A review of rotavirus vaccine use in Asia and the Pacific regions: challenges and future prospects

Progress in research and development of preventive vaccines for children in China

The infant and child stage is an important stage for the continuation and development of human society. The initial years of life have a lasting impact on a child's future. Children under the age of 5 have an immature immune system, especially infants and young children under 6 months of age. At this stage, the population has a low immunity to pathogen infections, making them vulnerable to bacteria and viruses. Vaccination can enhance the immunity of infants and children to specific diseases, reduce the transmission rate of infectious diseases, and promote the development of global public health. This article summarizes the current application status of Rotavirus (RV) vaccine, Hand-foot -mouth disease (HFMD) vaccine, and Pneumococcal Conjugate Vaccine (PCV) in China, as well as the research progress of clinical trial vaccine, laying a foundation for subsequent vaccine development.

Genetic diversity of G9, G3, G8 and G1 rotavirus group A strains circulating among children with acute gastroenteritis in Vietnam from 2016 to 2021

Rotavirus group A (RVA) is the most common cause of severe childhood diarrhea worldwide. The introduction of rotavirus vaccination programs has contributed to a reduction in hospitalizations and mortality caused by RVA. From 2016 to 2021, we conducted surveillance to monitor RVA prevalence and genotype distribution in Nam Dinh and Thua Thien Hue (TT Hue) provinces where a pilot Rotavin-M1 vaccine (Vietnam) implementation took place from 2017 to 2020. Out of 6626 stool samples, RVA was detected in 2164 (32.6%) by ELISA. RT-PCR using type-specific primers were used to determine the G and P genotypes of RVA-positive specimens. Whole genome sequences of a subset of 52 specimens randomly selected from 2016 to 2021 were mapped using next-generation sequencing. From 2016 to 2021, the G9, G3 and G8 strains dominated, with detected frequencies of 39%, 23%, and 19%, respectively; of which, the most common genotypes identified were G9P[8], G3P[8] and G8P[8]. G1 strains re-emerged in Nam Dinh and TT Hue (29.5% and 11.9%, respectively) from 2020 to 2021. G3 prevalence decreased from 74% to 20% in TT Hue and from 21% to 13% in Nam Dinh province between 2017 and 2021. The G3 strains consisted of 52% human typical G3 (hG3) and 47% equine-like G3 (eG3). Full genome analysis showed substantial diversity among the circulating G3 strains with different backgrounds relating to equine and feline viruses. G9 prevalence decreased sharply from 2016 to 2021 in both provinces. G8 strains peaked during 2019-2020 in Nam Dinh and TT Hue provinces (68% and 46%, respectively). Most G8 and G9 strains had no genetic differences over the surveillance period with very high nucleotide similarities of 99.2-99.9% and 99.1-99.7%, respectively. The G1 strains were not derived from the RVA vaccine. Changes in the genotype distribution and substantial diversity among circulating strains were detected throughout the surveillance period and differed between the two provinces. Determining vaccine effectiveness against circulating strains over time will be important to ensure that observed changes are due to natural secular variation and not from vaccine pressure.

Rotavirus in developing countries: molecular diversity, epidemiological insights, and strategies for effective vaccination

Rotavirus (RV) causes the loss of numerous children's lives worldwide each year, and this burden is particularly heavy in low- and lower-middle-income countries where access to healthcare is limited. RV epidemiology exhibits a diverse range of genotypes, which can vary in prevalence and impact across different regions. The human genotypes that are most commonly recognized are G1P[8], G2P[4], G3P[8], G4P[8], G8P[8], G9P[8], and G12P[8]. The diversity of rotavirus genotypes presents a challenge in understanding its global distribution and developing effective vaccines. Oral, live-attenuated rotavirus vaccines have undergone evaluation in various contexts, encompassing both low-income and high-income populations, demonstrating their safety and effectiveness. Rotavirus vaccines have been introduced and implemented in over 120 countries, offering an opportunity to assess their effectiveness in diverse settings. However, these vaccines were less effective in areas with more rotavirus-related deaths and lower economic status compared to wealthier regions with fewer rotavirus-related deaths. Despite their lower efficacy, rotavirus vaccines significantly decrease the occurrence of diarrheal diseases and related mortality. They also prove to be cost-effective in regions with a high burden of such diseases. Regularly evaluating the impact, influence, and cost-effectiveness of rotavirus vaccines, especially the newly approved ones for worldwide use, is essential for deciding if these vaccines should be introduced in countries. This is especially important in places with limited resources to determine if a switch to a different vaccine is necessary. Future research in rotavirus epidemiology should focus on a comprehensive understanding of genotype diversity and its implications for vaccine effectiveness. It is crucial to monitor shifts in genotype prevalence and their association with disease severity, especially in high-risk populations. Policymakers should invest in robust surveillance systems to monitor rotavirus genotypes. This data can guide vaccine development and public health interventions. International collaboration and data sharing are vital to understand genotype diversity on a global scale and facilitate the development of more effective vaccines.

