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Some parents don't want their children to hang around unvaccinated children.

An anti-vax argument I've heard is that this suggests the parents believe the vaccines are not effective, if potentially being exposed to the disease still concerns the parents.

Here's one typical example of this common claim, quoted in this ScienceBlogs article, which itself quotes from various different anti-vaccination sites:

This is the part I’ll never understand… if the parents who vaccinate their children have such confidence in the vaccines themselves, then an unvaccinated child could never harm their protected child. Which one is it? Do they believe that vaccines work with all kids 100% of the time or don’t they?

Is that correct? That ScienceBlogs article does offer a brief counter-argument, based on the fact that "Vaccines are not 100% effective", but mostly discusses the pro- and anti- vaccination debate generally rather than focusing on the evidence for or against this claim specifically.

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Vaccines are effective, but no vaccine is ever 100% effective. A large benefit of them is herd-immunity, meaning that the risk of infection is reduced by greatly reducing the likelihood that people you interact with are carriers. If there is no herd immunity (because most of the people around you aren't vaccinated) then your risk of infection goes up even if you are vaccinated yourself. – GordonM Jul 19 at 15:40
I'd just like to add - every case of a disease that spreads is another chance for a mutation to develop that will render the vaccination moot. – Zibbobz Jul 19 at 20:19
up vote 50 down vote accepted

The answer is sometimes YES, vaccinated people are sometimes afraid of unvaccinated people, often with good reason. This in no way suggests the vaccine is not effective if potentially being exposed to the disease still concerns the parents of vaccinated children.

I blended my two comments into an answer.

Dr. Jodi Halpern wrote (from Ask the Experts: Should Schools Require Vaccines?).

Most parents of unvaccinated children believe they are trying to protect their child from vaccines' possible harm, despite medical evidence to the contrary. I've talked to parents who are terrified that vaccines will worsen the neuropsychological conditions of children with existing problems. They don’t want to put other children at risk. Rather, they are saying, 'We have a different belief system than the state, and the state cannot impose its beliefs on our family.'

Yet there is no doubt that an unvaccinated child infected with measles could inadvertently harm other children, especially ones who can't be immunized because they have low immunity due to illnesses like cancer. So there’s an ethical and fiduciary responsibility that lies with the school. There are basic conditions to have a civil society, and one of them is collaboration. For parents to send their children to school, they have to believe that the schools are full fiduciaries for their children. They have to trust that the school will not harm their children.

You wouldn't send your child to a school with broken glass, rusty nails, or dangerous equipment on the playground. You expect the school to keep its grounds safe. In the same way, when you send your young children to a public school, you expect that the school will protect them from preventable, serious diseases. If your children are going to be put at risk for a serious disease like measles, then the schools are not being an adequate fiduciary.

For this reason, public schools do have an ethical obligation to require students to get vaccinated unless they are immunocompromised and can't for medical reasons. This does not mean that the state has the right to forcefully vaccinate children against their parents' will. But it does mean that some children whose parents don't believe in vaccines may not be able to attend public schools during measles outbreaks if their presence would put other students at risk.

I think above is the basis of the answer. Yes, some parents of vaccinated children do fear it as their other children may die. Now anti-vax groups may spin this as evidence that people with vaccines are worried they may not work! This is spin. A small group of parents of vaccinated children fear it with very good reason. One of their children may die.

So you have two children: (A) one healthy 10 year old child vaccinated, and (B) one 12 year old child with a serious illness that would result in death from a common disease we vaccinate against (as stated in the above quote) but who cannot be vaccinated due to their illness. Do you want (A) hanging out with an unvaccinated child? Fear = Yes, as (B) could die! Let's say it is only 1% chance of your vaccinated child bringing home the disease. Do you want to take that 1% with your other child's life! See @Roger comment with the bulletproof proof vest analogy. Vaccines are not 100% we rely on the herd immunity that these unvaccinated children can destroy.

Additionally, I think many parents would not want to associate with these children's parents (parent to parent not child to child as your questions asks). I would consider someone who holds back vaccines for no proven medical reason as ignorant (similar to a racist or bigot) so I would not want to associate with them and I would not want my child to overly associate with their child, say at a sleepover as their parents have already demonstrated very poor decision making. This could be extrapolated into, "parents with vaccinated children don't want them to hang around unvaccinated children" but it is not fear.

Some additional resources to back up my answer.

