Should I worry about my 2-year-old playing with unvaccinated kids?
January 7, 2014 10:10 AM   Subscribe

I have read articles about herd immunity and I understand the concept. But, boots on the ground, should I worry about my vaccinated son occasionally playing with a partially vaccinated 4-year-old and a completely unvaccinated 2-year-old? We're all pretty mindful of staying away when the children show signs of illness. I am interested in both medical information and how other parents have navigated this potential risk.
posted by gentian to Health & Fitness (36 answers total) 3 users marked this as a favorite
What would be the point of a vaccine if it didn't protect you from potential exposure to the thing you are vaccinated against?
posted by Brockles at 10:17 AM on January 7, 2014 [3 favorites]

If your son is vaccinated, he's in no danger of contracting an illness he's been vaccinated against - just the typical cold or cough that any kid might pass to any other kid.

It's only really dangerous when multiple unvaccinated kids interact with one another. Your kid is part of the vaccinated herd. The unvaccinated kids get their protection from, presumably, only interacting with "herd" kids. The danger is when they start interacting with each other, and those preventable diseases can quickly spread as soon as they are introduced to the population.

So in other words, you're fine.
posted by trivia genius at 10:18 AM on January 7, 2014 [9 favorites]

No, that's what the vaccine is for. The other kids parents are the ones who should be worried about their kids playing with other unvaccinated kids.
posted by tylerkaraszewski at 10:18 AM on January 7, 2014 [1 favorite]

Best answer: If your son is vaccinated, he's in no danger of contracting an illness he's been vaccinated against

That is not true; no vaccine is 100% effective for a variety of reasons. That is one reason why keeping a high level of vaccination is so important; those patients for whom the vaccine doesn't work (or who can't have it for valid medical reasons) rely on the fact that those around them have been effectively vaccinated in order to avoid exposure to the disease. Now, the risk to an otherwise healthy child is small; even if they do contact the disease they will probably be OK in the long run. But there is some slight risk. Personally, I would let my daughter play with kids who weren't vaccinated on an occasional basis (she probably already does at crowded public playgrounds). A bigger concern would be why the other kids weren't vaccinated and if I wanted to spend much time around people who may have some beliefs I have a real problem with.
posted by TedW at 10:29 AM on January 7, 2014 [79 favorites]

There's a minor risk, in that no vaccine is 100% effective. But establishing overall vaccine efficacy in an environment of mixed vaccinated and unvaccinated children is super complicated. A relevant study.
posted by Andrhia at 10:29 AM on January 7, 2014 [2 favorites]

While I wouldn't actively worry, be aware that there IS a very slight chance of harm - vaccines do occasionally fail (see this Google Scholar search for some studies).

Also, seconding blue_beetle: it may seem shallow/stupid/judgmental of me, but I would never hang out with people who don't vaccinate (for non-legit reasons), nor would I let my kids hang out with THEIR kids. Not vaccinating is basically like saying "fuck you, greater good!" And that ain't cool.
posted by julthumbscrew at 10:31 AM on January 7, 2014 [13 favorites]

Mod note: Just answer the question please.
posted by jessamyn (staff) at 10:31 AM on January 7, 2014

Best answer: I would only worry about it if you or your spouse (or your kids, of course) are in regular contact with people who have compromised immune systems. This would include people with immune system diseases or people receiving chemotherapy.

Vaccines do also occasionally fail, (or perhaps wear out? idk really) not just in childhood but in adulthood. I have medical records showing my vaccination in the US for MMR and I nevertheless caught the mumps as an adult.
posted by elizardbits at 10:38 AM on January 7, 2014 [5 favorites]

Seroconversion rate for any vaccination is not 100%. For this reason I would be wary of having my kids play with willfully un- or undervaccinated children.
posted by Sternmeyer at 10:38 AM on January 7, 2014

Mod note: And do not, for any reason, turn this into a discussion of vaccinations generally.
posted by jessamyn (staff) at 10:38 AM on January 7, 2014 [3 favorites]

