#### Introduction

The rise in antimicrobial resistance (AMR) threatens to cause a significant number of unnecessary deaths (O'Neill 2016; Naghavi et al. 2024) . To address this growing threat, policies have targeted antibiotic usage (ABU) reduction in the human, animal and environmental sectors (Chua et al. 2021). Indeed, AMR is a complex issue that must be addressed from a One Health perspective (McEwen and Collignon 2018). In this regard, the Tripartite Organization (World Health Organization, World Organization for Animal Health, and Food and Agriculture Organization) has established a Global Action Plan calling on member states to take action (OMS 2015). In this context, countries have developed and adopted their own National Action Plan (NAP) for the human and agricultural sectors. Vietnam was the first Southeast Asian country to adopt a national plan, followed by the Philippines in 2015 (Chua et al. 2021). It was approved in 2013, and followed in 2017 by the NAP for livestock and aquaculture (MARD 2017). The main objective was to 'tackle the human health risk related to ABR by better controlling the usage of antibiotics in livestock and aquaculture' (MARD 2017). A new NAP with similar objectives was adopted in 2021 (MARD 2021) based on five priorities: raising awareness of antibiotic resistance (ABR), promoting good farming practices and prudent ABU, monitoring ABU and ABR, strengthening international and cross-sectoral collaboration around ABR control, and lastly - the focus of our study - reviewing and enforcing regulations for the improved management of ABU. Several actions were taken to achieve the latter objective. The Law on Veterinary Medicine (National Assembly 2015) was amended with additional regulations to improve legislation governing ABU management. Antimicrobial growth promoters, which were widely used by Vietnamese farmers (Cuong et al. 2021; Kim et al. 2013) and contribute to antibiotic resistance (McEwen and Collignon 2018), were banned by the Animal Husbandry Law in 2018 (National Assembly 2018). The following decree (n°13/2020/ND-CP), was enacted to gradually cease the use of antibiotics in the feed for prophylaxis (Government of the Socialist Republic of Vietnam 2020). A roadmap of implementation from 2020 to 2025 was issued, starting with high-priority critically important antibiotics, followed by the other antibiotics on the WHO list of critical classes, and finally for all antibiotic classes (WHO 2019) with a complete ban planned for 2025. In 2020, a circular (n°122020TT-BNNPTNT) was issued to establish the prescription conditions for veterinary drugs, including antibiotics. The circular also included a roadmap of implementation, that started in 2020 for big-scale farms, 2022 for medium-scale farms, 2023 for small-scale farms, and will be implemented in 2025 for household farms (MARD 2020). These regulations also impact chicken production. The latter is a growing sector in Vietnam (Cesaro, Duteurtre, and Huong 2020) due to its ease of production, low investment requirements, and high consumer demand. Three types of chicken production systems are commonly defined: integrated farms, family commercial farms, and household farms, with small-scale farms being the most common (GSOV 2016; Bâtie et al. 2022). Interestingly, the different production systems were found to be strongly associated with the antibiotics and alternative feed additives value chain (Bâtie et al. 2022). Regulations are one of the most common solutions developed to attempt to reduce antibiotic use. However, policy implementation is influenced by both internal and external factors (Brugha2000)andneedstobe adaptedtothelocalcontexttobeeffective.Otherstudies in Vietnam have previously described the antibiotic value chain and policy development