A. Duncan Steele

2008 estimate of worldwide rotavirus-associated mortality in children younger than 5 years before the introduction of universal rotavirus vaccination programmes: a systematic review and meta-analysis

BACKGROUND WHO recommends routine use of rotavirus vaccines in all countries, particularly in those with high mortality attributable to diarrhoeal diseases. To establish the burden of life-threatening rotavirus disease before the introduction of a rotavirus vaccine, we aimed to update the estimated number of deaths worldwide in children younger than 5 years due to diarrhoea attributable to rotavirus infection. METHODS We used PubMed to identify studies of at least 100 children younger than 5 years who had been admitted to hospital with diarrhoea. Additionally, we required the studies to have a data collection midpoint of the year 2000 or later, to be done in full-year increments, and to assesses diarrhoea attributable to rotavirus with EIAs or polyacrylamide gel electrophoresis. We also included data from countries that participated in the WHO-coordinated Global Rotavirus Surveillance Network (consisting of participating member states during 2009) and that met study criteria. For countries that have introduced a rotavirus vaccine into their national immunisation programmes, we excluded data subsequent to the introduction. We classified studies into one of five groups on the basis of region and the level of child mortality in the country in which the study was done. For each group, to obtain estimates of rotavirus-associated mortality, we multiplied the random-effect mean rotavirus detection rate by the 2008 diarrhoea-related mortality figures for countries in that group. We derived the worldwide mortality estimate by summing our regional estimates. FINDINGS Worldwide in 2008, diarrhoea attributable to rotavirus infection resulted in 453,000 deaths (95% CI 420,000-494,000) in children younger than 5 years-37% of deaths attributable to diarrhoea and 5% of all deaths in children younger than 5 years. Five countries accounted for more than half of all deaths attributable to rotavirus infection: Democratic Republic of the Congo, Ethiopia, India, Nigeria, and Pakistan; India alone accounted for 22% of deaths (98,621 deaths). INTERPRETATION Introduction of effective and available rotavirus vaccines could substantially affect worldwide deaths attributable to diarrhoea. Our new estimates can be used to advocate for rotavirus vaccine introduction and to monitor the effect of vaccination on mortality once introduced.

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

BACKGROUND Rotavirus vaccine has proved effective for prevention of severe rotavirus gastroenteritis in infants in developed countries, but no efficacy studies have been done in developing countries in Asia. We assessed the clinical efficacy of live oral pentavalent rotavirus vaccine for prevention of severe rotavirus gastroenteritis in infants in Bangladesh and Vietnam. METHODS In this multicentre, double-blind, placebo-controlled trial, undertaken in rural Matlab, Bangladesh, and urban and periurban Nha Trang, Vietnam, infants aged 4-12 weeks without symptoms of gastrointestinal disorders were randomly assigned (1:1) to receive three oral doses of pentavalent rotavirus vaccine 2 mL or placebo at around 6 weeks, 10 weeks, and 14 weeks of age, in conjunction with routine infant vaccines including oral poliovirus vaccine. Randomisation was done by computer-generated randomisation sequence in blocks of six. Episodes of gastroenteritis in infants who presented to study medical facilities were reported by clinical staff and from parent recollection. The primary endpoint was severe rotavirus gastroenteritis (Vesikari score >or=11) 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 2036 infants were randomly assigned to receive pentavalent rotavirus vaccine (n=1018) or placebo (n=1018). 991 infants assigned to pentavalent rotavirus vaccine and 978 assigned to placebo were included in the per-protocol analysis. Median follow up from 14 days after the third dose of placebo or vaccine until final disposition was 498 days (IQR 480-575). 38 cases of severe rotavirus gastroenteritis (Vesikari score >or=11) were reported during more than 1197 person-years of follow up in the vaccine group, compared with 71 cases in more than 1156 person years in the placebo group, resulting in a vaccine efficacy of 48.3% (95% CI 22.3-66.1) against severe disease (p=0.0005 for efficacy >0%) during nearly 2 years of follow-up. 25 (2.5%) of 1017 infants assigned to receive vaccine and 20 (2.0%) of 1018 assigned to receive placebo had a serious adverse event within 14 days of any dose. The most frequent serious adverse event was pneumonia (vaccine 12 [1.2%]; placebo 15 [1.5%]). INTERPRETATION In infants in developing countries in Asia, pentavalent rotavirus vaccine is safe and efficacious against severe rotavirus gastroenteritis, and our results support expanded WHO recommendations to promote its global use. FUNDING PATH (GAVI Alliance grant) and Merck.

Systematic review of regional and temporal trends in global rotavirus strain diversity in the pre rotavirus vaccine era: insights for understanding the impact of rotavirus vaccination programs.

