What I mean by that, is that sometimes a person will not generate a protective immune response to a particular vaccine on a given day… the whole point of vaccination.
Now that person might respond (and have responded) just fine to other vaccines. Or they might respond to that exact same vaccine just fine on another day. Or they might get that same vaccine several times, and never generate a protective response.
We do not know why this happens, thus we cannot predict who will or will not respond well. And then we dont know who responded well until the non-responders get sick. Thus you, me, we could be ‘non-responders’ to measles, and we wont know it until we get sick because some jerk decided not to vaccinate their kids, and then let their measles infested children attend a concert we all attend.
Happily, not responding to a vaccine is infrequent. If everyone was vaccinated, the rates of ‘not responding’ are still low enough that they, and everyone else, should be protected via herd immunity.
BUT, if we understood why this phenomenon happens, we could figure out ways around it to make sure everyone who gets a vaccine reaps its benefits, and we know it.
We do know the bare bones of what is going on–
Some of it has to do with environment– maybe the non-responders allergies were really acting up that day, or maybe they thought they were over a recent cold more than they actually were, and that interfered with the vaccines efficacy.
And some if it might have to do with our genetics. Somehow. Somewhere. We dont really know outside of obvious things like MHC type :-/
We just gained a bit more insight into why some people do not respond well to the measles vaccine:
CD46 measles receptor polymorphisms influence receptor protein expression and primary measles vaccine responses in naive Australian children.
Measles needs a protein on the surface of your cells in order to successfully mediate infection: CD46
There are some differences between individuals CD46 gene, thus differences in CD46 protein shape and function.
To stop measles from infecting a cell, you need to stop the interaction between measles and CD46. Usually that is mediated by neutralizing antibodies– antibodies stick to the virus and prevent its virusy arms from grabbing onto the cell it wants to infect.
But if not all CD46 proteins are equal, then preventing the measles-CD46 interaction might be an easy… or a difficult… task. Maybe stopping the interaction is difficult because of high affinity between a particular CD46 variant and measles. Maybe it is more difficult because a particular CD46 variant is transcribed or translated or processed faster, thus there is a lot more of it available on the cell surface for measles to find. We dont know.
These scientists looked at kids who had just gotten the measles vaccine, and compared the CD46 genes of the responders and the non-responders. The children who had mutations at the right spot, in a particular flavor, seemed to respond better than others. But if a child had a mutation at the right spot, but not a mutation of the right flavor, they didnt respond as well.
Now, there were not many children in this group, and the participants were white (limiting the genetic diversity sampled), but it is pretty neat to have this kind of information! So, all of you folks out there with a ‘GG’ at location rs2724384, stay away from people with measles! You might not be protected!!
Which highlights the fact that this research has “unclear clinical relevance at this stage”. Those words are straight from the author. Its not me being a Debbie Downer this time!
Lets say the experimental group was HUGE and there was a clear-cut connection between your genetics and how you respond to a vaccine. What are we supposed to do with that information? There is nothing we can do about it.
All we can do is keep investigating not only the differences, but the clear how/why of the differences, so we might be able to figure out how to turn a non-responder into a responder. So this isnt super useful information YET… but it will be one day!