How Vaccine Development Progressed in the Last 20 Years
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James Merson, chief scientific officer at the Vaccines Research Unit at Pfizer, discusses the progress of vaccine development over the last 20 years.

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Topic – From Polio to Hepatitis B James Merson: Vaccines have a variety of guises, so some of the early vaccines were known as attenuated vaccines. That is the infectious organism had been changed such it could still replicate in the human body, but not cause disease. This is what happened with the first vaccine identified by Jenner using cowpox as a means of preventing smallpox. Cowpox had sufficient similarity to smallpox. It could elicit, induce an immune response which was protective against smallpox, so that was a whole live virus, which was used to prevent smallpox. Later on, people were using what is known as killed vaccines, so influenza is a good example where influenza is grown up in eggs or tissue culture. It’s killed and then administered as a killed virus to the individual via hypodermic needle and those proteins are seen as being foreign by the immune system. They’re an infectious disease. They don’t belong to the body and, therefore, an immune response is mounted. More recently, people have been able to identify specific proteins from an infectious organism. A nice example is the hepatitis B vaccine where the surface protein isolated from the virus via genetic engineering and just that single protein is grown up, purified, and then used as a vaccine and just the immune response to that single protein is able to prevent the individual from becoming infected by the virus. So there are numbers of ways that one can generate a vaccine. Question – Where are we today? James Merson: Tremendous amount of change over the last 20 years. Part of this has been enabled by the molecular biology revolution coming out of the ‘70s and ‘80s, which allowed us to clone and express proteins from various infectious diseases, particularly viruses, bacteria, fungi, and being to work with those proteins has enabled us to get a better understanding as to how those infectious organisms infect individuals, how they evade the immune system. Specifically it’s allowed us to find Achilles’ heels for the various bugs, whether it be for antibiotics targeting various proteins and bacteria to prevent them from replicating or antiviral drugs where we can inhibit a viral protein to prevent the virus from replicating in a human cell. Genetics have been very important for us to understand how to make better vaccines against some of these infectious organisms. Studying these bugs at a very detailed level and their interaction with the immune system helps us understand how we can perhaps help the immune system do a better job at preventing infection. So generating vaccines that don’t utilize the whole infectious organism, just using parts of it and by generating what we would call a neutralizing immune response, whether it be antibodies which bind specifically to proteins on the bug and effectively take it out of circulation and prevent the person from being infected. The science around infectious diseases has been really quite key to our understanding and give us really key insights into the immune system. Based on our increased understanding of the immune system over the last 20 odd years has enabled us to discern how we can use the immune system to manage disease in a way that people probably hadn’t thought about only a few years ago. Question – Who are your public health heroes? James Merson: Being so interested in vaccines and seeing how much potential they hold for us I think we have to see Jenner who effectively invented vaccination as being a tremendous steward and inventor in the area. He probably is my number one public health hero, but then we have to go to people who like Salk and Sabin who invented the polio vaccines and you can go on and on. But I think it’s probably because the vaccines have had such a major impact in improving public health throughout the whole world that one has to look to the vaccinologist as being public health heroes.