Predominance of rotavirus G1[P8] genotype among under-five children with gastroenteritis in Mwanza, Tanzania

Genetic Profile of Rotavirus Type A in Children under 5 Years Old in Africa: A Systematic Review of Prevalence

Human type A rotavirus (RV-A) is world-recognized as the major pathogen causing viral gastroenteritis in children under 5 years of age. The literature indicates a substantial increase in the diversity of rotavirus strains across continents, especially in Africa, which can pose significant challenges including an increase of disease burden and a reduction of vaccines' effectiveness. However, few studies have mapped the variety of circulating virus strains in different regions, which may hamper decisions on epidemiological surveillance and preventive public health measures. Thus, our aim was to compile the most updated available evidence on the genetic profile of RV-A among children in Africa and determine the prevalence of different genotypes according to the geographical regions by means of a broad systematic review. Systematic searches were performed in PubMed, Scopus, Web of Science, and Scielo without language, time limits, or geographical restrictions within the African continent. We selected full-text peer-reviewed articles assessing the genetic profile (i.e., genotyping) of RV-A in children up to 5 years old in Africa. Overall, 682 records were retrieved, resulting in 75 studies included for evidence synthesis. These studies were published between 1999 and 2022, were conducted in 28 countries from the five African regions, and 48% of the studies were carried out for 24 months or more. Most studies (n = 55; 73.3%) evaluated RV-A cases before the introduction of the vaccines, while around 20% of studies (n = 13) presented data after the vaccine approval in each country. Only seven (9.3%) studies compared evidence from both periods (pre- and post-vaccine introduction). Genotyping methods to assess RV-A varied between RT-PCR, nested or multiplex RT-PCR, testing only the most common P and G-types. We observed G1 and P[8] to be the most prevalent strains in Africa, with values around 31% and 43%, respectively. Yet if all the genotypes with the following highest prevalence were added ((G1 + G2, G3, G9) and (P[8] + P[6], P[4])), these figures would represent 80% and 99% of the total prevalence. The combination G1P[8] was the most reported in the studies (around 22%). This review study demonstrated an increased strain diversity in the past two decades, which could represent a challenge to the efficacy of the current vaccine.

Rotavirus genotype diversity in Tanzania during Rotavirus vaccine implementation between 2013 and 2018

The study aims to determine Rotavirus genotypes between 2013 and 2018 during implementation of ROTARIX vaccine in Tanzania. The analysis of surveillance data obtained between 2013 and 2018 was done to determine circulating genotypes after introduction of Rotarix vaccine. From 2013 to 2018, a total of 10,557 samples were collected and screened for Rotavirus using an enzyme immunoassay. A significant decrease in Rotavirus positivity (29.3% to 17.8%) from 2013 to 2018 (OR 0.830, 95% CI 0.803-0.857, P < 0.001) was observed. A total of 766 randomly selected Rotavirus positive samples were genotyped. Between 2013 and 2018, a total of 18 Rotavirus genotypes were detected with G1P [8] being the most prevalent. The G1P [8] strain was found to decrease from 72.3% in 2015 to 13.5% in 2018 while the G9P [4] strain increased from 1 to 67.7% in the same years. G2P [4] was found to decrease from 59.7% in 2013 to 6.8% in 2018 while G3P [6] decreased from 11.2% in 2014 to 4.1% in 2018. The data has clearly demonstrated that ROTARIX vaccine has provided protection to varieties of the wild-type Rotavirus strains. Continuous surveillance is needed to monitor the circulation of Rotavirus strains during this era of vaccine implementation.

Genetic diversity and Genomic analysis of G3P[6] and equine-like G3P[8] in Children Under-five from Southern Highlands and Eastern Tanzania

