What has led to this new epidemic of fear? The answer is complex, involving a convergence of multiple factors: a lack of understanding of how science works, mistrust in medicine in general and in expert advice even more generally, mistrust in government oversight and the pharmaceutical industry, and a growing counter-culture trend, particularly in more highly educated socio-economic populations. The most common vaccine concerns can be summarized as follows:

1. Vaccines have been linked to autism – While this is true, vaccines have been linked to autism, they don’t actually have anything to do with autism. I will not tackle this myth here, but suffice it to say, not a single shred of valid scientific evidence has ever been put forth to support a causal link between vaccines and autism. However, volume upon volume of excellent, peer-reviewed data has unequivocally shown no such a linkage [for a complete set of references, see the references section of this post from the Science-Based Medicine blog].
2. Vaccine ingredients, like thimerosal, aluminum, squalene, and others can lead to immunological and neurological consequences in infants – Again, no valid data exists to support such a belief, and the existing science points us in the opposite direction.
3. Too many vaccines can overwhelm an infant’s immune system, leading to a host of disease conditions – This is absurd on its face to anyone familiar with basic immunological principles. All of the childhood vaccines combined, are but a mere drop in the bucket compared to the immunological challenges an infant faces every day. Not only can an infant’s immune system easily handle the combinations recommended in the routine schedule, but the number of immunologic stressors, if you will, contained in the current schedule (that enormous, and growing list the anti-vaccine community complains so much about) has actually been decreasing due to improved vaccine technologies ^[2].