Question: Hypothetically, If you were to have 4 children and one of them wasn't vaccinated, would it be dangerous for the other 3 kids being exposed to that one child unvaccinated or is that one child at risk from contracting somethings from the other kids?

  1. Hi jaxterjohns

    What a thoughtful question 🙂

    Let me try to deconstruct my answer into pieces… and get over my sadness that hypothetical 4th child has missed out 🙁

    Firstly, that 4th child is at risk of getting the disease, whereas the 3 others are protected (yes… I hear you cry – that’s obvious. Bear with me – I like to get all the facts out on the table first)

    The basic scenario is that unvaccinated child 4 is mainly at risk of getting disease from other, unvaccinated children who already have disease and the 3 vaccinated ones are protected.

    BUT… the story is actually much more complex in reality: Lets imagine the following scenarios:

    They go to the playground and 4th child comes into contact with the disease and gets sick. The first problem is that even though the others are vaccinated, there are always tiny tiny chances that the vaccination wont work 100% so (although unilikely) this 4th child, now sick is putting the others at a slightly increased risk.

    Then, on the other side of the coin, the 3 vaccinated children are playing with kids who have the disease but don’t know it. They don’t LOOK sick, but they are. The 3 vaccinated kids then carry the disease back to the 4th, unvaccinated child and then that child gets sick.

    Hope this makes sense! Thanks for a great question! 🙂


  2. Hi jaxterjohns,

    I think that, with most diseases, you can only pass on the disease if you contract it yourself. That is, because I’m vaccinated against X, I don’t contract X even if I meet a person with X, and therefore I can’t pass on X to someone else. (OK, now that I’ve read Kate’s answer [we were typing at the same time], it seems that you can pass on a disease without falling ill from it yourself. Perhaps Kate knows whether this can only happen with a small fraction of diseases?)

    But the unvaccinated child is definitely at risk of contracting the disease from someone other than its brothers/sisters. And since people in the same family will meet a lot of the same people, the unvaccinated child would contract a disease from someone outside the family while its brothers/sisters would be protected.


  3. Yes – that one child would be at risk of getting the disease….but also would be at risk of passing that disease on. if they were all vaccinated, this would minimise the opportunities for the disease to be spread!

    The important issue with vaccination is, to reduce or minimise the occurrence of the disease, as many people as possible need to be vaccinated. there are diseases around today that could have been wiped out if more people were vaccinated.



  1. Thanks guys, your answers has helped me out so much with my research. 🙂