^a This is an example of a typical vaccination program. Individual programs are highly variable and reflect local conditions, disease prevalence, severity of challenge, and individual preferences.

^b Most USA commercial broiler hatcheries use an in ovo vaccination system for Marek’s disease at 17–19 days of embryonation. Infectious bursal disease vaccine (mild strain) may be combined with Marek’s disease vaccines. Vectored vaccines in which Marek's and fowlpox vaccines have been safely modified to carry immunizing antigens for laryngotracheitis, Newcastle disease, or infectious bursal disease are also commonly used in ovo or day-old chicks. Connecticut strain is often combined with Massachusetts. Bronchitis vaccine is usually combined with Newcastle. Other bronchitis strains such as Arkansas 99 and Florida 88 are included in some areas. Vaccinations at 14–21 days are optional. A single drinking water application for Newcastle disease/bronchitis is also common.