Access to DTP-Based Combination Vaccines in Asia-Pacific Countries between 2019 and 2022

The Asia-Pacific countries are highly diverse in health and economic conditions that may impact vaccine access and uptake. Our study aimed to characterize patterns of health access to DTP-based combination vaccines in 10 countries from 2019 to 2022 using the IQVIA-MIDAS database. The availability, affordability, and accessibility were compared across countries by national health and economic performance indicators using Spearman's rank correlation coefficient. Our findings showed that the three aspects of access to DTP-based vaccines varied substantially in the Asia-Pacific region, with higher levels in countries with better health and economic performance. Affected by the COVID-19 pandemic, vaccine accessibility fluctuates significantly in lower-income countries, with DTP coverage rates falling by more than 14% in the Philippines and Indonesia between 2019 and 2021. For availability and affordability, Singapore and Malaysia from high-income groups were largely affected, which may be related to health expenditure as a percentage of gross domestic product (Coefficient = 0.39, p = 0.03). Our study indicates that greater attention needs to be paid to national health expenditure and routine immunization services to improve vaccine disparities and increase the robustness and resilience of the vaccine supply chain during public health emergencies.

No increased risk of intussusception after pentavalent rotavirus vaccination in China: a retrospective birth cohort using electronic health records of Ningbo city

Some post-licensure studies have shown a potential increased risk of intussusception following vaccination with rotavirus vaccines. This is the first study that aimed to assess the incidence and risk of intussusception within 90 days after vaccination with RotaTeq in Chinese infants. A population-based birth cohort from 27th November 2018 to 30th June 2021 included all newborns in Ningbo city. The records of intussusception were identified through the ICD-10 code K56.1 or Chinese keywords "Chang Tao" from all hospital discharge records. Each episode was confirmed in line with the Brighton criteria, and only Brighton level 1 cases were included. The association of RotaTeq vaccination and intussusception was evaluated using the Poisson regression. A total of 108,405 eligible subjects from birth cohort were eligible, with 52.30% males. Among them, 26, 847 (24.77%) infants received at least one dose of RotaTeq, and 95.52% of them were fully vaccinated, with 76, 934 doses in total. After adjudication, none of the cases occurred post first, or second dose, the cumulative number of cases that occurred 1-7, 1-14, 1-21, 1-42, and 1-90 days post third dose was 0, 1, 1, 3, and 7, respectively. Adjusting for age, sex, birth year, birth season and location, the incidence rate ratio of intussusception after RotaTeq vaccination was 0.90 (90% two-sided CI: 0.46, 1.75). Increasing age and male gender were associated with higher risk of intussusception. In summary, no increased risk of IS was observed following 3 months of RotaTeq vaccination in this study.

