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Why malaria vaccine is a world first
In Summary
- Dr Cohen is the co-inventor and one of the original patent holders of RTS,S. As vice president of R&D for vaccines for emerging diseases and HIV at GlaxoSmithKline Biologicals, he manages early development of vaccines against some of the world’s leading infectious diseases, including HIV, TB and malaria.
What is the significance of a successful malaria vaccine?
Scientifically, the significance is enormous. We have vaccines against bacterial and viral agents but no vaccine has ever been made against a human parasite. This is thus a world first.
Tell us about the RTS,S vaccine development.
I started this project in 1987, and for a number of years it was tedious work: Making the vaccine, manufacturing it, testing it in animals, and then finally in 1992 testing it for the first time in human subjects.
Then, only a few people were protected out of the eight that we vaccinated. The results were encouraging, but not satisfactory.
But in 1996, when we tested a new formulation of the vaccine, six out of the seven volunteers who had been vaccinated were completely protected. I think that was a “Eureka” moment.
What about the risks of the vaccine especially since you’ve added the Hepatitis B vaccine protein, a vaccine that has been associated with autoimmune diseases?
There is a quite rigorous way of assessing the safety of a vaccine with the phases 1, 2 and 3 clinical trials. Even beyond phase 3, after the vaccine is adopted, we still do a post-marketing study to check for any side-effects or risks.
We now have more than 8,000 doses of the vaccine that have been administered to 3,000 children in Africa. We have followed the safety rigorously, and we haven’t seen any cause for alarm and certainly no indication of autoimmunity.
It is also not an easy thing to evaluate autoimmunity, because it may develop 20 years after whatever its initial cause was.
How many shots does a child need for protection?
In the phase 2 trials, conducted in Africa over the past nine years, we found that we need three doses administered one month apart. That fits very well with the usual EPI programme and its visit schedules.
The vaccine is targeting children who are 6-14 weeks old and the second group is from 5-17 months. Isn’t there a risk that vaccinating such young children with so many vaccines could overwhelm their fragile, still developing immune systems?
A child in Africa or elsewhere is constantly subjected to a variety of external immuno-stimulants. So giving them a bit of protein from a microbe will not overload their immune system. However, there is a logistical problem that comes with the increasing number of new vaccines that need to be injected in the EPI schedule.
You are hoping to enrol 16,000 children for phase 3. Will you get scientifically significant data from such a sample size?
