You may have heard some of the news in the past week or two about a newly developed malaria vaccine. Malaria is tricky for vaccine development because of the complexity of the virus life cycle. The parasite changes the way it looks to the immune system as it goes through developmental stages, so even if you have a great vaccine for one stage, it doesn’t help with the other stages. Trying to figure out the best way to target the vaccine is also difficult. Based on what we know of the natural history – that people develop some immunity, but not complete immunity – it may not be practical to expect that a vaccine could generate enough of an immune response to completely squelch the parasite. But you could reduce the parasite load in a given individual, so that transmission to mosquitoes does not occur as easily. This would also reduce symptoms and severe complications. The vaccine has been an ideal, but for decades vaccine success was always something that was another 10 years down the road.
Currently, the Swiss company Mymetics has announced the success of their malaria vaccine Phase Ib clinical trials in Tanzania. The vaccine they developed was a DNA-based vaccine targeted toward 2 separate parasite stages. It was tested among 40 kids over a 12-month period, and the trial was considered successful because of the high rates of seroconversion (70-80%) among the study subjects. Note that Phase 1 trials (see below) focus on safety, not effectiveness. The company is currently preparing for the next study phase.
Clinical trials are the only form of “experimental” epidemiology. The general phases are:
- Phase I: Researchers test a new drug or treatment in a small group of people for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.
- Phase II: The drug or treatment is given to a larger group of people to see if it is effective and to further evaluate its safety.
- Phase III: The drug or treatment is given to large groups of people to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug or treatment to be used safely.
- Phase IV: Studies are done after the drug or treatment has been marketed to gather information on the drug’s effect in various populations and any side effects associated with long-term use.
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