Commercial broiler flocks are routinely vaccinated against Marek's disease (MD), Newcastle disease (ND), infectious bronchitis (IB), infectious bursal disease (IBD/Gumboro disease), and coccidiosis, with program selection driven by regional circulating strains, production type, and route of administration.

For broilers, in ovo vaccination is the dominant delivery platform for MD. The herpes virus of turkey (HVT) vaccine was the first vaccine successfully administered in ovo, and the majority of commercial broilers in the United States transitioned from subcutaneous HVT administration to in ovo vaccination over a span of 20 years.Poultry Science Commercially, in ovo vaccines are now employed against MD, IBD, infectious laryngotracheitis (ILT), poxvirus, ND, avian influenza, and coccidiosis.Poultry Science

IBD vaccination programs for broilers include classical live vaccines, live HVT-IBD vector vaccines, and the Vaxxitek HVT+IBD recombinant product. Broilers vaccinated with Vaxxitek HVT+IBD show higher body weight at slaughter and lower feed conversion ratio and mortality compared to other IBD vaccine programs, though statistically significant differences were confirmed only for the European Poultry Efficiency Factor.Poultry Science Broilers vaccinated with an HVT-IBD vector vaccine against IB show increased average daily body weight gain of +1.13 g and lower feed conversion ratio of −0.05 compared to birds on classical live IBD vaccine programs.Poultry Science

For ND in broilers, the standard Israeli protocol — representative of intensive commercial programs — consists of a live vaccine by spray on the day of hatching, an inactivated vaccine by subcutaneous injection at 10–12 days of age, and a second live vaccine by aerosol at 17–21 days of age. At the peak of induced immunization at week 5, 87.5% of tested flocks achieved herd immunity, defined as ≥85% of birds with a hemagglutination inhibition titer ≥4.Avian Pathology Flocks without herd immunity carry an odds ratio of 3.7 for ND outbreak.Avian Pathology Classical genotype I and II vaccine strains exhibit reduced efficacy against genotype VII velogenic field strains due to antigenic divergence, and subgenotype VII.2 has been recovered from vaccinated commercial flocks in Pakistan, Israel, Mozambique, South Africa, Malaysia, Indonesia, and China.Poultry Science

IB vaccination most commonly combines Mass (H120 strain) and 793B (1/96 strain)-based vaccines. In Greece, this combination was the most widely implemented IBV program across commercial flocks, with a smaller number of farms using Mass alone or in combination with 4/91 or QX genotype-based vaccines.Poultry Science A vaccine program comprising GA08 (GI-27) and Mass-type (GI-1) strains significantly reduces transmission of the currently dominant DMV1639-type (GI-17) field strain in 4-week-old commercial broilers.Avian Pathology

ILT vaccination options include live-attenuated chicken embryo origin (CEO), live-attenuated tissue culture origin, and recombinant vectored vaccines, administered by aerosol spray, drinking water, eye drop, or subcutaneous injection depending on label.Journal of the… There are no chemical therapies for ILT; mass vaccination in the face of an outbreak may limit spread but can cause significant vaccine reactions and decreased performance.Journal of the… Live ILT vaccines carry a risk of reversion to virulence, and not all states or countries permit CEO vaccine use.Journal of the… Serology programs to evaluate ILT vaccination efficacy are difficult to interpret because humoral antibody titers to GaHV-1 do not reflect immune status; cell-mediated immune response is directly correlated to immune status.Journal of the…

Coccidiosis control in antibiotic-free (ABF) broiler programs relies on live non-attenuated coccidiosis vaccine administered by spray cabinet at the hatchery, replacing conventional shuttle programs of in-feed chemical anticoccidials from 0–20 days followed by polyether ionophores to slaughter.Poultry Science Vaccinated ABF flocks reach the oocyst excretion peak at 23.7 days versus 26.4 days in conventional shuttle flocks — a difference of 2.7 days — with no significant difference in peak oocyst count between programs.Poultry Science ABF vaccination programs show a decrease of 2.28 g in average daily gain and an increase of 0.08 in feed conversion ratio compared to conventional programs, with no significant differences in body weight at slaughter, livability, or condemnations.Poultry Science Vaccination also restores anticoccidial drug sensitivity: when a salinomycin program is followed by vaccination, salinomycin almost completely suppresses oocyst production from previously partially resistant Eimeria isolates.Poultry Science

For colibacillosis, vaccination of parent (breeder) flocks — not broilers directly — is the recommended control strategy. Broiler flocks from unvaccinated parents have a mean first-week mortality of 1.40% and mean total mortality of 4.33%.Preventive Vete… Broiler flocks from parents receiving both commercial and autogenous colibacillosis vaccines have the lowest mortality: mean first-week mortality of 0.91% and mean total mortality of 3.14%.Preventive Vete… Flocks from parents receiving commercial vaccine only fall between these groups.Preventive Vete… The autogenous vaccine must contain the avian pathogenic Escherichia coli (APEC) strain type causing local outbreaks, as strain-matching drives efficacy.Preventive Vete…

For layer and breeder flocks, vaccination programs extend to include pathogens affecting egg production and vertical transmission. Layers are immunized against pathogens causing decreases in egg production, salmonella, colibacillosis, and coccidiosis, in addition to the core broiler antigens.Poultry Science Mycoplasma gallisepticum (MG) vaccination in layers is administered as pullets prior to egg production initiation, as early as 9 weeks of age, via spray, eyedrop, wingweb, or intramuscular or subcutaneous routes depending on vaccine form.Poultry Science For inclusion body hepatitis (IBH), killed autogenous vaccines are used in the broiler breeder industry in the US to prevent vertical transmission, are typically bivalent containing serotypes FAdV8b and FAdV11, and birds receive 2 doses 2–4 weeks apart.Journal of the…

For avian influenza, hatchery vaccination of all day-old birds is the most efficient protocol for broiler, layer, and turkey sectors, with farm vaccination of all integrated farms being the efficient protocol for duck and guinea fowl sectors.Preventive Vete…

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