Each of us has special sensitivities. Some have peanut allergies…some get lots of strep throat….and a very, very few get serious reactions to vaccines. I wish we had a test to detect which infants are susceptible to severe measles or big vaccine reactions, but no such test exists.

The good news, however, is that shot risks are tiny compared to the risks of full-blown illness. For example, influenza and chicken pox hammer the immune system 100-1000 times harder than the impact of the flu or pox vaccines. While most kids breeze through the chicken pox shot, even a mild case of real pox can weaken a child’s immunity for weeks to months and lead to ear infections, pneumonia and, rarely, toxic shock syndrome. (And, it can often land an adult in the hospital!)

There is one special case of possible vaccine susceptibility that made headlines last year and became a major new focus for those who claim vaccines cause autism. A 19-month-old child developed autism after getting 5 shots. But – and this is a huge “but” – unlike most autistic kids, this one child also has a rare medical problem - Mitochondrial Disease (MD).

Recently, vaccine avoiders have floated the theory that perhaps many healthy looking kids have hidden MD. They suggest that it may be the combination of vaccines plus hidden MD that is triggering autism in so many seemingly normal children. But, the research suggests that this is unlikely to affect more than a handful of kids. Here’s why: MD is rare (1 in 5-10,000 children). A Portuguese study found ~93% of autistic children had no evidence of MD (and even that 7% figure has yet to be confirmed).

In a recent study, scientists from Harvard and Johns Hopkins could find only 25 children with both MD and autism. And, these kids had serious problems rarely seen in most cases of autism (like, delayed walking, acid reflux, liver disorder, severe fatigue, etc). Fourteen of these kids seemed to be developing normally then suddenly deteriorated into autism during toddlerhood. But only 1/14 (7%) got worse right after shots. (Had 2 or 3 or 5 kids gotten worse after the shots, one could make the argument that children with MD are at increased risk for getting autism after vaccinations.

However, as I mentioned in part 1 of this blog, 7% is very close to the number of cases one would expect to be diagnosed right after shots…just by chance.) Another dramatic finding of this study argues against a link between MD and the national rise in autism incidence: classic autism spectrum disorder affects many more boys than girls (3-9 times more boys!)…but children with Mitochondrial Disease + autism are evenly split between the genders.

While it remains to be proven that children with MD are more vulnerable to shots, there is no doubt that they are super-vulnerable to illness. In other words, MD kids who skip shots can get very sick, very fast it they catch a vaccine preventable disease like influenza or pneumonia.

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Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider. Breastmilk is the best source of nutrition for babies. It is important that, in preparation for and during breastfeeding, mothers eat a healthy, balanced diet. Combined breast- and bottle-feeding in the first weeks of life may reduce the supply of a mother's breastmilk and reversing the decision not to breastfeed is difficult. If you do decide to use infant formula, you should follow instructions carefully.