chicken pox transmission

[MCKH]

Does the chickenpox vaccine prevent transmission? (i.e. would an exposed but vaccinated older sibling be a risk to an unvaccinated infant sibling?)

[MissRubyandKen]

It is possible for a vaccinated child to contract chickenpox, usually a milder form, often less than 50 lesions, possibly even atypical, and be contagious. Read the package insert and CDC's pink book chapter. It is also possible to get chickenpox from someone vaccinated with the varicella vaccine, though primarily if they show symptoms, ie. rash, and the infected may not seroconvert. My dd got the virus from my son who was vaccinated, then showed symptoms of rash and fever a couple of weeks later. If you're asking can the vaccinated child pass on the virus without symptoms I'm sure it is possible, but it would be anybody's guess how likely, probably not very. We know people who are exposed who had the virus can be reinfected and therefore boost their natural immunity, and that the virus has the capacity to persist in the body after infection as a latent infection.

[mamakay]

The CP vaccine might only be about 50% effective (with one dose) so...maybe. But when it works, it prevents transmission. If the older sibling has had more than one dose, the chances that it'll be effective go up.