If you are not pregnant or planning to be pregnant soon, if you aren't in regular close contact with someone who is pregnant or planning to be pregnant soon, and if you aren't in close contact with people with compromised immune systems (the elderly, babies too young to be immunized, people with certain diseases), it shouldn't be an issue.
posted by jeather at 10:43 AM on January 7, 2014

If your son has only had one dose of the measles, mumps, rubella (MMR) vaccine, then there is a 5% chance he doesn't have immunity (Centers for Disease Control and Prevention (CDC), "Measles - Q&A about Disease & Vaccine"). The DTaP vaccines commonly used against pertussis have efficacy of 80%–85% (CDC, "Epidemiology and Prevention of Vaccine-Preventable Diseases: Pertussis") and immunity wanes over time.

Because vaccines are not 100% effective, herd immunity is an important part of protecting a population from disease.

I'm sure TedW is right. Personally I would have to consider whether the benefits justify even the small chance of disease. I doubt that they do. Also, I think that antivaxxers should be treated like anyone else who abuses a public good. Would you let your kids play with other kids whose parents let them litter all over the place? This is similar to me, but much more damaging (yet much less visible).
posted by grouse at 10:44 AM on January 7, 2014 [4 favorites]

Mod note: Seriously. Just answer the question. Answer stumping for pro/anti-vax groups will be deleted.
posted by jessamyn (staff) at 10:53 AM on January 7, 2014 [1 favorite]

Also, many diseases are contagious before there are visible signs of illness. If we could prevent disease spread by avoiding those with visible signs of illness, we wouldn't have had the measles and pertussis outbreaks of the last few years. Unfortunately, we can't.
posted by grouse at 10:53 AM on January 7, 2014 [1 favorite]

Vaccines are not 100% protective 100% of the time, so yes, there would be a risk, though slight, that your children could catch some old-fashioned disease from the unvaccinated kids. I would guess that the risk would be higher for illnesses with more recently developed vaccines, like chicken pox, as parents are more likely to consider the newer vaccines as "optional," and also for illnesses with vaccines that tend to wear off over time, like pertussis, because people are not always good about keeping up with boosters for those. So there are more people in the general population who are unvaccinated / not fully vaccinated for those, and therefore more of a chance that the unvaccinated children your children interact with will contract those diseases.

(Also, other people answering: the OP's kids could be involved in a preschool, club, playgroup, or class that these other unvaccinated children are also involved in. The unvaccinated children in question might be family members. Etc. There are a number of contexts where not interacting with these unvaccinated kids might have serious social or educational drawbacks for the OP's children, and you do not know what the context is from the OP's very simple question. So maybe try answering that question instead of critiquing the OP's social choices that you have no context for judging?)
posted by BlueJae at 10:57 AM on January 7, 2014 [3 favorites]

You're keeping your kids away when the other children are sick. Between that and the vaccinations, your kids should be quite well protected against most things that have vaccines.

Kids get sick. There's still a much greater chance of getting hand foot and mouth, a cold, or a stomach flu from the kids vaccinated or not than measles or pertussis.

Pertussis can be a problem because though, as others have said, the DTaP/TDaP vaccines aren't super-effective and pertussis can be contagious in early stages. If there's a pertussis outbreak in your area, I would suggest staying away.

But kids navigating their own social environment is an important part of growing up. I would be loathe to pick my kid's friends for my own moral reasons, even at 4.
posted by Llamadog-dad at 11:02 AM on January 7, 2014 [3 favorites]

Since vaccination is not 100% certain, then there is a chance that if your kid played with an unvaccinated kid that your child could get the disease. But.....oftentimes, even if he does get an illness that way, his case will be milder than the other kid due to the partial protection.

