Transcript:

Viruses: Polio vs InfluenzaWhy do we need to get a new flu vaccine every year when we only need one vaccination for polio? I'm Jim Metzner and this is the Pulse of the Planet.McDonald: We need a new vaccine every year because the virus is changing constantly. And if the virus is able to change very slightly, our immune system no longer can recognize it.Virologist Sarah McDonaldMcDonald: What scientists do is about a year out from flu season they start looking at the viruses and seeing "What does it look like this year?" They take samples from all over the world, and they make predictions about what they think it's going to look like six months from now. When you're getting the flu vaccine, essentially what you're getting is a formulation that was based on an educated guess from the scientists of what was circulating about six months ago. There's this conundrum of why do we get a polio virus vaccine when we're a child and that protects us against all the polio virus strains that seem to be circulating around the world, and it protects us for life. But flu, we need to get a vaccine every year. Polio has the same capacity to change as influenza does. So they're both changing, but what's different is the way our immune systems recognize the viruses and where the changes are occurring. And the places, or sites, where the changes occur vary for different viruses.McDonald: Unfortunately for influenza, our immune systems identify the virus at the exact sites that the virus is changing. Whereas, for polio our immune systems recognize the virus at sites that don't change very frequently. So, for those viruses like the flu which change in ways that our immune system can recognize, we need a new vaccine every year. For viruses like polio, where any changes are not recognized by the immune system, one vaccine seems to do the job. Pulse of the Planet is made possible in part by Virginia Tech, inventing the future with a hands on approach to education and research.