Recently, two rotavirus vaccines have been recommended for routine immunization of infants worldwide. These vaccines proved efficacious during clinical trials and field use in both developing and developed countries, and appear to provide good protection against a range of rotavirus genotypes, including some that are not included in the vaccines. However, since conclusive data that the vaccines will protect against a wide variety of rotavirus strains are still lacking and since vaccines may exert some selection pressure, a detailed picture of global strain prevalence from the pre-rotavirus vaccine era is important to evaluate any potential changes in circulating strains observed after widespread introduction of rotavirus vaccines. Thus, we systematically reviewed rotavirus genotyping studies spanning a 12-year period from 1996 to 2007. In total, ~110,000 strains were genotyped from 100 reporting countries. Five genotypes (G1-G4, and G9) accounted for 88% of all strains, although extensive geographic and temporal differences were observed. For example, the prevalence of G1 strains declined from 2000 onward, while G3 strains re-emerged, and G9 and G12 strains emerged during the same period. When crude strain prevalence data were weighted by region based on the regions contribution to global rotavirus mortality, the importance of genotypes G1 and G9 strains that were more prevalent in regions with low mortality was reduced and conversely the importance of G8 strains that were more prevalent in African settings with greater contribution to global rotavirus mortality was increased. This study provides the most comprehensive, up-to-date information on rotavirus strain surveillance in the pre-rotavirus vaccine era and will provide useful background to examine the impact of rotavirus vaccine introduction on future strain prevalence.

Rotavirus Vaccines: Targeting the Developing World

For the past 2 decades, rotavirus infection, the most common cause of severe diarrhea in children, has been a priority target for vaccine development. This decision to develop rotavirus vaccines is predicated on the great burden associated with fatal rotavirus disease (i.e., 440,000 deaths/year), the firm scientific basis for developing live oral vaccines, the belief that increased investment in development at this time could speed the introduction of vaccines in developing countries, and the appreciation that implementation of a vaccine program should result in a measurable decrease in the number of hospitalizations and deaths associated with rotavirus disease within 2-3 years. RotaShield (Wyeth-Ayerst), the first rotavirus vaccine licensed in the United States, was withdrawn after 9 months because of a rare association of the vaccine with the development of intussusception. In the developing world, this vaccine could still have had a measurable effect, because the benefits of preventing deaths due to rotavirus disease would have been substantially greater than the rare risk of intussusception. Two live oral vaccines being prepared by GlaxoSmithKline and Merck have completed large-scale clinical trials. The GlaxoSmithKline vaccine has been licensed in Mexico and the Dominican Republic, and the Merck vaccine could be licensed in the United States within 1 year; several other candidate vaccines are in earlier stages of testing. However, many challenges remain before any of these vaccines can be incorporated into childhood immunization programs in the developing world. First, vaccine efficacy, which has already been demonstrated in children in industrialized and middle-income countries, needs to be proven in poor developing countries in Africa and Asia. The safety of vaccines with regard to the associated risk of intussusception must be demonstrated as well. Novel financing strategies will be needed to ensure that new vaccines are affordable and available in the developing world. Decision makers and parents in developing countries need to know about this disease that has little name recognition and is rarely diagnosed. Finally, for the global effort toward the prevention of rotavirus disease to be successful, special efforts will be required in India, China, and Indonesia, because one-third of all deaths due to rotavirus disease occur in these countries, and because these countries depend almost entirely on vaccines manufactured domestically.

Burden and epidemiology of rotavirus diarrhea in selected African countries: preliminary results from the African rotavirus surveillance network.

Severe rotavirus diarrhea in children <5 years of age is a major public health problem; however, limited regional and country specific data on rotavirus disease burden are available from sub-Saharan Africa. In June 2006, the World Health Organization Regional Office for Africa initiated rotavirus surveillance in selected African countries. With use of standardized methodology developed by the World Health Organization, children <5 years of age who were hospitalized with severe diarrhea were enrolled, and stool specimens were collected for detection of rotavirus strains with use of a commercial enzyme immunoassay. Rotavirus strains were further characterized for G and P types with use of a reverse-transcriptase polymerase chain reaction. From June 2006 through December 2008, rotavirus surveillance was established at 14 sites in 11 African countries. Of 5461 stool samples collected from children enrolled in 8 countries with 1 or 2 complete years of data, 2200 (40%) were positive for rotavirus. Ninety percent of all rotavirus hospitalizations occurred among children aged 3-12 months. Predominant types included G1P[8] (21%), G2P[4] (7%), and P [8] (29%); however, unusual types were also detected, including G8P[6] (5%), G8P[8] (1%), G12P[6] (1%), and G12P[6] (1%). A high percentage of mixed rotavirus infections was also detected. These preliminary results indicate that rotavirus is a major cause of severe diarrheal disease in African children.