Also, there is another thing to consider. Do you really want to set your kid up for a lifetime of being worried about exposure to 'sick' people? I suspect that the psychological message you are sending of being worried about your child playing with those 'different' kids is probably worse than any slight chance your child might come down with a mild case of whooping cough. Just something to consider.
posted by BearClaw6 at 11:03 AM on January 7, 2014 [2 favorites]

Medically, my greatest concern would be that you or your child would end up with, say, pertussis germs on skin or clothing, before the unvaccinated children were showing symptoms, and unknowingly pass it along to someone who else is unvaccinated (such as a very young infant) or immune-compromised. If you had anyone fitting that description in your home on a regular basis, I would be very wary, but less so if you are all healthy and vaccinated and don't have many people over. I would also be less wary if you live in an area with relatively high rates of vaccine compliance, since the herd immunity will make it less likely for those children to be exposed to those viruses in the first place.
posted by tchemgrrl at 11:05 AM on January 7, 2014 [1 favorite]

I'm not any sort of expert in this, but personally, I bring my kids to events that my non-vaxxer relatives' kids are attending. When they were newborns and not yet vaccinated themselves I was more cautious.
posted by gerstle at 11:05 AM on January 7, 2014

Okay, I'll try again. No, generally speaking, this is not something to be worried about, assuming that the other children are in good health at the time of the playdate.

Again, generally speaking, a vaccinated child is less at risk of contracting an illness from a non-vaccinated child, by virture of being vaccinated. A non-vaccinated child is slightly more at risk of contracting an illness from a vaccinated child, by virtue of the vaccinated child "shedding" the virus (when the vaccine has been recently administered).
posted by vignettist at 11:19 AM on January 7, 2014 [1 favorite]

my greatest concern would be that you or your child would end up with, say, pertussis germs on skin or clothing, before the unvaccinated children were showing symptoms, and unknowingly pass it along to someone who else is unvaccinated (such as a very young infant) or immune-compromised.

I just want to add, as an adult who has had pertussis, that with pertussis specifically the immunity confered by childhood imunization only lasts about 30 years, so if you are in your mid-30s or older the real bigger concern would not be your kids getting sick from their kids, but your kids conveying the illness to you.
posted by anastasiav at 11:21 AM on January 7, 2014 [7 favorites]

Your children are way more likely to be the OK ones in this scenario, they are vaccinated, the chances of the vaccine not taking are relatively small. However I'll second anastasiav and also along that note are you sure your vaccinations etc are all up to date and that the friends kids don't visit if you have elderly or autoimmune compromised friends or family members over.
posted by wwax at 11:27 AM on January 7, 2014

Avoid un-vaccinated kids. The problem is that, even though your kid is up-to-date on shots, he is at risk of catching things he is not yet vaccinated against. Unvaccinated kids also tend to have unvaccinated older siblings which magnifies their chances of having the preventable diseases early. I also would not trust an anti-vaxxer parent with the care of my kid.
posted by w0mbat at 11:31 AM on January 7, 2014 [2 favorites]

From the position of the unvacinnated child (or adult) there is some risk of becoming infected from contact with a person who recently received a live-virus vaccine. Oral Polio vaccine comes to mind. My kids' pediatrician asked specifically if my in-laws were vaccinated when they came for a visit after my little one received the OPV, since my in laws were from Eatern Europe, and their vaccination records were lost in the turmoil of war.

And of course the classic risk is to infants, who cannot be vaccinated against pertussis until they are 6 months old. They depend on the herd immunity supplied by the rest of us.
posted by citygirl at 11:31 AM on January 7, 2014 [1 favorite]

I would look into vaccination rates in your community in general. If they are quite high, then herd immunity means even these un/undervaxxed kids should be somewhat protected and the risk for your child is low. Of course even if the general community has a high rate, if these kids hang out with a lot of other non-vaxxers then they could still be at noticeable risk.

