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Home » H5N1 flu virus (bird flu) vaccine development and availability

H5N1 flu virus (bird flu) vaccine development and availability

On the heels of a widening outbreak of bird flu in the USA, caused by the H5N1 influenza virus, I wanted to find information about the possibility of a vaccine for H5N1. Of course, the story about a vaccine for this outbreak is complex, and I thought it would be useful for my readers to get the most recent up-to-date information.

This article will review what we know about the H5N1 virus and the potential of vaccines.

brown hen near white egg on nest H5N1 vaccine
Photo by Alison Burrell on

All about bird flu

Avian influenza, or what everyone is now calling “bird flu,” is a subtype of type A influenza, designated as A(H5N1). Without getting into all the details of the naming system, the designation is based on antigens common to this influenza subtype. Another avian influenza is designated as A(H7N9), but the current outbreak appears to be the H5N1 subtype.

As the name implies, these viruses usually affect birds but they can occasionally pass from birds to humans, cattle, pigs, and other animals. The H5N1 subtype arose in Asia a few years ago and has spread across the world. It is highly pathogenic (meaning it can cause disease in humans) and has passed to humans several times.

Infected birds shed the bird flu virus through their saliva, mucous, and feces. Human infections with bird flu viruses can happen when the virus gets into a person’s eyes, nose, or mouth, or is inhaled. This can happen when the virus is in the air (in droplets or possibly dust) and a person breathes it in, or possibly when a person touches something that has the virus on it and then touches their mouth, eyes, or nose. Human infections with bird flu viruses have occurred most often after unprotected contact with infected birds or surfaces contaminated with bird flu viruses. However, some infections have been identified where direct contact with infected birds or their environment was not known to have occurred.

There are numerous cases where bird flu has been transmitted between humans, but most infections of humans are from constant contact with infected birds. Human infection with avian influenza A virus poses pandemic potential, so CDC and other public health agencies investigate every case to assess whether human-to-human transmission might have occurred. Detailed public health investigations can help determine whether person-to-person spread of an avian influenza A virus occurred.

The signs and symptoms of bird flu infections in humans can range from nothing to severe. The infections are similar to other flu infections including fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue, and shortness of breath.

person holding laboratory flask H5N1 vaccine
Photo by Chokniti Khongchum on

H5N1 vaccine research and development

Until data show that there is human-to-human spread of the H5N1 virus, there is probably no need for widespread vaccination. The CDC is closely monitoring the situation, so, as of today, no one is recommending mass vaccination.

Because H5N1 has been around for a few years, the CDC has stockpiles of vaccines for the H5N1 and H7N9 subtypes. And if either avian influenza mutates, the CDC has a method to develop new vaccines quickly. The Administration for Strategic Preparedness and Response manages the National Pre-Pandemic Influenza Vaccine Stockpile (NPIVS) program which allows the CDC to rapidly respond to new influenza stains as they evolve. NPIVS works with vaccine manufacturers to develop and test updated vaccines that match new strains of influenza viruses with pandemic potential. NPIVS also supports manufacturing capacity to allow for large-scale vaccine production if a pandemic is predicted from a particular flu strain.

There are currently three H5N1 vaccines that have been approved for the following manufacturers: Sanofi, GSK, and CSL Seqirus. Each of the vaccines is in the NPIVS system in preparation for a potential H5N1 pandemic. GSK has contracts with the USA, Canada, European Union, World Health Organization, and other governments to quickly provide the H5N1 vaccine in case of a pandemic.

However, this stockpile is small and would be targeted to healthcare frontline workers while larger stocks would be produced by the vaccine manufacturers. It would not be practical to build large stocks now because we don’t know what strain of the H5N1 virus would predominate during a pandemic. If that happens, the CDC and governmental public health agencies across the world would isolate the strain and then have the vaccine manufacturers ramp up production.

Sanofi, GSK, and CLS Seqiris are very competent flu vaccine manufacturers and could ramp up production rather quickly after a strain is identified.

There is a potential roadblock to this — most flu vaccines are manufactured using chicken eggs. If the bird flu continues to grow, it might harm chicken egg production which would lead to hampering the production of the H5N1 vaccines. Thus, even now, research is ongoing to produce flu vaccines that do not require chicken eggs.


As I’ve mentioned elsewhere, right now we do not have any cases of human-to-human transmission of the H5N1 virus. That means a pandemic is not likely at this time.

However, a small mutation to the H5N1 virus could cause it to become more infectious and pathogenic. And since we don’t have an immunity to the virus, it could spread widely and quickly. That’s why the CDC and other public health agencies across the world are monitoring the situation in the USA.

Michael Simpson

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