US government is testing avian flu vaccines for birds, but ending the historic outbreak isn't that simple

CNN

Some experts call it a 'new era of bird flu' in the United States.

Since January 2022 the country has been fighting the largest outbreak of highly pathogenic bird flu in wildlife. The virus poses a serious threat to backyard and commercial flocks. It has also been found in hundreds of animals, including pet cats.

According to the US Centers for Disease Control and Prevention (CDC), the risk for humans is very low. There has only been one human case in the US, and nine worldwide, mostly among those who work with bird. According to the CDC, vaccines are being tested that may be used in order to protect humans if and when the virus becomes more dangerous.

Separately the US Department of Agriculture and the US National Poultry Research Center, as well as labs in a few American universities, have been testing vaccine candidates for use on birds.

USDA's Agriculture Research Service began testing four vaccine candidates in April. The USDA expects to release initial data this month on a single dose vaccine. In June, results from a two-dose challenge study should be available. This involves exposing animals to the virus in order to test the effectiveness of the vaccine.

The USDA will then work with the manufacturers to determine if it is feasible to use the vaccines.

Zoetis announced on April 5 that it was developing a vaccine to combat the current virus strains. It is estimated that it will take the company about a full year to reach the US distribution stage.

Other countries have already made vaccines available, such as China, Egypt. Indonesia, Italy, Mexico, and Vietnam. Some nations also vaccinate their commercial flocks.

In the United States however, some poultry experts have not been ready to use vaccines, even if they were available. They are focusing on eliminating the virus.

Eradication of disease and vaccination

The CDC reports that as of April 26th, nearly 58.8 millions poultry had been infected with avian influenza since January 2022. At least 6,737 wild bird species have been infected with the virus, but that number is likely much higher. In 47 states, there have been outbreaks of poultry.

According to the USDA, despite this being the largest outbreak in history, biosecurity measures have greatly reduced the number cases in the commercial poultry sector. In early 2022 there were 51 cases of commercial poultry being infected. In March 2023 there were seven.

USDA states that the reduction of cases is due to the close collaboration between its Animal and Plant Health Inspection Service and state and industrial partners.

Rodrigo Gallardo is a professor of poultry medicine at the University of California Davis and an expert in avian virus.

"One is vaccination." He said that the second method is eradication.

Gallardo stated that the United States is currently pursuing the second approach.

Farmers will immediately put down birds if they detect even one case.

Gallardo explained that 'the virus is always replicating and amplifying as long as the birds are still alive. The only way to stop the replication and limit the spread of the disease is through depopulation.

Tom Super, senior vice president of communications for the National Chicken Council (the national trade association for US broiler poultry industry), said in an email sent to CNN that, although the organization supports ongoing discussions regarding a vaccination programme, it 'currently supports the eradication policies of APHIS' and believes that this is currently the best way to eliminate [bird flu] from the U.S.

US Poultry and Egg Association stated that it is a 'certainly topic of discussion', but does not have a stance on the implementation of a vaccination program.

Complications from vaccination

Gallardo says that a vaccination program can have several complications. Although vaccinated birds are protected from this disease, the virus can still spread to unprotected animals.

Gallardo explained that if vaccination is not performed correctly, it can lead to an amplification.

It's also difficult to detect disease in vaccinated poultry. Birds that have been vaccinated may not always show symptoms of illness, making it difficult to tell which birds should be kept apart. The tests are also unable to distinguish between antibodies produced by vaccination and those from an infection.

Gallardo stated that 'if you can't diagnose it or eradicate it, then it could spread much more than if it was diagnosed and eradicated.

The virus never completely disappears in countries that choose the vaccine route.

If you do not update your vaccine to match the changes in the virus you will not be able to protect birds completely. Gallardo explained that partial protection would mean more birds spreading the virus.

According to the USDA, a vaccine against highly pathogenic bird flu has never been used in the US. The USDA created a new vaccine in response to an outbreak that occurred between 2014 and 2015. However, the strain involved was different, so the vaccine would not work with the most recent version of the virus.

Dr. Yuko Sato, associate professor at the College of Veterinary Medicine of Iowa State University, says that logistics are a challenge when it comes to a vaccine of this kind.

Sato explained, 'You need to ensure that the new vaccination will protect you against the current virus. You also have to hope that this virus doesn't change or mutate so that it will continue to remain protective.

The vaccine isn't a magic bullet. It will not prevent the infection of birds. To have a strategy for the country's exit, you must ensure that, even if the vaccine is successful, the virus can be eradicated. We will never be able to eradicate the virus in the United States if we don't take action.

Bird businesses may be threatened by vaccines

Another issue: birds are big business in the US.

With 294,000 farms, the US has the world's largest poultry industry. According to IbisWorld, the market for chicken and turkey production is expected to reach $57.8 Billion by 2023.

According to the National Chicken Council, bird flu has caused serious business losses in the US. However, it could be worse if the country vaccinates its poultry.

The National Chicken Council opposes the use of [bird flu] vaccines for many reasons, the main one being the trade. The US and most other countries do not consider countries that have vaccinated against [bird flu] as being free from the disease. This is because vaccines may mask the presence. Super wrote that they don't accept exports coming from countries who vaccinate.

The US broiler chicken industry is the second biggest exporter of poultry in the world. The US exports approximately 18% of all chicken meat produced, worth more than $5 billion per year.

Super stated that if we started vaccinating against [bird flu] here in the U.S. the broiler industries would lose their ability to export, which would have a significant effect on the industry. It will also cost the U.S. economic billions every year.

Scientists would have to immunize wildlife, which is almost impossible.

Super stated that of the birds affected by this outbreak, 76% were commercial egg-laying chickens, 17% were turkeys and only 5% were broilers – the meat-producing chickens. Ducks, backyard chickens, and game birds are the rest of those affected.

He said that the U.S. chicken sector, which has the least need for a vaccine, would be the one most at risk if it used a vaccination.