Impact of rotavirus vaccination on diarrheal disease burden of children in South America.

INTRODUCTION: Rotavirus is a leading cause of severe diarrheal disease and death in children under five years of age worldwide. Vaccination is one of the most important public health interventions to reduce this significant burden. AREAS COVERED: This literature review examined vaccination coverage, hospitalization rate, mortality, genotypic distribution, immunogenicity, cost-effectiveness, and risk versus benefit of rotavirus vaccination in children in South America. Nine out of twelve countries in South America currently include a rotavirus vaccine in their national immunization program with coverage rates in 2022 above 90%. EXPERT OPINION: Introduction of the rotavirus vaccination has led to a marked reduction in hospitalizations and deaths from diarrheal diseases in children under 5 years, particularly infants under 1 year, in several South American countries. In Brazil, hospitalizations decreased by 59% and deaths by 21% (30-38% in infants). In Peru, hospitalizations in infants fell by 46% and deaths by 37% (56% in infants). Overall, data suggest that rotavirus vaccination has reduced rotavirus deaths by 15-50% in various South American countries. There is some evidence that immunity wanes after the age of 1-year old. Ongoing surveillance of vaccine coverage and changes in morbidity and mortality is important to maximize protection against this disease.

Defect resonance frequency of spherical pore within isotropic elastic solid.

Ultrasound based porosity imaging in metals, composite or additive manufactured structures pose a challenge due to various absorbing media. This paper addresses this problem by developing a defect resonance frequency equation that will be used for individual porosity imaging. An analytical model is developed for closed spherical shell supported on elastic foundation based on the six mode shell theory. The defect resonance frequency is calculated from the breathing mode, corresponding to maximum out-of-plane displacement, when supporting stiffness tending towards rigid condition. Thereafter, steady state and explicit dynamic analysis are carried out for a mild steel specimen with single and multiple pores to detect the defect resonance frequency along with defect mode. Further, the defect resonance frequency is validated with experiment involving a mild steel specimen with single spherical pore. The numerical and experimental results are good agreement with the results obtained from defect resonance frequency equation. This defect resonance frequency equation can be used for high resolution imaging of porosities.

Resonant activation of different intermodulation frequencies using dual excitations.

In this paper, an analytical framework is presented to understand the generation of different intermodulation frequencies under dual excitation which is also verified with experiments. One single periodic frequency (SPF) excitation along with one variable frequency excitation, varying from local defect resonance (LDR) frequency and its superharmonics to subharmonic, are used. The flexural wave propagation in an orthotropic composite plate containing a delamination is analytically derived considering quadratic nonlinearity. Both analytical and experimental results are presented for glass fibre reinforced plastic (GFRP) plates with single and double delaminations. Two different types of intermodulation peaks are observed, that is local defect resonance intermodulation (LDRI) and single periodic frequency intermodulation (SPFI), out of which SPFI is found to be generated only during superharmonics and subharmonic excitation. At LDR frequency excitation, only its higher harmonics are found and no SPFI peaks are observed. The acoustic nonlinearity parameters are found increase with order of harmonics and delamination diameter.