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Chickenpox Vaccine Risk for Sibling?
Q: I have a four year old who will be getting the chickenpox vaccine. I also have a nine month old. Is it possible for the nine-month-old to catch chickenpox from her vaccinated sister?
A: Yes, it's possible, but not very common at all. Your question is one that many people ask since the chickenpox vaccine is made in the lab from "live" virus particles. The chickenpox vaccine does protect well against the disease. It is attenuated (weakened) so as not to regularly cause the disease in the person getting it or in anyone exposed to that vaccinated person.
With this in mind, realize then that it is extremely rare for someone who gets the vaccine virus to spread it to another individual who does not have any protection against chickenpox. In fact, there are only three documented cases of chickenpox out of more than 15 million doses of vaccine given to date that were transmitted to healthy people from recently vaccinated people. These three cases ended up being mild disease and there were no complications. More importantly, this type of spread has only been documented when the person receiving the vaccine develops a chickenpox-like rash right after their shot.
Since the chickenpox vaccine was licensed in the U.S. in 1995, recommendations to promote wider use of it have expanded. Some states require children entering school who have not had the disease before to receive the immunization. Chickenpox vaccine is not recommended for children who cannot fight infection well, have cancer, are taking large doses of steroid medicines, or for women who are pregnant. So the bottom line is I would suggest your 4-year-old receive the vaccine, assuming everyone is healthy and well in your family. It is very unlikely she will spread it to her infant sibling.
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Henry Bernstein, M.D., is currently the associate chief of the Division of General Pediatrics and director of Primary Care at Children's Hospital, Boston. He also has an academic appointment at Harvard Medical School.