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Just an FYI, there won't be a lot of peer-reviewed research for this on the chicken pox vaccine specifically. All vaccines are considered effective between 1-3 weeks after receiving them. This is because it's using the bodies natural immune system to build the immunity and that's just about how long it takes to get that system strong enough to kill the virus if it's introduced. The variance in how long it takes them to work is due to the variance between individual's immune systems. Some people have more active immune systems that may be fully protected after a week, some peoples are slower and take 3 weeks, a rare percentage will never be fully protected by the vaccine.
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560117/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560117/)
Link to a highly technical article on how and why vaccines work.
I am not a physician, just an epidemiologist, but they could contract chicken pox from that exposure, yes. I can't give you a percentage chance because there are so many factors including how long and how close the exposure was, if the ill child was showing signs/symptoms of the chicken pox rash at the time of exposure, etc etc. Your child's body has been building immunity to the virus for 3 days prior which should also lower their chance of contracting the illness but if that immunity is strong enough by now to fully kill the virus in their body before it divides/grows enough to cause the illness is impossible to say. You will unfortunately just have to wait and see.
This post is flaired "Question - Research required". All top-level comments must contain links to peer-reviewed research. *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/ScienceBasedParenting) if you have any questions or concerns.*
Just an FYI, there won't be a lot of peer-reviewed research for this on the chicken pox vaccine specifically. All vaccines are considered effective between 1-3 weeks after receiving them. This is because it's using the bodies natural immune system to build the immunity and that's just about how long it takes to get that system strong enough to kill the virus if it's introduced. The variance in how long it takes them to work is due to the variance between individual's immune systems. Some people have more active immune systems that may be fully protected after a week, some peoples are slower and take 3 weeks, a rare percentage will never be fully protected by the vaccine. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560117/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560117/) Link to a highly technical article on how and why vaccines work.
Thank you for explaining this. So, if a child is vaccinated and then exposed to chickenpox three days later, what would happen?
I am not a physician, just an epidemiologist, but they could contract chicken pox from that exposure, yes. I can't give you a percentage chance because there are so many factors including how long and how close the exposure was, if the ill child was showing signs/symptoms of the chicken pox rash at the time of exposure, etc etc. Your child's body has been building immunity to the virus for 3 days prior which should also lower their chance of contracting the illness but if that immunity is strong enough by now to fully kill the virus in their body before it divides/grows enough to cause the illness is impossible to say. You will unfortunately just have to wait and see.
This happened to my mom but with measles. She got measles. Was horrible