despite this reduced efficacy in low income countries, the high burden of diarrheal disease in these regions means that proportionately more severe cases are prevented by vaccination than elsewhere. Post-licensure effectiveness studies show that rotavirus vaccines not only reduce rotavirus activity in infancy but they also decrease rates of rotavirus diarrhea in older and unimmunized children. A successful rotavirus vaccination program will rely upon sustained vaccine efficacy against diverse and evolving rotavirus strains and efficient vaccine delivery systems. The potential introduction of rotavirus vaccines into the world's poorest countries with the greatest rates of rotavirus-related mortality is expected to be very cost effective, while rotavirus vaccines should also be cost effective by international standards when incorporated into developed countries immunization schedules. Nonetheless, cost effectiveness in each country still depends largely on the local rotavirus mortality rate and the price of the vaccine in relation to the per capita gross domestic product.

Vaccines for preventing rotavirus diarrhoea: vaccines in use

BACKGROUND

Rotavirus results in higher diarrhoea-related death in children less than five years of age than any other single agent, particularly in low- and middle-income countries. The World Health Organization has recommended the use of rotavirus vaccines in childhood immunization schedules.

OBJECTIVES

To evaluate rotavirus vaccines approved for use (Rotarix, RotaTeq, and Lanzhou Lamb Rotavirus (LLR)) for preventing rotavirus diarrhoea.

SEARCH STRATEGY

In February 2010, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (published in The Cochrane Library 2009, Issue 1), MEDLINE, EMBASE, LILACS, and BIOSIS. We also searched the ICTRP (January 2010) and checked reference lists of identified studies.

SELECTION CRITERIA

Randomized controlled trials comparing rotavirus vaccines approved for use with placebo, no intervention, or another vaccine in children.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility, extracted data, and assessed risk of bias. Dichotomous data were combined using the risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

Thirty-four trials that included 175,944 participants met the inclusion criteria. They evaluated Rotarix (26 trials; 99,841 participants) and RotaTeq (eight trials; 76,103 participants), and had variable risk of bias (where information provided). None of the identified trials used LLR or compared rotavirus vaccines. Compared to placebo, Rotarix and RotaTeq were both effective at reducing rotavirus diarrhoea (severe cases and cases of any severity). They also reduced all-cause diarrhoea (severe cases), and hospitalizations and need for medical attention caused by rotavirus diarrhoea. However, few data were available for Rotarix and all-cause diarrhoea. Versus the placebo groups, participants in each vaccine group had similar numbers of deaths, serious adverse events, reactogenicity profiles (fever, diarrhoea, and vomiting), and adverse events that required discontinuation of the vaccination schedule. Both vaccines were immunogenic (measured by virus shedding in stool and/or seroconversion). Subgroup analyses indicate that both vaccines are effective in countries with different incomes, but few data are available.

AUTHORS' CONCLUSIONS

Rotarix and RotaTeq are effective vaccines for the prevention of rotavirus diarrhoea. The balance between benefit and harm favours benefit. Ongoing safety monitoring should be continued. Trials comparing LLR with placebo should be conducted and the results made available.