Rotavirus Strain Types Circulating in Africa: Review of Studies Published during 1997–2006

Rotavirus is responsible for more than half a million deaths among infants and young children worldwide each year; many of these deaths could be prevented by widespread use of an effective rotavirus vaccine. The diversity of rotavirus strains in many developing countries, where most rotavirus deaths occur, could represent a significant challenge to the efficacy of current vaccines. In anticipation of rotavirus vaccine introduction, we examined studies published over a 10-year period (1997-2006) from countries in Africa that examined the distribution of VP7 (G) and VP4 (P) rotavirus strain types in symptomatic children and in neonates, together with studies that undertook a more detailed characterization of unusual rotavirus strains. Compared with recently published global reviews of rotavirus strain types and a previous review of the African literature published before 1997, the current data indicate a substantially increased diversity of rotavirus strains across the continent. Notable findings included a reduction in the proportion of globally common serotypes; a high proportion of unusual P/G combinations, suggesting viral reassortment; evidence for zoonotic rotavirus transmission; the emergence and spread across Africa of serotype G9; and a high prevalence of the P[6] VP4 genotype. These data imply that rotavirus vaccines will need to confer protection against a wide variety of strain types in Africa and emphasize the importance of continued strain surveillance before and after the introduction of routine rotavirus vaccination.

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.

Efficacy of human rotavirus vaccine against severe gastroenteritis in Malawian children in the first two years of life: a randomized, double-blind, placebo controlled trial.

Rotavirus gastroenteritis is a major cause of morbidity and mortality among African infants and young children. A phase III, placebo-controlled, multi-centre clinical trial of a live, oral G1P[8] human rotavirus vaccine (RIX4414) undertaken in Malawi and South Africa significantly reduced the incidence of severe rotavirus gastroenteritis in the first year of life. We now report on vaccine efficacy in the Malawi cohort of children who were followed into the second year of life. A total of 1773 healthy infants were enrolled in Blantyre, Malawi into three groups. Two groups received three doses of RIX4414 or placebo at age 6, 10, and 14 weeks and the third group received placebo at 6 weeks and RIX4414 at age 10 and 14 weeks. Subjects were followed by weekly home visits for episodes of gastroenteritis until 1 year of age, and were then re-consented for further follow-up to 18-24 months of age. Severity of gastroenteritis episodes was graded according to the Vesikari scoring system. Seroconversion for anti-rotavirus IgA was determined on a subset of children by using ELISA on pre- and post-vaccine blood samples. Rotavirus VP7 (G) and VP4 (P) genotypes were determined by RT-PCR. A total of 70/1030 (6.8%, 95% CI 5.3-8.5) subjects in the pooled (2 dose plus 3 dose) RIX4414 group compared with 53/483 (11.0%, 8.3-14.1) subjects in the placebo group developed severe rotavirus gastroenteritis in the entire follow-up period (vaccine efficacy 38.1% (9.8-57.3)). The point estimate of efficacy in the second year of life (17.6%; -59.2 to 56.0) was lower than in the first year of life (49.4%; 19.2-68.3). There were non-significant trends towards a higher efficacy in the second year of life among children who received the three-dose schedule compared with the two-dose schedule, and a higher anti-rotavirus IgA seroresponse rate in the three-dose RIX4414 group. Rotavirus strains detected included genotype G12 (31%); G9 (23%); and G8 (18%); only 18% of strains belonged to the G1P[8] genotype. While the optimal dosing schedule of RIX4414 in African infants requires further investigation, vaccination with RIX4414 significantly reduced the incidence of severe gastroenteritis caused by diverse rotavirus strains in an impoverished African population with high rotavirus disease burden in the first two years of life.

Efficacy and safety of a live attenuated influenza vaccine in adults 60 years of age and older.

This randomized, double-blind, placebo-controlled study investigated the efficacy, safety, and immunogenicity of LAIV in community-dwelling ambulatory adults > or =60 years of age in South Africa in 2001. Nose and throat swabs were obtained for influenza virus culture based on the symptoms of influenza-like illness. A total of 3242 subjects were enrolled, with a mean age of 69.5 years. The efficacy of LAIV against influenza viruses antigenically similar to the vaccine was 42.3% (95% CI, 21.6-57.8%). Efficacy against A/H3N2 viruses was 52.5% (95% CI, 32.1-67.2%); vaccine efficacy was not observed against antigenically similar B strains. In post hoc analyses, efficacy in subjects 60 to <70 years of age was 41.8% and -22.7% against A/H3N2 and B, respectively and 65.7% and 9.9%, respectively, for subjects > or =70 years. Reactogenicity events were higher among LAIV than placebo recipients during 11 days postvaccination (P=0.042), including runny nose/nasal congestion, cough, sore throat, headache, muscle aches, tiredness, and decreased appetite. Rates of serious adverse events were similar for LAIV and placebo recipients. This was the first demonstration of statistically significant protection by LAIV against culture-confirmed influenza in adults > or =60 years of age. These results suggest that LAIV may provide an additional public health tool in the prevention of influenza in the elderly. (ClinicalTrials.gov identifier, NCT00217230.).

Update on Rotavirus Vaccines

Rotavirus was discovered in 1973, and 10 years later the first report of a rotavirus vaccine clinical trial appeared. This update reviews the epidemiology of rotavirus infections, assesses past and current vaccines and presents ideas for implementation of vaccination programs in developed and developing countries.