G.H. Hudson1, K. Saravana Kumar2, Simmi Tomar3 and Surya Pratap Dhakare4
Introduction
Diseases in poultry production are one of the most important stressors in poultry operations, which considerably affect the profitability of the industry. Vaccination, on the other hand is a important operation in poultry production that enhances the health status of the birds, thereby protecting them from diseases or decreasing their severity. Conventionally, vaccines are given through drinking water or spray, which suffers from vaccine delivery failure and reduced vaccine efficiency. Vaccine injections, on the other hand, are labor-intensive and stressful, requiring individual birds to be handled. The in ovo vaccination technology was first described in 1982 for vaccination against Marek’s Disease. In 1992, Embrex BioDevices introduced the first commercial in ovo vaccination system. Currently, these machines have the capacity to inject over 70,000 eggs per hour. Over 90% of hatcheries in the United States have adopted this technique, with the global adoption rate reaching 32%. It has proven beneficial in preventing a number of bacterial, viral, and parasitic diseases, including Newcastle Disease, Marek’s Disease, Infectious Laryngotracheitis, Infectious Bronchitis, Infectious Bursal Disease, Avian Influenza, Turkey Rhinotracheitis, Mycoplasmosis, and coccidiosis. It provides early protection for chicks, reducing the need for post-hatch injections and ensuring that the birds are protected from diseases as soon as they hatch.
How it Works
Usual in ovo vaccine technology is applied between 17-19 days of egg incubation, where the embryos are sufficiently developed to absorb vaccines without significantly affecting hatching rates or chick quality. It involves piercing a hole in the top of the blunt end of the eggshell, then puncturing the egg membrane with an inoculated needle, injecting the vaccine slightly beneath the membranes at the bottom of the air cell. The exact location may vary depending on the embryo’s position, which can differ due to individual variation. For effective vaccination, the embryo should be in a hatching position with the yolk sac absorbed. However, puncturing the membranes can injure the embryo, potentially affecting hatchability and health. To avoid this, automated systems like the electromagnetic needle-free in ovo injection system have been developed for precise inoculation, reducing embryo injury and infection risks. Vaccines are typically injected into extra-embryonic sacs, especially the amniotic sac, or in some cases, the embryo’s breast, neck, or shoulder. The usual dose of vaccination is 50-100 microliters per egg. After vaccination, the embryo absorbs the vaccine through surrounding fluids, stimulating immune responses in the lymphoid tissues. Additionally, the vaccine may be absorbed through the respiratory tract or cloacal cavity.
Vaccination Sites

The chicken embryonated egg consists of five main compartments, each of which can serve as a potential site for vaccination, depending on the vaccine and the stage of egg development. The air cell, located at the broad end of the egg and filled with air, primarily functions in respiratory gas exchange and is generally not used for vaccine administration. The allantoic sac, which surrounds the embryo and contains waste products, is not a common site for vaccination. The amniotic sac, filled with amniotic fluid and surrounding the developing embryo, provides a protective environment for the embryo and is a common site for vaccination. This compartment allows for the absorption of vaccines into the embryo and is especially useful for vaccines requiring direct interaction with the developing chick. The embryo itself, which is the developing chick, can sometimes be inoculated directly with vaccines, although this requires careful handling to avoid harm to the embryo. Lastly, the yolk sac, which provides nutrients and maternal antibodies to the developing embryo, is another compartment where vaccines can be administered. This compartment is typically targeted for vaccines that rely on passive immunity or nutrient delivery, as it is closely connected to the embryo’s nourishment system. It was reported that the protection rates against MDV vaccines were 0%, 28.3%, 94.4%, and 93.9% following inoculation in the air cell, allantoic fluid, amniotic fluid, and the embryo’s body, respectively. Intracranial, intraorbital, or intraabdominal inoculations of embryos are regarded as unsatisfactory and ineffective methods and may cause embryonic death.
In ovo Vaccines
Marek’s Disease (MD) and Infectious Bursal Disease (IBD) vaccines are among the most commonly used in ovo vaccines. Boehringer Ingelheim introduced the first commercially available bivalent recombinant vaccine, Vaxxitek® HVT+IBD, which targets both MD and IBD. Later, they developed trivalent vaccines such as Vaxxitek® HVT+IBD+ND and Vaxxitek® HVT+IBD+ILT, offering protection against multiple diseases with a single dose. Currently, several companies provide commercial trivalent in ovo vaccines, including Merck’s INNOVAX-ND-IBD and INNOVAX-ND-ILT, as well as FARVET’s HVT-IBDV-LT. These bivalent and trivalent vaccines offer a convenient, cost-effective solution for preventing highly contagious and commercially harmful diseases affecting the global poultry industry. These developments demonstrate that creating polyvalent recombinant vaccines for in ovo immunization, along with optimizing vaccine composition and delivery methods, can enhance vaccination efficiency and reduce the stress-induced damage associated with repeated vaccinations in chickens.
Factors Influencing Vaccine Efficacy
The efficacy of in ovo vaccination is influenced by the following factors:
- Embryonic age of the egg.
- Site of injection.
- Vaccine preparation and handling.
- Hatchery hygiene and sanitation.
- Efficiency of in ovo vaccination machinery.
Automated In Ovo Vaccination Equipment
Automated vaccine delivery systems have made in ovo vaccination more accessible, even for smaller hatcheries. These systems are user-friendly and include brands like Embrex Inovoject, Innovatec, and Ceva, with varying capacities from 12,000 to 70,000 eggs. These systems feature optimized biosecurity and productivity with automatic needle cleaning and pre-vaccination egg removal. They are also compatible with all incubation trays and adjust the injection depth for each embryo.
Advantages of In Ovo Vaccination:
- Accurate and hygienic vaccine delivery.
- Reduced chick stress and handling on the farm.
- Lower labor involvement and reduced labor costs.
- Minimization of vaccination errors.
- Increased immune response to diseases.
- Faster transfer of chicks from hatchery to farm, as no vaccination is needed at hatch.
- Improved chick quality with fewer post-vaccination reactions.
Disadvantages of In Ovo Vaccination:
- High capital investment for in ovo vaccine delivery systems.
- Poor hatchery sanitation or equipment cleanliness can significantly reduce hatchability.
- Dependence on a reliable power supply, and the cost of servicing and replacing parts can be high.
Conclusion
In ovo vaccination technology presents a significant advancement in poultry farming, offering an efficient and less stressful alternative to traditional vaccination methods. In India, where poultry farming is a critical sector for both livelihood and economic growth, the adoption of in ovo vaccination could greatly enhance the health management of poultry flocks. The key advantages of in ovo vaccination, including accurate vaccine delivery, reduced chick stress, and minimized labor costs, align well with the growing demand for modern, cost-effective farming solutions in India. By preventing diseases like Marek’s Disease, Infectious Bursal Disease, Newcastle Disease, and others, this technology can reduce mortality rates, improve productivity, and enhance profitability for poultry farmers. The high initial capital investment for the vaccination equipment, the need for stringent hatchery hygiene, and reliance on a stable power supply are factors that may hinder widespread adoption. While there are some barriers to overcome, the benefits of in ovo vaccination could play a transformative role in enhancing poultry health management in India, contributing to a more sustainable and profitable poultry industry in the long run.