Back in 2021, when we were still on constant alert for the unmasked roving about in public and didn’t know just how well the the SARSCoV2 mRNA vaccines would work, I made a mental note to read more about Measles Virus. My immediate question was whether the new vaccines prevented SARSCoV2 infection. Back then, the answer would determine whether I could go back inside grocery stores to pick my own produce or would have to keep playing the online-shopping-wilted-lettuce-lottery (I did not go inside stores for over a year starting in late February 2020). But the data wasn’t in because we had to wait for those first mRNA-vaccinated heroes to swim around in the world and expose themselves to the virus; only then would we know how well the mRNA vaccines worked. I remember thinking “Does vaccination with the MMR vaccine prevent infection with Measles Virus?”. For some people this might sound like a ridiculous question because hasn’t MMR driven the prevalence of measles cases down? Yes it has, it has worked spectacularly to drive cases of measles down.
Yes, vaccination for Measles Virus has driven cases of measles down greatly
But my question wasn’t “Does the MMR vaccine prevent measles [the disease]?”, because the answer to that is clearly yes. My question wasn’t about disease, it was about infection. In general, not every infection by a bacteria, fungus or virus leads to disease. As we all learned (hopefully) during the pandemic: some people can be infected with SARSCoV2 and NOT experience any symptoms. Whether or not the mRNA vaccines would completely prevent infection was an open and important question back then. My question about the MMR vaccine popped into my head because (1) despite having a PhD in Immunology I had not read the actual papers on the MMR vaccine efficacy and (2) it would boost my confidence in the mRNA vaccines’ ability to control the pandemic if I could show myself that MMR (which was wildly successful in controlling measles) doesn’t always prevent infection, because we were hearing more and more cases of people who had been vaccinated testing positive for COVID.
Please note –> I immediately got vaccinated as soon as I could. The whole point of this wasn’t about getting the vaccine, it was about the effect the vaccine would have at a population level. Was the vaccine just preventing serious COVID or was it preventing infection? Knowing how the MMR vaccine has and had worked against measles virus seemed (and is) relevant.
The answer is …well… in the vast majority of cases, MMR prevents a symptomatic infection with Measles Virus and lowers the replication of the virus to the point where they not only will not experience symptoms but they will not be able to transmit the virus to someone else. But that wasn’t a categorical yes or no was it? Lot of waffling. The interesting bits of science are always hidden in the waffles.
One thing I learned when I actually read the research on MMR efficacy was that it has worked extremely well despite the fact that it isn’t perfect. And the imperfections are really interesting. The next place to go with this is vaccine failures, ALL vaccines have them and there are two very well-studied types, primary and secondary. I should probably start my next post with how, despite being vaccinated 12 times with the Hepatitis B vaccine, I have never produced a measurable antibody against HBV. Classic primary vaccine failure.