Rotavirus group A genomic characterization is critical for understanding the mechanisms of rotavirus diversity, such as reassortment events and possible interspecies transmission. However, little is known about the genetic diversity and genomic relationship of the rotavirus group A strains circulating in Tanzania. The genetic and genomic relationship of RVA genotypes was investigated in children under the age of five. A total of 169 faecal samples were collected from under-five with diarrhea in Mbeya, Iringa and Morogoro regions of Tanzania. The RVA were screened in children under five with diarrhea using reverse transcription PCR for VP7 and VP4, and the G and P genotypes were determined using Sanger dideoxynucleotide cycle sequencing. Whole-genome sequencing was performed on selected genotypes. The overall RVA rate was 4.7% (8/169). The G genotypes were G3 (7/8) and G6 (1/8) among the 8 RVA positives, while the P genotypes were P[6] (4/8) and P[8] (2), and the other two were untypeable. G3P[6] and G3P[8] were the identified genotype combinations. The genomic analysis reveals that the circulating G3P[8] and G3P[6] isolates from children under the age of five with diarrhea had a DS-1-like genome configuration (I2-R2-C2-M2-Ax-N2-T2-E2-H2). The phylogenic analysis revealed that all 11 segments of G3P[6] were closely related to human G3P[6] identified in neighboring countries such as Uganda, Kenya, and other African countries, implying that G3P[6] strains descended from a common ancestor. Whereas, G3P[8] were closely related to previously identified equine-like G3P[P8] from Kenya, Japan, Thailand, Brazil, and Taiwan, implying that this strain was introduced rather than reassortment events. We discovered amino acid differences at antigenic epitopes and N-linked glycosylation sites between the wild type G3 and P[8] compared to vaccine strains, implying that further research into the impact of these differences on vaccine effectiveness is warranted. The phylogenic analysis of VP7 also identified a bovine-like G6. For the first time in Tanzania, we report the emergence of novel equine-like G3 and bovine-like G6 RVA strains, highlighting the importance of rotavirus genotype monitoring and genomic analysis of representative genotypes.

Adenovirus Infection Is Predicted by Prolonged Duration of Diarrhea among Rotavirus-Vaccinated Children below Five Years of Age in Mwanza, Tanzania

Diarrhea is the commonest cause of morbidity and mortality in many resource-limited countries including Tanzania among children below five years of age. A significant number of diarrhea cases associated with severe dehydration are still being reported among children despite five years of rotavirus vaccine implementation in Tanzania necessitating the need to investigate other causes of diarrhea in this population. This study is aimed at determining the prevalence of human adenovirus infection and associated factors among rotavirus-vaccinated children with acute diarrhea in Mwanza, Tanzania. A cross-sectional study was conducted from June to August 2017 involving 137 children less than two years of age admitted with acute diarrhea in the health facilities located in Mwanza, Tanzania. Sociodemographic and other relevant information were collected using standardized rotavirus surveillance tool adopted from WHO. Stool specimens were collected and tested for human adenovirus antigen using immunochromatographic tests. Data were analyzed by using STATA version 13. The median age of enrolled children was 12 (IQR 8-17) months. The prevalence of human adenovirus was found to be 46 (33.6%, 95% CI: 25-41). By multivariable logistic regression analysis, only prolonged duration of diarrhea (OR: 1.619, 95% CI: 1.142-2.295, p = 0.007) was found to predict human adenovirus infection among rotavirus-vaccinated children with acute diarrhea. A significant proportion of rotavirus-vaccinated children with prolonged acute diarrhea have adenovirus infection. There is a need to consider other viral pathogens as potential cause of diarrhea especially in this postrotavirus vaccination period.

Distribution of rotavirus genotypes in Japan from 2015 to 2018: Diversity in genotypes before and after introduction of rotavirus vaccines

BACKGROUND

Diversity in group A rotavirus (RVA) strains after introduction of RV-vaccines remains an emerging concern worldwide. In this study, we investigated the prevalence and distribution of RVA genotypes in Japanese children with acute gastroenteritis (AGE) from 2015 to 2018. In addition, a comparison of the genotypes in pre-vaccination (2006-2012) and post-vaccination (2012-2018) periods was conducted to understand the impact of these vaccines on genotype distribution.

METHODS

Fecal samples were collected regularly from outpatient clinics in six localities: Hokkaido, Tokyo, Shizuoka, Osaka, Kyoto, and Saga. RVA were screened and genotyped by RT-PCR and sequence-based genotyping.

RESULTS

During the period 2015-2018, RVA was detected in 307 (19.7%) samples out of 1557 specimens: 29.9% (95% CI: 25.8% to 34.3%), 17.9% (95% CI: 14.7% to 21.5%), and 13% (95% CI: 10.3% to 16.0%) were detected RVA-positive in 2015-2016, 2016-2017 and 2017-2018, respectively. The average detection of RVA in pre-vaccination (2006-2012) and post-vaccination (2012-2018) era remained almost similar (18%-20%). The G2P[4]I2 (52.1%, 95% CI: 43.5%-60.6%) remained the most common genotype in 2015-2016, whereas G8P[8]I2 (55.9%, 95% CI: 45.2%-66.2%) dominated in 2016-2017. In 2017-2018, G9P[8]I2 (42.0%, 95% CI: 30.5%-53.9%) prevailed, followed by G9P[8]I1 (23.0%, 95% CI: 14.0%-34.2%). The detection rate of some common genotypes of pre-vaccination era like G1P[8] and G3P[8] has been reduced after introduction of RV-vaccine, whereas genotypes that were sporadic before the introduction of vaccines like G2P[4], G2P[8], G9P[8] and G8P[8] were emerged/reemerged in post-vaccination period.