Either way whenever there's an outbreak of something those kids haven't been vaccinated against, keeping your kids away seems sensible.
posted by nat at 11:53 AM on January 7, 2014 [1 favorite]

I agree with nat - do the unvaccinated kids hang around with a lot of other unvaccinated kids? If so, they're at higher risk of contracting something (and passing it on). But if they're the lone weirdos in this situation, you don't need to worry too much.
posted by mskyle at 12:09 PM on January 7, 2014

I took steps to minimize our exposure to unvaccinated friends' children when I had a young baby in the house. I also asked those adults who wanted to be around the new baby to renew their TDAP vaccine as most adults who received a vaccination against these diseases no longer are protected as the immunity fades over time. So you may want to make sure that in addition to your kids being vaccinated, you and your partner are up to date on your immunizations as well.
posted by bq at 12:17 PM on January 7, 2014 [4 favorites]

Best answer: I faced this question in spades when we enrolled our daughter in a school with a fairly high population of anti-vaxxers. We agonized over this choice, because this wasn't occasional exposure, and we couldn't keep her away when other kids were sick. In a school there's always someone sick. We ultimately decided that we'd vaccinated her, and were willing to travel to countries with even higher levels of unvaccinated kids (France, Morocco), and that ultimately living life was more important than protecting against very small risks.

For perspective, we're both trained as scientists, my husband is a doctor, and we're politically very pro-vaccination. And this was our conclusion. And as anastasiav urges, we're pretty neurotic about getting our own vaccinations regularly, so that our daughter or her friends don't inadvertently bring home pertussis, the flu, chicken pox, or something else. As far as educating our daughter, now that she's ten, we have these discussions regularly, so that when she's old enough, she can make her own decisions regarding how a person's political positions affect her relationship with them.
posted by Capri at 12:57 PM on January 7, 2014 [5 favorites]

There's a household I go to weekly where not only are the kids not vaccinated, but the parents aren't either. My personal policy is that, since my kids and I are all in good health, up-to-date on our vaccinations, and don't have anyone immunocompromised that we see regularly, we're probably fine.

If there's a measles outbreak, or similar, I plan on not going to that house for a bit.
posted by The corpse in the library at 1:32 PM on January 7, 2014

Best answer: I grew up as a semi-unvaccinated child and a) never caught any of the things people get vaccines for and b) didn't know anyone who caught those things.

You have to look at the numbers and the risk -- for example, the CDC says there are on average 265 cases of mumps in the US every year. There are 314 million people in the US. Any individual has a higher risk of dying in a car crash (40,000/year), or on a train (931/year) than contracting mumps. So sure, you can reduce a minuscule risk to slightly more miniscule. But are you also going to keep your kids inside all the time and never drive anywhere to reduce the risk of them dying in a car crash? Are you going to let them learn to ride bikes, or not allow that to mitigate the risk of them dying in a bike accident (695/year). Point is, you can't keep your kids away from every single danger without reducing their quality of life. (Reference on statistics.)
posted by DoubleLune at 1:50 PM on January 7, 2014 [1 favorite]

I was all set to say that even if your children did catch a disease they had been vaccinated against from these unvaccinated children, it would probably be a much milder case because of partial immunity conferred by their vaccination.

But then I ran into a study of the 2009 H1N1 influenza pandemic in Nature Medicine which found that pre-existing partial immunity made that flu much worse in some cases:
Pandemic influenza viruses often cause severe disease in middle-aged adults without preexisting comorbidities. The mechanism of illness associated with severe disease in this age group is not well understood1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Here we find preexisting serum antibodies that cross-react with, but do not protect against, 2009 H1N1 influenza virus in middle-aged adults. Nonprotective antibody is associated with immune complex–mediated disease after infection. We detected high titers of serum antibody of low avidity for H1-2009 antigen, and low-avidity pulmonary immune complexes against the same protein, in severely ill individuals. Moreover, C4d deposition—a marker of complement activation mediated by immune complexes—was present in lung sections of fatal cases. Archived lung sections from middle-aged adults with confirmed fatal influenza 1957 H2N2 infection revealed a similar mechanism of illness. These observations provide a previously unknown biological mechanism for the unusual age distribution of severe cases during influenza pandemics.
This is only for the flu, and I didn't find similar results for any other infectious disease, but I can't see why the same mechanism could not come into play for other infections.

