The U.S. Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) is expected this week by August 21 to issue a request for proposal (RFP) to vaccine manufacturing companies to have avian influenza vaccine produced to protect U.S. poultry from future outbreaks of highly pathogenic H5N2 avian influenza (HPAI).

The doses of vaccine would be kept on hand in the National Veterinary Stockpile for use only at a point necessary to eradicate the HPAI virus, the agency has told U.S. poultry industry representatives who have participated in weekly conference calls with APHIS officials.

The National Turkey Federation and U.S. turkey producers have sought federal authorization of the use of vaccine for eradication of HPAI as a tool for officials to make available for at-risk farms, particularly for the hardest-hit areas of the upper Midwest.

Many U.S. broiler industry members have advocated a cautious approach to any use of avian influenza vaccination for fear of disrupting U.S. poultry exports for world markets.

At a recent meeting in Des Moines, APHIS researchers shared data from trials of an avian flu vaccine with U.S. poultry industry members that showed the vaccine effective in chickens.

Dr. John Glisson of the U.S. Poultry & Egg Association told WATT PoultryUSA, “The data shared by AHIS in the meeting in Des Moines showed the vaccine was highly effective in preventing the clinical signs of the disease in chickens. The vaccine very significantly reduced the shedding of the virus in infected birds.”

Vaccine trials in turkeys had not been completed at the time of the Des Moines meeting.

APHIS officials are said to be emphasizing that the vaccine would be used only as a tool in the HPAI eradication program being conducted in the U.S. and only at a point necessary to eradicate the virus.

Glisson explained the rationale behind the agency’s approach: “Because avian influenza vaccines don’t prevent infection and don’t stop shedding entirely, vaccination by itself does not control spread of the disease. Vaccination, however, can be a useful tool as part of a disease eradication program.”

“There is no influenza vaccine that prevents avian influenza infection,” he noted, “and there’s no vaccine that prevents infected birds from shedding the virus.”

The Southeast Poultry Research Laboratory’s Dr. David Swayne recently explained the way a vaccine’s effectiveness is measured: “Vaccine protection or efficacy is measured primarily by two means in vaccinated poultry: prevention of clinical disease and mortality, and a reduction in virus shedding, which reflects the growth of the challenge virus and release of the virus in body secretions (oral secretions and feces). Decreased virus shedding is important in reducing environmental contamination, and thus reducing virus transmission and infection.”