CONCLUSIONS

Our study presented the diversity in circulating RVA genotypes in Japan before and after introduction of RV-vaccines. Sudden emergence of DS-1-like (I2) unusual strains in post-vaccination era remains alarming. Continuous monitoring of RVA genotypes is therefore indispensable to refine future vaccine strategy.

Rotavirus Burden, Genetic Diversity and Impact of Vaccine in Children under Five in Tanzania

In Tanzania, rotavirus infections are responsible for 72% of diarrhea deaths in children under five. The Rotarix vaccine was introduced in early 2013 to mitigate rotavirus infections. Understanding the disease burden and virus genotype trends over time is important for assessing the impact of rotavirus vaccine in Tanzania. When assessing the data for this review, we found that deaths of children under five declined after vaccine introduction, from 8171/11,391 (72% of diarrhea deaths) in 2008 to 2552/7087 (36% of diarrhea deaths) in 2013. Prior to vaccination, the prevalence of rotavirus infections in children under five was 18.1–43.4%, 9.8–51%, and 29–41% in Dar es Salaam, Mwanza and Tanga, respectively, and after the introduction of vaccines, these percentages declined to 17.4–23.5%, 16–19%, and 10–29%, respectively. Rotaviruses in Tanzania are highly diverse, and include genotypes of animal origin in children under five. Of the genotypes, 10%, 28%, and 7% of the strains are untypable in Dar es Salaam, Tanga, and Zanzibar, respectively. Mixed rotavirus genotype infection accounts for 31%, 29%, and 12% of genotypes in Mwanza, Tanga and Zanzibar, respectively. The vaccine effectiveness ranges between 53% and 75% in Mwanza, Manyara and Zanzibar. Rotavirus vaccination has successfully reduced the rotavirus burden in Tanzania; however, further studies are needed to better understand the relationship between the wildtype strain and the vaccine strain as well as the zoonotic potential of rotavirus in the post-vaccine era.

Whole genome analyses of DS-1-like Rotavirus A strains detected in children with acute diarrhoea in southern Mozambique suggest several reassortment events

We report the first whole genome constellations of Mozambican rotavirus A strains detected between 2012 and 2013 in the Mavalane General Hospital in Maputo city and Manhiça District Hospital in the Manhiça district. Consensus sequences for ten DS-1-like strains (G2P[4] and G8P[4]) were identified with an Illumina Miseq platform using cDNA prepared from dsRNA extracted from stool samples, without genome amplification or prior adaptation to cell culture. Comparison of previously reported genotyping results and the consensus sequences described in this study, indicated that the genotype primers specific for G12 and P[4] might require revision. Phylogenetic analyses indicated diversity among the G2P[4] Mozambican strains and suggested reassortment between G2P[4] and G8P[4] Mozambican strains, as well as the intragenogroup reassortment of all the genome segments encoding VP1, 2, 3 and 6 for strain RVA/Human-wt/MOZ/0045/2012G8P[4]. These results highlight the necessity to determine whole genome constellations to confirm surveillance data in Africa and to monitor the growing diversity in DS-1-like strains.

Prevalence and Factors Associated with Diarrhoea among Children between 6 and 59 Months of Age in Mwanza City Tanzania

BACKGROUND

Childhood diarrhoea is a global public health problem especially in unplanned settlements of low- and middle-income countries. Different studies have associated household settlement and childhood diarrhoea, but the prevalence and risk factors associated with childhood diarrhoea at the community level are not clearly known.

METHOD

A community-based cross-sectional study was performed to determine the prevalence and risk factors associated with diarrhoea in among 480 children between 6 and 59 months of age in Mwanza city from June to August 2016. Risk factors associated with childhood diarrhoea in Mwanza city were determined using univariate, bivariate and multivariate analysis.

