MS Patient, Ph.D.: Is It Too Early to Get Excited About the BCG Vaccine?
I have concerns about the explanation for the results of the study, and my own experience suggests widespread use of BCG may have unintended consequences.
The new BCG vaccine study caught my attention for all the wrong reasons.
The thing is, I have a knee-jerk reaction when it comes to the BCG vaccine. I say this because it brings to my mind the frustration that I felt as a child when I was forced to take a 6-month “preventative” course of isoniazid pills, because of a positive tuberculosis skin test that was mistaken for a latent TB infection. I attribute the treatment to overly cautious health providers wary of foreigners bringing in TB, since the U.S. isn’t used to healthy individuals that have received this vaccine. In my case, I had just moved from my home country of Argentina, where BCG is part of the normal vaccine schedule, and showing them the characteristic raised scar in my left arm was not enough to get me out of the treatment. So when I read about this study, my first thought was to be wary of whether the U.S. health care system would be able to handle a sudden increase in patients given an uncommon vaccine. My particular extreme situation may not happen to everyone, but if all new patients diagnosed with MS were to receive this vaccine I would expect some added inconvenience, either having to undergo TB skin tests or frequent chest x-rays to exclude a TB infection. In fact, patients might be similarly inconvenienced in other countries outside the U.S. as well; anywhere the BCG vaccine is not widely used.
Keeping my particular bias against BCG aside, my second thought was to be skeptical of what sounded like an improperly controlled study with few subjects, small effects, and lofty implications. But, after reading Jennie Dusheck’s excellent summary of the study, she convinced me that this particular clinical trial was actually well designed. Although the study’s results are intriguing, there isn’t a great, evidence-based explanation about how the BCG vaccine works at reducing the number of new lesions. The authors don’t try to determine a mechanism of why the treatment works, although they speculate on some possibilities. (I won’t go into the details, but I don’t find them very convincing.) At this point, there are more questions than answers and, although statistically significant, I think the sample size is still too small to get too excited about the findings.
In any case, I generally don’t like the “well, we don’t know exactly how this works … but it does, so take it” clinical findings. But if I allow myself to be persuaded, I would want to apply the lessons from this study to my current life. I find myself thinking: Would this vaccine work for me? What about the risks of taking a live vaccine as a person living with MS? Should I not worry and take it, or other live attenuated vaccines that also elicit CD4+ T cells, since they could potentially prevent new lesion formation?
In short: No, of course not!
The more nuanced answer is that I shouldn’t try to apply recent, albeit intriguing, research or clinical findings to my life right now. These results might not stand the test of time. There’s still A LOT more data to be acquired before any of this can be used in the clinic. I get it; research moves slowly and incrementally. But no matter how promising something sounds, we need to wait for larger human studies to yield positive results before we apply them to ourselves. In this particular case, I think we need to be skeptical and really try to get a more concrete explanation of the mechanism behind the finding. I think there’s probably some very interesting immunology at play here, and figuring it out could be more helpful in the long run to our understanding of MS disease initiation and progression.