Reduction in Severity of All-Cause Gastroenteritis Requiring Hospitalisation in Children Vaccinated against Rotavirus in Malawi

The Application of the Vesikari and Modified Vesikari Severity Scores in Complicated Pediatric Gastroenteritis of Viral Origin: An Observational Study

Background/Objectives: Viral gastroenteritis can have a potentially fatal outcome at young ages and the recognition of severe cases could be aided by clinically derived severity scores. Methods: This observational study intended to conduct a comparative assessment of the utility of the Vesikari and modified Vesikari score in the evaluation of viral gastroenteritis severity and for the possible prediction of the dehydration degree. A total number of 113 children diagnosed with gastroenteritis were retrospectively enrolled and divided based on viral etiology into group 1 (34 children with unknown viral etiology), group 2 (60 children with rotavirus) and group 3 (19 children with adenovirus). Results: The highest mean Vesikari and modified Vesikari scores were found in group 2 (p < 0.01; p = 0.01). A significant increase in liver enzymes was also identified in patients infected with rotavirus. The highest mean diarrhea, vomiting duration and body temperature were found in group 3 (p < 0.01; p < 0.01; p = 0.02), as well as the highest mean inflammatory markers, such as C-reactive protein (CRP; p = 0.01) and the erythrocyte sedimentation rate (p < 0.01). Significant linear associations were found between pH, bicarbonate level, base excess and the Vesikari scores, whereas urea, CRP and aspartate aminotransferase levels were associated with both severity scores. ROC curve analysis revealed a significant correlation between the Vesikari scores and dehydration degree (p < 0.01), with numeric cut-off values of 11.5 being proposed for the differentiation between mild and moderate gastroenteritis and 13.5 for the distinction between moderate and severe gastroenteritis. Conclusions: Both severity scores are useful in clinical settings, but more studies enrolling populations with various enteral infections could provide more insight into their etiology-based performance and reflection of paraclinical changes.

Prevalence and genetic characterization of viral gastroenteritis in hospitalized children aged <5 years in Yunnan Province, China, 2020-2022

Background

Rotavirus (RV), norovirus (NoV), human enteric adenovirus (HAdV), human astrovirus (HAstV), and sapovirus (SaV) are important viral causes of acute gastroenteritis (AGE) in children. However, limited information is available regarding AGE in Yunnan, Southwest China.

Methods

To investigate the prevalence of group A rotavirus (RVA), norovirus genogroups I (GI) and II (GII), and HAdV, HAstV, and SaV in children aged <5 years hospitalized with AGE between 2020 and 2022.

Results

Stool samples were collected from 612 children hospitalized with AGE. A total of 266 of the 612 children presented with AGE (43.46%; 266/612). RVA was detected in 28.76% (176 of 612) of the children. Rotavirus G9P[8] was the most frequent genotype in 2020 and 2021. In 2022, G8P[8] became the dominant genotype combination circulating in Yunnan Province. The norovirus positivity rate was present in 11.93% (73/612) of the 612 samples. Of the 45 GII successfully sequenced samples, GII.4 was the dominant genotype, accounting for 51.11% (23 of 45), followed by GII.3 [P12] (28.89%; 13 of 45). The positivity rates for SaV, HAstV, and HAdV were 2.94% (18/612), 3.43% (21/612), and 4.74% (29/612), respectively. HAdV-F41 was the predominant genotype and non-enteric HAdV-C2 and HAdV-A12 were also observed in Yunnan. Male children had a higher incidence of AGE than female children upon infection with RV, NoV, and HAdV. The highest incidence of AGE was observed among children aged between 12 and 23 months (62.50%; 120/192), followed by children aged between 24 and 35 months (52.44%; 43/82). The incidence rate of the infection peaked (78.62%; 125/159) in the first 3 months of the year, followed by the next 3 months (66.67%; 70/105).

Conclusions

RV and NoV remained the most important agents causing AGE. RV G8P[8] became the dominant circulating genotype instead of G9P[8] in Yunnan in 2022. The authors suggest that monitoring should be strengthened to prevent outbreaks caused by RV G8P[8]. New vaccines, such as the RV G8P[8] genotype, should be considered.

Impact of rotavirus vaccination in Malawi from 2012 to 2022 compared to model predictions

Rotarix® vaccine was introduced into the Malawi national immunization program in October 2012. We analyzed data on children <5 years old hospitalized with acute gastroenteritis from January 2012 to June 2022, and compared to pre-vaccination data from 1997 to 2009. We estimated vaccine coverage before, during, and after the COVID-19 pandemic using data from rotavirus-negative children. We compared the observed weekly number of rotavirus-associated gastroenteritis (RVGE) cases by age to predictions from a previously developed mathematical model to estimate overall vaccine effectiveness. The number of RVGE and rotavirus-negative acute gastroenteritis cases declined substantially following vaccine introduction. Vaccine coverage among rotavirus-negative controls was >90% with two doses by July 2014, and declined to a low of ~80% in October 2020 before returning to pre-pandemic levels by July 2021. Our models captured the post-vaccination trends in RVGE incidence. Comparing observed RVGE cases to the model-predicted incidence without vaccination, overall effectiveness was estimated to be modest at 36.0% (95% prediction interval: 33.6%, 39.9%), peaking in 2014, and was highest in infants (52.5%; 95% prediction interval: 50.1%, 54.9%). Our mathematical models provide a validated platform for assessing strategies to improve rotavirus vaccine impact in low-income settings.