RESULTS

The study showed a prevalence of diarrhoea of 20.4% and an association between type of settlement and childhood diarrhoea (p < 0.001) in a chi-square analysis. During bivariate analysis, and logistic regression, after controlling for other factors, unplanned settlement was significantly associated with childhood diarrhoea (odds ratio=3.475, p < 0.001 and AOR=3.469, p < 0.001). Other factors associated with childhood diarrhoea were behaviour of mother washing hands before preparing food (AOR = 0, 193, p < 0.001), mother washing hands after changing child's napkins (AOR = 0.544, p < 0.036) and the behaviour of the child washing hands after toilet (AOR = 0.447, p < 0.006).

CONCLUSION

Risk factors associated with childhood diarrhoea in Mwanza city are unplanned settlement and behaviour of mother and child washing hands during critical time; hence, continuous community health promotion insisting on washing hands with soap and water during critically time is the best method for fighting childhood diarrhoea in Mwanza city.

Detection of rotavirus before and after monovalent rotavirus vaccine introduction and vaccine effectiveness among children in mainland Tanzania

BACKGROUND

Monovalent rotavirus vaccine (RV1) was introduced in Tanzania in January 2013 under the Reach Every Child initiative, to be given at ages 6 and 10 weeks. We used the sentinel hospital rotavirus surveillance system to examine the rotavirus detection rate before and after vaccine introduction and estimate vaccine effectiveness.

METHODS

Before vaccine introduction, rotavirus surveillance was established at two mainland hospitals; children admitted for acute diarrhea were eligible for enrollment and stools were tested for rotavirus antigen. We compared the rotavirus positivity rate in the pre-vaccine period (Tanga Hospital, 2009 and 2011; Bugando Medical Centre, 2012) to that from post-introduction years, 2014-2015. In 2013, surveillance was established at 9 additional hospitals. We examined rotavirus positivity among infants at these sites for 2014-2015. We obtained vaccine records and calculated vaccine effectiveness at 3 sites using case-test-negative control design.

RESULTS

At Tanga Hospital, the rotavirus positivity rate among infants was 41% (102/251) pre-vaccine and 14% (28/197) in post-vaccine years (rate ratio: 0.35 [95% CI 0.22-0.54]). At Bugando, the positivity rate was 58% (83/143) pre-vaccine, and 18% (49/277) post-introduction (rate ratio 0.30 [95% CI 0.210.44]). Results were similar among children <5 years. At the new sites, the median site rotavirus positivity rate among infants was 26% in 2014 (range 19-44%) and 18% in 2015 (range 16-33%). The effectiveness of ≥1 RV1 dose against rotavirus hospitalization among children 5-23 months was 53% (95% CI: -14, 81), and 66% (95% CI: 9-87) against hospitalization with intravenous rehydration. Following introduction, peak rotavirus activity occurred later in the year and appeared more concentrated in time.

CONCLUSION

Rotavirus surveillance data from Tanzania indicate that the rotavirus positivity rate among children hospitalized with diarrhea that were enrolled was substantially reduced after vaccine introduction. Low positivity rates among infants were detected at hospitals across the country. Overall, the data support that rotavirus vaccine has been successfully introduced and is effective in Tanzanian children.

Molecular Epidemiology of Rotavirus in Children under Five in Africa (2006-2016): A Systematic Review

Group A human rotaviruses (RVA) are the most common causes of severe viral gastroenteritis in infants and young children worldwide. The available vaccines, while effective in Europe and North America have shown a reduced efficacy in Africa. One issue raised is the genetic variability of RVA. The objective of this study was to perform a literature review of molecular epidemiology to determine the prevalence of RVA genotypes circulating in Africa so as to establish a mapping of reliable data on these various genotypes. The search for articles was done from the National Institutes of Health (PUBMED) using three set of keywords. Articles were selected with inclusion criteria such as the date of publication, the age of the children, the sample size and the diagnostic techniques (standardized laboratory techniques). The data were imported into STATA SE version 11 software. Specific prevalence was estimated with Confidence Intervals (CI) of 95%. A total of 326 published studies were initially retrieved, out of which 27 studies were finally selected for the systematic review. The selected studies cover 20 African countries. The most encountered genotypes in Africa during this period were G1 (32.72%), followed by G2 (17.17%), G3 (9.88%), G9 (8.61%) and G12 (7.56%) among the G-types. The most common P-types were P[8] (48.71%) followed by P[6] (22.60%) and P[4] (11.58%) and the G1P[8] combination (22.64%) was the most encountered followed by G2P[4] (8.29%), G9P[8] (6.95%) and G2P[6] (5.00%). North Africa presented the highest prevalence of the P[8] genotype (65.70%). This review provides a comprehensive view of the current circulating rotavirus strains in Africa, which can be important in light of the new rotavirus vaccinations. Indeed, in Africa, the pursuit of national and continental studies for epidemiological surveillance of circulating rotavirus strains is vital for the promotion of future successful vaccines.

