Precision Matters: The Critical Role of Site of Injection Accuracy in In Ovo Vaccination

“Assuming you’re using the correct vaccine and the vaccine remains viable, the next most important factor is where that vaccine is placed within the embryo,” he explained.

Successful in ovo vaccination aims to deliver the vaccine into either:

• Embryonic tissue (subcutaneous or intramuscular).
• The amniotic sac surrounding the embryo.

These locations allow the embryo to properly absorb the vaccine and generate an effective immune response before hatch.

However, if the vaccine is accidentally deposited into other compartments-such as the air cell or the allantoic cavity-the immune response may be greatly reduced or completely absent.

For this reason, maintaining precise site of injection is essential for maximizing vaccine efficacy and ensuring consistent flock protection.

Comparing In Ovo Vaccination Devices

During his presentation at the World Poultry Congress, Dr. Deines presented data comparing the site of injection accuracy of several commercially available in ovo vaccination systems.

Zoetis, through its Embrex technology, pioneered in ovo vaccination more than three decades ago. As additional technologies have entered the market, the company sought to evaluate differences in injection accuracy among the leading systems.

The results demonstrated substantial variation.

According to Dr. Deines, the Embrex in ovo system achieved injection accuracy approaching 100% when targeting the embryo or the amniotic sac.

By comparison, two other major commercial systems achieved approximately 87% injection accuracy.

The remaining injections were often deposited into less desirable locations, including:

• The air cell.
• The embryo’s internal body cavity.
• Other non-target compartments.

These misplaced injections may reduce vaccine effectiveness while also increasing the potential for embryo trauma.

In addition, the competing systems failed to deliver vaccine to approximately 7-8% of viable embryos, leaving a portion of chicks unprotected before hatch.

“Our findings reinforce just how important site of injection accuracy is for successful vaccination,” Dr. Deines noted.

Improving Egg Identification Accuracy

Beyond injection placement, the study also evaluated how accurately vaccination systems distinguish viable embryos from nonviable eggs before vaccination.

Dr. Deines explained that some competing technologies mistakenly classify a small percentage of live embryos as nonviable, removing them from the hatching process.

The study found that competing systems removed approximately 0.6-0.75% of live embryos, resulting in an immediate reduction in hatchability.

By contrast, the Embrex system successfully retained viable embryos while efficiently removing nonviable eggs, including clears.

According to Dr. Deines, the system consistently removes more than 99.5% of clear eggs, helping improve hatchery efficiency without unnecessarily sacrificing live embryos.

Technology Supported by Service

Equipment performance depends on more than engineering alone.

Dr. Deines explained that Zoetis supports hatcheries through a comprehensive service model designed to maintain the long-term accuracy of Embrex in ovo technology.

This support begins with equipment designed specifically for hatchery environments, where machines must perform consistently despite demanding operating conditions and multiple users.

The company’s leasing model includes:

• Equipment installation.
• Operator training.
• Preventive maintenance.
• Ongoing technical service.

Together, these services help ensure that vaccination equipment continues operating according to its original design specifications throughout its lifespan.

The Value of Process Evaluations

Even with advanced equipment, maintaining vaccination quality requires continuous monitoring.

Dr. Deines described Zoetis’ process evaluations as comprehensive operational audits that help hatcheries verify that every step of the vaccination process follows established best practices.

These evaluations examine multiple aspects of hatchery operations, including:

• Site of injection accuracy.
• Equipment performance.
• Sanitation procedures.
• Vaccine handling.
• Overall vaccination workflow.

The objective is not only to identify potential problems but also to provide practical recommendations that help hatcheries maximize the value of their vaccination programs.

Process evaluations can reveal opportunities to improve efficiency, reduce biological risks and prevent issues such as bacterial contamination during vaccine preparation or application.

By regularly reviewing operational procedures, hatcheries can maintain consistent vaccination performance while protecting chick health and optimizing production outcomes.

Precision Throughout the Vaccination Process

Throughout the interview, Dr. Deines reinforced that successful in ovo vaccination depends on precision at every stage-from correctly identifying viable embryos to delivering vaccines into the optimal anatomical location.

While advances in vaccination technology have significantly improved hatchery efficiency, consistent results ultimately depend on combining accurate equipment, proper maintenance, operator training and routine process evaluations.

As hatcheries continue seeking ways to maximize bird health and production performance, ensuring accurate site of injection remains one of the most effective strategies for delivering reliable immune protection before chicks even hatch.