Evolution of DS-1-like G8P[8] rotavirus A strains from Vietnamese children with acute gastroenteritis (2014-21): Adaptation and loss of animal rotavirus-derived genes during human-to-human spread.

Animal rotaviruses A (RVAs) are considered the source of emerging, novel RVA strains that have the potential to cause global spread in humans. A case in point was the emergence of G8 bovine RVA consisting of the P[8] VP4 gene and the DS-1-like backbone genes that appeared to have jumped into humans recently. However, it was not well documented what evolutionary changes occurred on the animal RVA-derived genes during circulation in humans. Rotavirus surveillance in Vietnam found that DS-1-like G8P[8] strains emerged in 2014, circulated in two prevalent waves, and disappeared in 2021. This surveillance provided us with a unique opportunity to investigate the whole process of evolutionary changes, which occurred in an animal RVA that had jumped the host species barrier. Of the 843 G8P[8] samples collected from children with acute diarrhoea in Vietnam between 2014 and 2021, fifty-eight strains were selected based on their distinctive electropherotypes of the genomic RNA identified using polyacrylamide gel electrophoresis. Whole-genome sequence analysis of those fifty-eight strains showed that the strains dominant during the first wave of prevalence (2014-17) carried animal RVA-derived VP1, NSP2, and NSP4 genes. However, the strains from the second wave of prevalence (2018-21) lost these genes, which were replaced with cognate human RVA-derived genes, thus creating strain with G8P[8] on a fully DS-1-like human RVA gene backbone. The G8 VP7 and P[8] VP4 genes underwent some point mutations but the phylogenetic lineages to which they belonged remained unchanged. We, therefore, propose a hypothesis regarding the tendency for the animal RVA-derived genes to be expelled from the backbone genes of the progeny strains after crossing the host species barrier. This study underlines the importance of long-term surveillance of circulating wild-type strains in order to better understand the adaptation process and the fate of newly emerging, animal-derived RVA among the human population. Further studies are warranted to disclose the molecular mechanisms by which spillover animal RVAs become readily transmissible among humans, and the roles played by the expulsion of animal-derived genes and herd immunity formed in the local population.

The cost of delivering COVID-19 vaccines in Vietnam.

BACKGROUND: The COVID-19 pandemic affected hundreds of millions of people and lives, and vaccination was the safest and most effective strategy to prevent and mitigate the burden of this disease. The implementation of COVID-19 vaccination in Vietnam in 2021 was unprecedentedly challenging in scale and complexity, yet economic evidence on the cost of delivery vaccines thought the program was lacking. METHODS: This retrospective costing study utilized a bottom-up, ingredient-based approach to estimate the cost of delivering COVID-19 vaccines in Vietnam in 2021, from a payer perspective. The study included 38 study sites across all administrative and implementation level, including three geographic areas and two delivery strategies, in two provinces, Hanoi and Dak Lak. The study findings were complemented with qualitative interviews with health staff and stakeholders. RESULTS: The economic cost to deliver one COVID-19 vaccine dose was $1.73, mostly comprised of opportunity costs ($1.14 per dose) which were driven by labor costs ($1.12 per dose). The delivery cost in urban areas was the highest ($2.02), followed by peri-urban areas ($1.45) and remote areas ($1.37). Delivery costs were higher at temporary sites ($1.78) when compared to facility-based delivery ($1.63). Comparing low-volume and high-volume periods showed that the delivery cost decreased significantly as volume increased, from $5.24 per dose to $1.65 per dose. CONCLUSIONS: The study estimates the cost of delivering COVID-19 vaccines in Vietnam in 2021. Enabling factors and challenges during the implementation of the program were explored. Study limitations may lead to underestimation of results and reduce generalizability.

Pertussis vaccination during pregnancy in Vietnam: Results of a randomized controlled trial Pertussis vaccination during pregnancy.

A pertussis vaccination during pregnancy has recently been adopted in several countries to indirectly protect young infants. This study assessed the effect of adding a pertussis component to the tetanus vaccination, in the pregnancy immunization program in Vietnam. A randomized controlled trial was performed. Pregnant women received either a Tdap (tetanus, diphtheria acellular pertussis) vaccine or a tetanus only vaccine between 19 and 35 weeks' gestational age. Immunoglobulin G (IgG) against tetanus (TT), diphtheria (DT), pertussis toxin (PT), filamentous hemaglutinin (FHA) and pertactin (Prn) were measured using commercial ELISA tests, at baseline, 1 month after maternal vaccination, at delivery, and in infants from cord blood and before and after the primary series (EPI: month 2-3-4) of a pertussis containing vaccine. Significantly higher geometric mean concentrations (GMC) were observed for all 3 measured pertussis antigens in the offspring of the Tdap group, up to 2 months of age. One month after completion of the primary infant vaccination schedule, anti-Prn GMC, but not anti-PT and anti-FHA GMCs, was significantly (p=0.006) higher in the control group. Maternal antibodies induced by vaccination during pregnancy close the susceptibility gap for pertussis in young infants. Limited interference with the infant vaccine responses was observed. Whether this interference effect disappears with the administration of a fourth vaccine dose is further studied.

Coverage of the expanded program on immunization in Vietnam: Results from 2 cluster surveys and routine reports.

UNLABELLED: The Expanded Program on Immunization (EPI) in Vietnam began in 1981 and reached a 87% national coverage rate in 1987. To investigate the vaccination coverage and trends in time of the EPI in Vietnam, 2 vaccine coverage cluster surveys have been conducted in 2003 and 2009. Information on EPI-vaccine coverage in children (aged 0-23 months - 7 y of age), in women of childbearing age and in pregnant women, was collected through '30 cluster surveys' in 2003 and 2009 (according to the World Health Organization (WHO) methodology) and through routine annual EPI coverage reports for the period 2001-2008. By comparing both cluster survey studies with each other, as well as with routinely collected data, we aim to improve future evaluation of the vaccination coverage in Vietnam and deduce recommendations for the immunization program. According to both methods, the national targets were reached for most of the vaccines: over 90% of children are fully immunized by 1 y of age, 80% Tetanus Toxoid 2 Plus (TT2+) coverage is reached for pregnant women, and 90% TT2+ for childbearing aged women. The cluster surveys identified higher coverage rates compared to the routinely reported data in some provinces regarding the percentage of fully immunized children by the age of 1 year, and confirmed a low coverage rate for hepatitis B birth dose vaccination in all surveyed sites. CONCLUSION: Both methods of coverage assessment suggest that national targets are reached, for most but not all vaccines and not in all regions. Managing stock pile issues, addressing safety issues and tailoring policy for remote areas, are important elements to maintain and further improve these coverage figures.