Role of rotavirus vaccination on an emerging G8P[8] rotavirus strain causing an outbreak in central Japan

BACKGROUND

In this study, we examined the effectiveness of RV1 and RV5 vaccines during an outbreak of G8P[8] rotavirus group A strain (G8P[8]-RVA). These vaccines were originally designed to provide protection against severe diseases caused by common circulating strains, whereas G8P[8]-RVA remains emerging strain and partially heterotypic to the vaccines. It is imperative to investigate vaccine effectiveness (VE) against G8P[8]-RVA because this strain appears to be predominant in recent years, particularly, in post-vaccine era.

METHODS

RVA infection and genotypes were confirmed by polymerase chain reaction (PCR) followed by sequence-based genotyping. VE was determined during an outbreak of G8P[8]-RVA in Shizuoka Prefecture, Japan, in February-July 2017, retrospectively, by comparing vaccination status of children suffering from acute gastroenteritis (AGE) between 'PCR-positive' and 'PCR-negative' cases using conditional logistic regression adjusted for age.

RESULTS

Among 80 AGE children, RVA was detected in 58 (73%), of which 53 (66%) was G8P[8]-RVA. The clinical characteristics of G8P[8]-RVA and other RVA strains were identically severe. Notably, the attack rates of G8P[8]-RVA in vaccinated (61.1%) and unvaccinated (65.5%) children were almost similar. Indeed, no substantial effectiveness were found against G8P[8]-RVA (VE, 14% [95% CI: -140% to 70%]) or other RVA strains (VE, 58% [95% CI: -20% to 90%]) for mild infections. However, these vaccines remained strongly effective against moderate (VE, 75% [95% CI: 1% to 40%]) and severe (VE, 92% [95% CI: 60% to 98%]) RVA infections. The disease severity including Vesikari score, duration and frequency of diarrhea, and body temperature were significantly lower in vaccinated children.

CONCLUSIONS

This study demonstrates the effectiveness of current RV vaccines against moderate and severe, but not against the mild infections during an outbreak caused by unusual G8P[8]-RVA, which was virtually not targeted in the vaccines.

Whole genome detection of rotavirus mixed infections in human, porcine and bovine samples co-infected with various rotavirus strains collected from sub-Saharan Africa

Group A rotaviruses (RVA) are among the main global causes of severe diarrhea in children under the age of 5years. Strain diversity, mixed infections and untypeable RVA strains are frequently reported in Africa. We analysed rotavirus-positive human stool samples (n=13) obtained from hospitalised children under the age of 5years who presented with acute gastroenteritis at sentinel hospital sites in six African countries, as well as bovine and porcine stool samples (n=1 each), to gain insights into rotavirus diversity and evolution. Polyacrylamide gel electrophoresis (PAGE) analysis and genotyping with G-(VP7) and P-specific (VP4) typing primers suggested that 13 of the 15 samples contained more than 11 segments and/or mixed G/P genotypes. Full-length amplicons for each segment were generated using RVA-specific primers and sequenced using the Ion Torrent and/or Illumina MiSeq next-generation sequencing platforms. Sequencing detected at least one segment in each sample for which duplicate sequences, often having distinct genotypes, existed. This supported and extended the PAGE and RT-PCR genotyping findings that suggested these samples were collected from individuals that had mixed rotavirus infections. The study reports the first porcine (MRC-DPRU1567) and bovine (MRC-DPRU3010) mixed infections. We also report a unique genome segment 9 (VP7), whose G9 genotype belongs to lineage VI and clusters with porcine reference strains. Previously, African G9 strains have all been in lineage III. Furthermore, additional RVA segments isolated from humans have a clear evolutionary relationship with porcine, bovine and ovine rotavirus sequences, indicating relatively recent interspecies transmission and reassortment. Thus, multiple RVA strains from sub-Saharan Africa are infecting mammalian hosts with unpredictable variations in their gene segment combinations. Whole-genome sequence analyses of mixed RVA strains underscore the considerable diversity of rotavirus sequences and genome segment combinations that result from a complex evolutionary history involving multiple host species.

