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Avian flu vaccine may save California condors

I almost always focus on vaccines for humans, though I will occasionally discuss vaccines for pets, but this will be a new one for me — a vaccine to save the iconic California condors.

The California condor is a vulture that is the largest land bird in North America. The species went extinct in the wild in 1987, when the last remaining wild California condors were captured to use for breeding. Eventually, the birds were reintroduced to northern Arizona and southern Utah (including the Grand Canyon area and Zion National Park), the coastal mountains of California, and northern Baja California in Mexico. The birds were killed off by agricultural chemicals (DDT), poaching, lead poisoning, and habitat destruction.

Today, there are over 200 California condors flying in the wild (with a similar number still in captivity). That’s not exactly a robust population, so the species remains critically endangered.

Unfortunately, a form of avian flu has killed some of the California condors, so a vaccine has been developed that may prevent the disease in these majestic birds. I’m going to review this innovative use of a new vaccine to save an endangered species.

california condor on tree
Photo by Juan Felipe Ramírez on

Avian flu and California condors

The California condors are being attacked by highly pathogenic avian influenza (HPAI), often called bird flu, which is caused by two forms of influenza A (H5N1 and H7N9) virus that attack many different animals, mostly birds. As of May 12, 2023, twenty-one condors have died related to HPAI infections in 2023. This is a significant hit to the California condor population.

The HPAI epidemic has not only caused significant harm to the extant California condor populations but it has also caused outbreaks in poultry farms over the past two years. Moreover, avian influenza could infect humans, although it is rare, and it also does not spread far when it does jump to humans. But if the virus mutates to a form that easily transmits from human to human, it could lead to a serious epidemic or pandemic since most of us lack antibodies to avian influenza.

California condors and the HPAI vaccine

The United States Department of Agriculture’s Agricultural Research Service (APHIS) announced they approved the emergency use of a highly pathogenic avian influenza (HPAI) vaccine candidate to prevent additional deaths of California condors. The emergency use authorization is only for use in California condors.

Since this HPAI vaccine has not previously been tested against this strain of the virus in the California condors, the first step in the vaccination program is a pilot safety study in North American black vultures, a similar species, to investigate if there are any adverse effects before giving the vaccine to the endangered condors.

This trial is funded by the U.S. Fish and Wildlife Service and will be carried out with the surrogate vultures in North Carolina beginning in May 2023. The authorized vaccine is a killed, inactivated product conditionally licensed by the Animal and Plant Inspection Service‘s (APHIS) Center for Veterinary Biologics in 2016.

As of late September 2023, the US Fish and Wildlife Service has not made a decision as to when or even if they will vaccinate the condors against HPAI as they wait for further information from the preliminary trial in North Carolina.


I had a chance to see two California condors in Pinnacles National Park in northern California a few years ago. They were simply wonderful to watch float on thermals high above me. I was truly lucky.

This avian influenza outbreak threatens the species again. We are not getting any breaks in trying to preserve the species. However, the US Fish and Wildlife Service is doing its best to protect the California condor from avian influenza and other risks like humans shooting and killing them.

Michael Simpson

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