The U.S. Department of Agriculture isn’t planning on widespread vaccination of poultry and layer flocks, but its considering how it might do so in the event of an outbreak of highly pathogenic avian influenza (HPAI).

During the Watt Global Media webinar, Vaccination as Part of an Avian Flu Eradication Plan, Dr. Lee Ann Thomas, director of the Avian, Swine & Aquatic Animal Health Center at the USDA’s Animal and Plant Health Inspection Service (APHIS), discussed what factors the agency would consider when making the decision of whether or not to approve use of the stockpiled avian influenza vaccines in the U.S.

Thomas said any decision to vaccinate will follow a science-based strategy focused on suppressing and eradicating the disease. With an established eradication plan and maintenance of enhanced biosecurity in mind, the agency would conduct a controlled vaccination of at-risk flocks, then monitor all vaccinated and at-risk birds before carrying out a repopulation plan.

Before making the decision to vaccinate, APHIS would consider the probability of containing the spread of the virus; the proximity of high-value genetic breeder birds to the outbreak; poultry density in the area that may be vaccinated; the possible increased risk of introduction of HPAI into uncontaminated flocks and the presence of HPAI transmitting waterfowl.

As for which birds would get vaccinated first, Thomas said APHIS would consider how effective a vaccine is in each species, which commodities would be impacted by an HPAI outbreak, how close farms are to one another, the outbreak pattern, and the type of flock.

Thomas stressed that no decision has been made to vaccinate birds in the U.S. The decision, she said, will ultimately lie with the agency’s administrator, Kevin Shea. If the decision is made, it would be supervised by incident command in the area, who would be charged with developing the plan for vaccination, reporting vaccine usage, permitting movements and monitoring all activities.

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Logistically, Thomas said, immunizing millions of birds would be challenging. The efforts must be coordinated to ensure that national biosecurity is not compromised and that vaccination teams do not become unwitting transmitters of the virus. There would also need to be continuous monitoring of the immunized population to ensure there is no vaccine break.

The decision will not be made lightly, as widespread vaccination of the nation’s flocks could stymie foreign market’s appetite for U.S. poultry and eggs. Thomas said the December 2014 to June 2015 outbreak of HPAI led to the depopulation of 50 million birds and impacted the U.S.’s relationship with 17 trading partners, including China, Russia and South Korea.

While no decision has been made to immunize, USDA is already stockpiling millions of doses of vaccines that showed promise in preventing the spread the HPAI. Dr. David Suarez, the research leader for exotic and emerging avian viral disease research at the USDA’s Agricultural Research Service (ARS), said the U.S.’s options are limited because only licensed vaccines can be deployed by the USDA. In order to both incentivize the private sector to develop newer, more effective vaccines, and stock up for the event of a mass immunization, the USDA is building a stockpile of millions of doses of vaccine.

The two avian influenza vaccines purchased by USDA APHIS for the stockpile had different costs. The vaccines are being added to the stockpile at costs to USDA of $0.06 and $0.125 per dose by Ceva Animal Health and Harrisvaccines, respectively. 

While there is some skepticism about the efficacy of vaccines in stopping HPAI outbreaks, Dr. Leslie David Sims, a consultant for Asia Pacific Veterinary Information Service, Australia, said empirical research gathered through decades of fighting HPAI outbreaks in Southeast Asia proves that vaccines, when properly administered, can be effective in halting the spread of the virus on specific farms and in wider geographic areas.