"Why I won't let unvaccinated people around my kids", CNN

"To the Parent of the Unvaccinated Child Who Exposed My Family to Measles", Mother Jones (--Just a note before reading this the story is quite harrowing).

Just of the top of my head I can come up with at least 10 reasons I would fear my child hanging out with an unvaccinated child. For brevity I will not list them all but one is if any member of my household worked on a children's cancer ward.

*Please note: The bold items are to highlight the specific related claims are not highlighted in the original quoted text.*EDIT - I am going to update the answer as the question has changed a little.


In 2000, "The US Centers for Disease Control and Prevention (CDC) declared endemic measles eliminated in the USA" according to Gostin, L. O. (2015). Law, Ethics, and Public Health in the Vaccination Debates: Politics of the Measles Outbreak. JAMA, 313(11), 1099-1100. Chicago

However, vaccine-preventable diseases (eg, diphtheria, pertussis, tetanus, measles, mumps, and rubella) are increasing, with some parents delaying or selectively immunizing their children and, at times, even opting out of having their child immunized. In 2014, the United States recorded a record number of measles cases—644 cases from 27 states, more than 3-fold higher than any previous year since 2000. As of February 6, 2015, the CDC has reported 121 measles cases in 17 states, mostly from an ongoing outbreak linked to an amusement park in Orange County, California. Most cases were unvaccinated (55%) or of unknown vaccination status (31%).

This quote is interesting pertaining to the original question.

“Their children have been sent home from school. Their families are barred from birthday parties and neighborhood play dates. Online, people call them negligent and criminal.” (Healy J, Paulson M. Vaccine critics turn defensive over measles. New York Times. January 31, 2015:A1.)

Finally, evidence to the contract often forwarded by the antivacs has been debunked.

Reiss, Dorit Rubinstein. "Herd Immunity and Immunization Policy: The Value of Community Protection." Oregon Law Review 94 (2015). whi state,

This article explains why claims made by Holland and Zachary in their article, Herd Immunity and Compulsory Childhood Vaccination: Does the Theory Justify the Law?, are incorrect and untenable. Their view of herd immunity is also incorrect: the article does not well define the term, ignores data showing that herd immunity works, and their discussion of their two examples is inaccurate: close examination of those examples actually shows the role of herd immunity in protecting against disease.

I should note the question has changed since I posted this answer so it may not seem to be a perfect 'fit' now but it was when the question was asked.

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This doesn't show any sense of "afraid". They ought to be afraid given the risks, but I don't agree that any examples of "fear" has been shown here, especially in light of the difficulty of determining whether someone is anti-vaccine or not. People can fear things that are rightly dangerous, but many people also fear things that are not especially dangerous (lightning) and don't fear things that are pretty dangerous (cars). – March Ho Jan 20 at 22:46
@MarchHo I am not really sure what you are saying here. Can you explain more? I am having trouble with, "but I don't agree that any examples of "fear" has been shown here," Have you read the two links?those people are dripping with fear and one actually concludes, "thanks for exposing 195 children to an illness considered 'eliminated' from the US. Your poor choices don't just effect your child. They affect my family and many more like us. Please forgive my sarcasm. I am upset and just a little bit scared." – If you do not know- just GIS Jan 20 at 23:01
Good answer, two possible improvements: 1) your example with the two children is good, but a much more common example would be where child A is vaccinated and child B is not yet old enough to be vaccinated. Child A playing with an unvaccinated child could result in child B becoming infected. Your example with an unvaccinateable immuno-deficient or allergic child is good, but relatively rare. Having a very young sibling, however, is very common... – user568458 Jan 21 at 9:32
...2) there's also the fact that unvaccinated people can act as a reservoir in which viruses and bacteria can mutate. For example, if measles reaches a school where everyone is vaccinated, it has one chance to infect kids, then dies out. 99.9% of times it'll fail. If there's a large enough community of unvaccinated children, the virus can circulate and persist amongst them for days, weeks or months. Viruses are constantly mutating, and if at any point in this time it mutates into a form the vaccine is less effective against, the mutated strand could hit the vaccinated kids, survive and spread. – user568458 Jan 21 at 9:38
Would be worth noting that, because vaccine only helps with immunology system, even vaccinated person can get sick if it happens to get immunodeficiency. Transplants? Malnutrition (anorexia)? Cancer? That are bad conditions easily turn into death by illness their subject was vaccinated against. I know Wikipedia is not a scientific resource, but it's decent as a starting point for reading, especially references. – Mołot Jan 22 at 0:37

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