I think I'd be a little hesitant to let them play with the unvaccinated kids if I were you.
posted by jamjam at 1:59 PM on January 7, 2014

This is something we've wrestled with extensively. We have a very close friend with a compromised immune system, and I work with newborns, so it's not academic for us. We ultimately decided that, for now, we're going to limit our children's exposure to unvaccinated children, because of the concern for carrying diseases. But we live in a place where "herd immunity" is kind of a joke among certain parts of the population, including the homeschooling kids we're likely to want to hang out with. So we're the assholes who ask about vaccinations before setting playdates. (We also ask about illness, for the same reasons.)

If you don't have a lot of exposure to immunocompromised people, and/or the unvaccinated children are mostly interacting with other vaccinated people, the risk of harm is low, and it's probably fine.
posted by linettasky at 2:38 PM on January 7, 2014 [3 favorites]

Your children are vaccinated, which is all you can do to protect them. Let them play with the other children - they'll benefit from the play and the social activity and you have very, very little to worry about as far as illness from non-vaccinated kids. For that matter, your own children could pick up pinkeye or a cold virus from a grocery cart and give it to the unvaccinated kids. You can't stay away from exposure to bugs and neither can you keep your kids away from it. In the long run, exposure to minor bugs strengthens the immune system, so relax and be happy and let the kids play.
posted by aryma at 7:59 PM on January 7, 2014

Most diseases children are vaccinated against are very rare in the US. For instance, there are typically no more than 60 cases of measles or Hib per year in the whole country. So even though the risk of getting one of those diseases is slightly higher if you spend time around unprotected people, the overall risk is still very low. Not worth worrying about, to me.

Pertussis is probably the vaccine-preventable disease your kid is most likely to actually get (10,000 to 40,000 cases per year in the US), but unvaccinated kids aren't the main transmission risk to your kid - adults are. The vaccine's effectiveness decreases over time and even getting the disease doesn't provide lasting protection, so most adults are susceptible to pertussis. There's not much point avoiding unvaccinated kids in an attempt to avoid pertussis unless you also quiz all the adults you spend time with about whether they've had a recent pertussis booster and avoid the ones who haven't.

And even if you don't take all those unprotected adults into account, because the vaccine is quite a bit less than 100% effective, there are more unprotected vaccinated kids than there are unvaccinated kids. If you assume a vaccination rate for pertussis of 94% and an effectiveness of 80% (figures that seem at least roughly accurate based on some quick research), then in a population of 1000 kids you'd expect 60 unvaccinated kids and 188 kids who were vaccinated but still susceptible to pertussis.
posted by Redstart at 8:45 PM on January 7, 2014

The important thing is to minimize your children's contact with people who are known to be sick or within the incubation period after a known exposure. The vaccination status of these people isn't really important except insofar as it modifies the probability that these people are sick.

My only concern is that these unvaccinated kids may have been deliberately exposed to various diseases as a sort of DIY vaccine. In some circles, anti-vaccination parents have revived the practice of "pox parties" and the like so that their children acquire the immunity "naturally."
posted by d. z. wang at 9:11 PM on January 7, 2014

Just to add to your thoughts....I've been vaccinated and re-vaccinated and re-vaccinated again for rubella/German measles. It agonisingly delayed cycles of IVF for us. The reason is because I'm someone that the vaccination just doesn't take with.

So my pregnancies were knuckle clenching. I wasn't immune compromised (but one of my kids is) and not an infant, but still at risk. I'd have been an invisible person at risk to a lot of parents back then. It made us definite that we didn't want to be around unvaccinated people, or in crowded confined spaces. It's now something we consider in our friendships because I'm sure there are a lot of people like me that the vaccination just doesn't work for.
posted by taff at 2:23 AM on January 8, 2014

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