Innovations in poultry vaccination have led to significant improvements in farm performance, as evidenced by reduced morbidity, reduced mortality, increased production rates and improved animal welfare.

• Vector vaccines: These use attenuated or genetically modified viruses that carry a gene from another pathogen to induce the immune response, without the need to use the original microorganism. This has improved the safety and efficacy of vaccines.
• Recombinant vaccines: these use proteins or genes from the pathogen to stimulate the immune response and are specific.
• Subunit vaccines: These use specific fragments, called antigenic subunits, from either viruses or bacteria that are recognized by the immune system. They are very safe and economical to develop.
• DNA/RNA vaccines: Specific fragments of the genetic material (DNA or RNA) of the pathogen can be used to stimulate the immune response in poultry. These vaccines are stable, safe and can be rapidly produced.
• Nanostructures in vaccines: The incorporation of nanostructures into vaccines allows for the controlled release of antigens, improving the efficacy of the immune response and the duration of protection.

In ovo vaccination

Embryonic chickens have a functioning immune system by 16 to 18 days incubation. Vaccination of embryonic chicks in ovo is a highly effective method of vaccinating large numbers of birds in a very short time. Automatic egg injection machines have been widely adopted. Injection through the eggshell is performed at 18.5 days when eggs are routinely transferred to hatching trays to avoid turning in the setter compartment of the incubator.

In ovo vaccination requires specialized equipment, great accuracy, and a very high degree of hygiene because once opened to the environment by a needle puncture, eggs are susceptible to bacterial or fungal invasion. With appropriate hygienic precautions, the method is highly satisfactory. It is predominantly used for Marek’s disease vaccines containing the CVI 988/Rispens strain of virus. It may also be used for control of infectious bursal disease in addition to fowl pox, and avian influenza.