I encounter, time and time again, anti-vax parents who tell me that the vaccinated children are the ones who are actually dangerous, as the vaccine "sheds" and infects non-vaccinated children. One mother, whose child acquired rubella because she was unvaccinated, actually blamed the disease on a vaccinated child in the school who had received her MMR shot. Could you explain this? I'd like to have an answer at the ready. Thanks again!
Some "live viral" vaccines do indeed shed, i.e. the vaccinee makes the virus particles and excretes them for a while.
Rubella is one of the viruses that will be excreted, HOWEVER, it is not transmitted in casual contact between kids or a vaccinated child to an adult. The only situation in which transmission has been found is when the freshly vaccinated mother breastfed her baby (in this situation, a quart or so of virus-containing fluid is consumed by the baby).
Measles vaccine is not shed, Jeryl Lynn Mumps strain (which is used in the US and Western European mumps vaccines) is not transmitted.
Varicella does shed and transmission has been documented, however, in much rarer cases than is usually claimed on vaccine boards (where you get the notion that vaccine-induced chicken pox is running rampant through our Kindergartens and schools).
The old polio vaccine, the OPV, could shed and transmission has been recorded to immuno-compromised people.
The first dose of rotavirus vaccine can shed, but since the transmission route is oral-fecal, the risk to other children would be low, due to the young age of first vaccination (6 to 10 weeks) and the lack of mobility and direct contact between kids that age.
Can post literature if you want, but I am having guests over Easter, so no time now.
MWV, In addition to what Catherina stated, actual secondary transmission is extremely rare and the live flu vaccine can also shed. Infection is more mild and does not confer much in the way of immunity; this is true for all of the live vaccines that can shed and cause secondary infections.
Thank you both so much for "shedding" some light on this (sorry!). Having specific information like this helps parents who vaccinate so much when we encounter claims like this. To put it into perspective is crucial, and new and expecting parents need that perspective. Of course, nonvaccinating parents wouldn't have to worry about Little Johnny contracting any of these diseases if they'd vaccinate him!