**1. Introduction**

Disease control and prevention in industrial poultry production relies mainly on biosecurity and vaccination [1, 2]. Biosecurity focuses on decreasing the possibility of agent entry into poultry barns, or reducing the environmental agent load by cleaning, disinfection, prevention of contact with wildlife, and entry/exit control of personnel and equipment, thus decreasing the likelihood or severity of the infection and/ or delaying the age of infection [1–4]. In contrast, vaccination focuses on decreasing the susceptibility to pathogens likely to cause economic losses [1, 5] and/or preventing colonization by food-borne diseases (e.g., *Salmonella enterica*) [6]. Commercial vaccines are designed to target major and constant threats for the industry, common to several poultry markets worldwide and, as such, demand production of a high number of dosages across the world that justify the costly process of research, development, registration, marketing, and testing of each master seed and final product serial release. Because these problems are constant for the industry and homologous challenges to classic vaccines are prevalent in the field, these products are expected to stay relevant for decades, thus covering their expenses and generating revenues for vaccine-producing companies for a long time. Examples can be found in different vaccines, including but not limited to Marek's disease (MDV-Rispens, HVT-FC126; SB1), Avian encephalomyelitis (AE), Fowlpox (FP), Newcastle disease (NDV), Avian

Reovirus (ARV) (cluster 1.1), Infectious bronchitis (e.g., serotypes Massachusetts, Connecticut), Chicken Anemia Virus (CAV), all of them with long product life cycles that are still relevant today, after decades of use since research, development, and registration [7–9]. As of March 2022, in the US, there are more than 1000 active licenses for veterinary vaccine products [10]. However, if the challenge agent is shown to be antigenically different (antigenic variants) from the classic strains present in standard licensed vaccines, the immunity elicited by these licensed vaccines might be insufficient to prevent the economical consequences of the challenge. Thus, control of disease might require "emergency," "custom-made," "complex-specific," or "farm-specific" autogenous vaccines made with isolates obtained from affected flocks [11–14].
