Your unvaccinated kid can't play with my vaccinated kid.

I’ve heard the argument time and time again from parents who choose not to vaccinate their children: “If your child is vaccinated, why are you worried about him catching anything from my unvaccinated child?”

To most people, this would be a pretty compelling argument. After all, my kid is protected, so who gives a lick about your kid. Neither is a threat to the other, right?

What many parents don’t understand (or flat-out deny) is that, while vaccinations are highly effective and greatly decrease the chance of contracting preventable diseases, no vaccine is 100% effective. The CDC reports that “most routine childhood vaccines are effective for 85% to 95% of recipients. For reasons related to the individual, some will not develop immunity.”

Therefore, during an outbreak of a vaccine-preventable disease, those unvaccinated children can and do increase the risk of disease for everyone that may have been exposed, even if the people who have been vaccinated greatly outnumber those who have not. While a small portion of the vaccinated population may be affected, this does NOT prove that vaccines are ineffective.

To gain a greater understanding, we have to look at the percentages involved. A great example of this has been provided by the CDC:

In a high school of 1,000 students, none has ever had measles. All but 5 of the students have had two doses of measles vaccine, and so are fully immunized. The entire student body is exposed to measles, and every susceptible student becomes infected. The 5 unvaccinated students will be infected, of course. But of the 995 who have been vaccinated, we would expect several not to respond to the vaccine. The efficacy rate for two doses of measles vaccine can be higher than 99%. In this class, 7 students do not respond, and they, too, become infected. Therefore 7 of 12, or about 58%, of the cases occur in students who have been fully vaccinated. 

As you can see, this doesn't prove the vaccine didn't work - only that most of the children in the class had been vaccinated, so those who were vaccinated and did not respond outnumbered those who had not been vaccinated. Looking at it another way, 100% of the children who had not been vaccinated got measles, compared with less than 1% of those who had been vaccinated. Measles vaccine protected most of the class; if nobody in the class had been vaccinated, there would probably have been 1,000 cases of measles.

I for one am grateful to be able to give my son the possibility for immunity against communicable diseases such as, but certainly not limited to, measles. Considering the example above, though, and what’s going on in our community today (one small example is a recent outbreak of pertussis in Virginia, which is scarily close to where we live in Maryland), I am scared shitless for my son and, thinking about it on a grander scale (some might call it a socialist mindset!), for others’ children.

After all, it’s the unvaccinated crowd that has reintroduced and continue to introduce the disease into our communities. The many examples going around recently serve to answer why a vaccinated person may be concerned about contracting a disease from the relatively small – but continually growing – unvaccinated sect of the population.

As much as anti-vaccinators want to deny it, it’s herd immunity that has allowed them the privilege to choose whether or not to vaccinate their children. After all, if enough people are vaccinated, then I don’t have to worry about my kid, right? Right!

... wrong. Considering how rapidly the number of anti-vaccinating parents is growing, I imagine we’ll soon fall below the recommended threshold of 85% of the population being vaccinated to guarantee herd immunity. And that could come with some very scary results.

I recently came across an interesting simulation that shows just how herd immunity works. I really encourage you to try it, if only because it’s an interesting show of how statistics work. You can see how, sure, some of the vaccinated population will be affected by a disease, but for the most part, so long as it remains over 85%, the rate at which the disease catches on is actually quite low. (To try, you’ll need to enter “0.85” for “immunization rate” on both the right and left.)

When putting in a lower vaccination rate (say, 0.8 or lower), the disease spreads more rampantly, guaranteed to affect all of the anti-vaccinators while taking some vaccinators along with it, considering the 5-15% margin of error for vaccine effectiveness.

This is unacceptable. As it stands, in the modern first world, measles itself has a mortality rate of 1 to 3 deaths per 1000 cases, depending on the country and the study. There is no study that says anything lower than 1:1000. And if we were to get down to the actual reason why we should be concerned about herd immunity, it’s meant to protect those who literally cannot have vaccines, such as the immunocompromised or babies too young to be vaccinated.

Herd immunity is NOT meant to protect those children whose parents decide, based on false “science” and other woo, that vaccines are so dangerous that having them is worse than contracting an otherwise preventable disease.

As for the vaccines being dangerous, the numbers speak for themselves, especially when compared to the dangers of the infectious diseases they prevent:

DISEASE 

Measles 

Pneumonia: 6 in 100
Encephalitis: 1 in 1,000
Death: 2 in 1,000 

Rubella 

Congenital Rubella Syndrome: 1 in 4 (if woman becomes infected early in pregnancy) 

VACCINES 

MMR 

Encephalitis or severe allergic reaction: 1 in 1,000,000 

DISEASE 

Diphtheria 

Death: 1 in 20 

Tetanus 

Death: 2 in 10 

Pertussis 

Pneumonia: 1 in 8
Encephalitis: 1 in 20
Death: 1 in 1,500 

VACCINES 

DTaP 

Continuous crying, then full recovery: 1 in 1000
Convulsions or shock, then full recovery: 1 in 14,000
Acute encephalopathy: 0-10.5 in 1,000,000
Death: None proven

To clarify, this post is not meant to change anyone’s mind on whether or not to vaccinate. I wish it was that easy, but for the most part, those parents who decide not to vaccinate will not change their minds, regardless of the facts, science, and evidence used to convince them otherwise, nor the way those facts are presented. Sobering, isn't it? So this is not a post of conviction.

Instead, this is a note to all those anti-vaccinating parents out there. Before we hang out with you, before I potentially expose my child to yours, I will ask whether your child is vaccinated. I will decide whether or not my child is safe around yours, considering your answer. And I will pull my child from the situation, regardless of where we are or who is with us, if you are an anti-vaccinator.

Because considering these numbers, and considering how many whackjob parents Tycho and I will inevitably come across where anti-vaccinators’ children are allowed to roam free (including but not limited to his daycare and school), I simply cannot take the risk.

Vaccine denial is dangerous. And I will never knowingly put my child in danger.