Impact of rotavirus vaccination in Malawi from 2012 to 2022 compared to model predictions before, during, and after the COVID-19 pandemic

Background

Rotarix® rotavirus vaccine was introduced into the Malawi national immunization program in October 2012. We used a previously developed mathematical models to estimate overall vaccine effectiveness over a 10-year period following rotavirus vaccine introduction.

Methods

We analyzed data on children <5 years old hospitalized with acute gastroenteritis in Blantyre, Malawi from January 2012 to June 2022, compared to pre-vaccination data. We estimated vaccine coverage before, during, and after the COVID-19 pandemic using data from rotavirus-negative children. We compared model predictions for the weekly number of rotavirus-associated gastroenteritis (RVGE) cases to the observed number by age to validate model predictions and estimate overall vaccine effectiveness.

Results

The number of RVGE and rotavirus-negative acute gastroenteritis cases declined substantially following vaccine introduction. Vaccine coverage among rotavirus-negative controls was >90% with two doses by July 2014, and declined to a low of ~80% in October 2020, before returning to pre-pandemic levels by July 2021. Our models captured the post-vaccination trends in RVGE incidence, with 5.4% to 19.4% of observed weekly RVGE cases falling outside of the 95% prediction intervals. Comparing observed RVGE cases to the model-predicted incidence without vaccination, overall vaccine effectiveness was estimated to be 36.0% (95% prediction interval: 33.6%, 39.9%) peaking in 2014 and was highest in infants (52.5%; 95% prediction interval: 50.1%, 54.9%).

Conclusions

Overall effectiveness of rotavirus vaccination in Malawi is modest despite high vaccine coverage and has plateaued since 2016. Our mathematical models provide a validated platform for assessing strategies to improve rotavirus vaccine impact.

Impact of rotavirus vaccine introduction in Abidjan, Côte d'Ivoire

Côte d'Ivoire introduced rotavirus vaccine in March 2017. Rotavirus surveillance is conducted at Centre Hospitalier Universitaire de Yopougon in Abidjan, the capital city. Children <5 years of age are enrolled in rotavirus surveillance if admitted to the hospital with acute gastroenteritis. We used sentinel surveillance data from 2014 through mid-2019 to compare trends in rotavirus pediatric gastroenteritis hospitalizations before and after rotavirus vaccine introduction. We used Poisson regression to analyze changes in rotavirus prevalence, adjusting for calendar month and accounting for total monthly admissions; January 2014 - December 2016 was considered "pre-vaccine," and January 2017 - June 2019 was considered "post-vaccine." Age distribution and severity were compared between periods using the Mann-Whitney U test. Rotavirus-positive admissions declined 51% (95% CI: 28%-67%), from 31.5% pre-vaccine to 14.9% afterward. The median age of rotavirus-positive children increased from 7 months (interquartile range [IQR]: 5-11) in the pre-vaccine period to 11 months (IQR: 7-18, p = .005) in the post-vaccine period. The median severity score decreased from 11 to 9 (p = .008) among all children, and from 12 pre- to 10.5 post-vaccine (p = .35) among rotavirus-positive children. Our findings suggest that rotavirus vaccine introduction contributed to reduced rotavirus hospitalization in Abidjan and possibly more broadly.

Leveraging Beneficial Off-Target Effects of Live-Attenuated Rotavirus Vaccines

Following the introduction of live-attenuated rotavirus vaccines in many countries, a notable reduction in deaths and hospitalisations associated with diarrhoea in children <5 years of age has been reported. There is growing evidence to suggest that live-attenuated vaccines also provide protection against other infections beyond the vaccine-targeted pathogens. These so called off-target effects of vaccination have been associated with the tuberculosis vaccine Bacille Calmette Guérin (BCG), measles, oral polio and recently salmonella vaccines, and are thought to be mediated by modified innate and possibly adaptive immunity. Indeed, rotavirus vaccines have been reported to provide greater than expected reductions in acute gastroenteritis caused by other enteropathogens, that have mostly been attributed to herd protection and prior underestimation of rotavirus disease. Whether rotavirus vaccines also alter the immune system to reduce non targeted gastrointestinal infections has not been studied directly. Here we review the current understanding of the mechanisms underlying off-target effects of vaccines and propose a mechanism by which the live-attenuated neonatal rotavirus vaccine, RV3-BB, could promote protection beyond the targeted pathogen. Finally, we consider how vaccine developers may leverage these properties to improve health outcomes in children, particularly those in low-income countries where disease burden and mortality is disproportionately high relative to developed countries.