The Flu Vaccine: Another Animal Research Victory

It’s that time of year again where the threat of the flu hangs in the air and people scramble to their local pharmacies to get their annual flu shot. Did you know this life-saving vaccine was created thanks to animal research?

In 1918 and 1919, the Spanish Influenza caused the death of at least 50 million people, and over 500 million people – about a third of the world’s population at that time – were infected with the Spanish influenza virus. Since there was no vaccine for the flu, people were forced to limit public gatherings and even turned to complete isolation or quarantine to prevent any further spreading of the flu. In 1935, Sir Frank Macfarlane Burnet was the first person to isolate the influenza virus. Three years later, scientists Jonas Salk, MD, and Thomas Francis Jr., MD, developed the first flu vaccine with the help of fertilized chicken eggs. Since then, another type of flu vaccine has been developed using mammalian cells instead of fertilized chicken eggs.

Animal models have proven to be ideal in influenza research studies because they make it possible for scientists to study how the influenza virus infects the body and how it is transmitted from one person to the next, thus enabling researchers to evaluate various interventions and therapies. One of the first animal models to be used in research for the flu vaccine was the ferret. They are an ideal candidate for flu vaccine studies because they are infected by the flu in much the same way as humans. They experience a fever, runny nose, and even sneezing! Ferrets have also proven useful in helping researchers understand how the flu is transferred – person to ferret, ferret to person, and ferret to ferret. In addition, ferrets have helped in studying the pandemic potential of various flu strains such as the avian and swine flu strains. The ferret is truly a valuable animal model for the flu!

Mice and guinea pigs are also important animal models for understanding and treating the influenza virus. While these two animals do not exhibit the same symptoms of the flu as humans – and ferrets! – do, they present other advantages. Mouse models are small and easy to handle, making them useful in pre- clinical studies of influenza therapies. More recently, researchers have identified immune response mechanisms to influenza that are similar in mice and humans, opening the door to new, more effective treatments for the flu. Guinea pigs are smaller than ferrets, which means a greater number of guinea pigs can be placed in environmentally controlled spaces. As a result, guinea pigs have proven useful in influenza transmission studies.

Today, the flu vaccine is able to reduce the risk of contracting the virus by 40 to 60%. Each flu season, the different flu strains vary in their strength, and they mutate, which means that it is extremely difficult to determine which flu strains the seasonal flu vaccine should target. This is happening in the current flu season. The World Health Organization announced this year’s flu shot may not be as effective as it could be, as it is missing two specific flu strains that have recently struck in the Southern Hemisphere.

Though this year’s flu shot may be a mismatch, the Centers for Disease Control and Prevention still recommend that everyone six months and older become vaccinated because the flu shot still provides some coverage, attenuates symptoms, and reduces the risk of transmission to other people.

Thanks once again to animal models (especially the ferret!), for their help in the discovery of yet another lifesaving vaccine.

 

By Nelia Dashiell