Dengue and Chikungunya fever among viral diseases in outpatient febrile children in Kilosa district hospital, Tanzania

Introduction

Viral etiologies of fever, including dengue, Chikungunya, influenza, rota and adeno viruses, cause major disease burden in tropical and subtropical countries. The lack of diagnostic facilities in developing countries leads to failure to estimate the true burden of such illnesses, and generally the diseases are underreported. These diseases may have similar symptoms with other causes of acute febrile illnesses including malaria and hence clinical diagnosis without laboratory tests can be difficult. This study aimed to identify viral etiologies as a cause of fever in children and their co-infections with malaria.

Methods

A cross sectional study was conducted for 6 months at Kilosa district hospital, Tanzania. The participants were febrile children aged 2–13 years presented at the outpatient department. Diagnostic tests such as IgM and IgG ELISA, and PCR were used.

Results

A total of 364 patients were enrolled, of these 83(22.8%) had malaria parasites, 76 (20.9%) had presumptive acute dengue infection and among those, 29(38.2%) were confirmed cases. Dengue was more likely to occur in children ≥ 5 years than in <5 years (OR 2.28, 95% CI: 1.35–3.86). Presumptive acute Chikungunya infection was identified in 17(4.7%) of patients. We observed no presenting symptoms that distinguished patients with Chikungunya infection from those with dengue infection or malaria. Co-infections between malaria and Chikungunya, malaria and dengue fever as well as Chikungunya and dengue were detected. Most patients with Chikungunya and dengue infections were treated with antibacterials. Furthermore, our results revealed that 5(5.2%) of patients had influenza virus while 5(12.8%) had rotavirus and 2(5.1%) had adenovirus.

Conclusion

Our results suggest that even though viral diseases are a major public health concern, they are not given due recognition as a cause of fever in febrile patients. Emphasis on laboratory diagnostic tests for proper diagnosis and management of febrile patients is recommended.

Viral etiologies of fever, such as dengue, Chikungunya, influenza, rotaviruses, and adenoviruses contribute to substantial morbidity and mortality particularly in children in the tropical and subtropical countries. Despite their importance, the true burden of viral etiologies of fever in Tanzania is not known, and in most cases these diseases are unrecognized and treated as malaria. This study aimed to identify viral etiologies as a cause of fever in children and co-infections among viral diseases and malaria. A total of 364 febrile children were enrolled, of these, 83 (22.8%) had malaria, 76(20.9%) had presumptive acute dengue, among those, 29(38.2%) were confirmed cases. Dengue was more likely to occur in children aged ≥ 5 years than in <5 years (OR 2.28, 95% CI: 1.35–3.86). Presumptive acute Chikungunya infection was found in 17(4.7%) of patients. Co-infections between malaria and Chikungunya, malaria and dengue as well as Chikungunya and dengue were observed. Furthermore, 5(5.2%) of the patients had influenza virus, 5(12.8%) had rotavirus and 2(5.1%) had adenovirus. Knowledge on occurrence of these viral etiologies of febrile illnesses will alert clinicians to be more responsive towards viral infectious agents as potential causes of febrile illnesses in the routine diagnosis and management of febrile patients.

Review of global rotavirus strain prevalence data from six years post vaccine licensure surveillance: is there evidence of strain selection from vaccine pressure?

Comprehensive reviews of pre licensure rotavirus strain prevalence data indicated the global importance of six rotavirus genotypes, G1P[8], G2P[4], G3P[8], G4P[8], G9P[8] and G12P[8]. Since 2006, two vaccines, the monovalent Rotarix (RV1) and the pentavalent RotaTeq (RV5) have been available in over 100 countries worldwide. Of these, 60 countries have already introduced either RV1 or RV5 in their national immunization programs. Post licensure vaccine effectiveness is closely monitored worldwide. This review aimed at describing the global changes in rotavirus strain prevalence over time. The genotype distribution of the nearly 47,000 strains that were characterized during 2007-2012 showed similar picture to that seen in the preceding period. An intriguing finding was the transient predominance of heterotypic strains, mainly in countries using RV1. Unusual and novel antigen combinations continue to emerge, including some causing local outbreaks, even in vaccinated populations. In addition, vaccine strains have been found in both vaccinated infants and their contacts and there is evidence for genetic interaction between vaccine and wild-type strains. In conclusion, the post-vaccine introduction strain prevalence data do not show any consistent pattern indicative of selection pressure resulting from vaccine use, although the increased detection rate of heterotypic G2P[4] strains in some countries following RV1 vaccination is unusual and this issue requires further monitoring.