Immunogenicity and safety of a new hexavalent rotavirus vaccine in Chinese infants: A randomized, double-blind, placebo-controlled phase 2 clinical trial

Rotavirus remains a major cause of diarrhea among 5-y-old children, and vaccination is currently the most effective and economical measure. We conducted a randomized, double-blind, placebo-controlled phase II clinical trial designed to determine the dosage, immunogenicity, and safety profile of a novel hexavalent rotavirus vaccine. In total, 480 eligible healthy infants, who were 6-12 weeks of age at the time of randomization were randomly allocated (1:1:1) to receive 105.5 focus-forming unit (FFU) or 106.5FFU of vaccine or placebo on a 0, 28 and 56-d schedule. Blood samples were collected 28 d after the third dose to assess rotavirus immunoglobulin A (IgA) antibody levels. Adverse events (AEs) up to 28 d after each dose and serious adverse events (SAEs) up to 6 months after the third dose were recorded as safety measurements. The anti-rotavirus IgA seroconversion rate of the vaccine groups reached more than 70.00%, ranging from 74.63% to 76.87%. The postdose 3 (PD3) geometric mean concentrations (GMCs) of anti-rotavirus IgA among vaccine recipients ranged from 76.97 U/ml to 84.46 U/ml. At least one solicited AE was recorded in 114 infants (71.25%) in the high-dose vaccine group, 106 infants (66.25%) in the low-dose vaccine group and 104 infants (65.00%) in the placebo group. The most frequently solicited AE was fever. The novel oral hexavalent rotavirus vaccine was safe and immunogenic in infants support the conclusion to advance the candidate vaccine for phase 3 efficacy trials.

A Clinical Nursing Care Study on the Prevalence of Rotavirus Infection and Acute Diarrhea in Vaccinated Chinese Pediatric Population from 2019-2022

Purpose

To investigate the prevalence of rotavirus infection and acute diarrhea after immunization and further assess the quality of nursing care provided by the nurses to such patients.

Methods

A total of 432 children aged 3–36 months with acute diarrhea between February 2019 and March 2022 were enrolled, and rotavirus testing was performed within 24 h using a rotavirus enzyme immunoassay kit. Clinical characteristics were evaluated, and regression analysis was performed.

Results

Eighty vaccinated children (18.5%) were confirmed to have rotavirus infection out of 432 children. The prevalence of rotavirus positivity was the highest at 20–28 months (22 cases, 24.44%) and 11–19 months age group (27 cases, 22.50%). There is a significant association between rotavirus infection and hygiene score (p = 0.009). Based on the association with quality of nursing care, rotavirus infection was association with “appropriate care” (p = 0.001).

Conclusion

Rotavirus infection was strongly associated with poor hygiene score which may be due to the hygienic nature of the mother and her family. Nursing care assessments revealed a huge gap between nurses and the guardians, which reflects the behavior of Chinese nurses. Thus, an intervention is required by the policymakers for implementing effective strategies of quality nursing for the improvement of the pediatric patients with rotavirus gastroenteritis.

Epidemiology and genetic diversity of group A rotavirus in pediatric patients with acute gastroenteritis in Thailand, 2018-2019

Group A rotaviruses (RVAs) are the major viruses that cause acute gastroenteritis in young children worldwide. The objective of this study was to investigate the prevalence and genotype diversity of RVAs circulating in children with acute gastroenteritis in Thailand in 2018-2019. A total of 1170 stool specimens were obtained from children admitted to hospitals with diarrhea and screened for RVAs by nested RT-PCR. The RVA genotypes were determined by multiplex-PCR or nucleotide sequencing and phylogenetic analysis. Out of 1170 stool specimens, 209 (17.9%) were positive for RVAs. The RVA G9P[8] genotype (24.4%) was the most dominant genotype, followed by G3P[8] (22.9%), G8P[8] (22.0%), G1P[8] (16.7%), G2P[4] (6.7%), G1P[6] (2.3%), G1P[4] (1.0%), G3P[4] (1.0%), G9P[4] (1.0%), mixed-infections of G1P[4] + G1P[8] (1.0%), and GXP[8] (0.5%). Moreover, an uncommon RVA G3P[10] genotype (0.5%), bearing bat-like VP7 and VP4 genes, was detected. This study reveals the prevalence and genetic diversity of RVA genotypes in children with acute gastroenteritis in Thailand. The knowledge obtained from this study is helpful for understanding the epidemiology of rotavirus in Thailand. The emergence of uncommon RVA strain G3P[10] provides an evidence for interspecies transmission of human and animal rotaviruses.