I did a little reading on this last night (like you said, information is always good!) It looks like MMR and chicken pox react differently, because they are made differently. I had absolutely no idea one could be contagious after the chicken pox vaccine, so thanks for sharing.
From the CDC's info sheet on chicken pox.
http://www.cdc.gov/vaccines/hcp/vis/vis-statements/varicella.html#risks
- Mild rash, up to a month after vaccination (1 person out of 25). It is possible for these people to infect other members of their household, but this is extremely rare."
The MMR vaccine, on the other hand, does not cause one to be contagious. There is nothing listed about the risk on the MMR fact sheet, unlike on the varicella one. More than that, there is lots of documentation that it's not transmitable via the vaccine:
From
http://www.nhs.uk/Conditions/vaccinations/Pages/mmr-questions-answers.aspx#contagious
"
If my child develops a mild case of measles after receiving their first MMR vaccine, are they contagious to non-vaccinated children?
No. Post-vaccination symptoms are not infectious, so your child will not pass anything on to non-vaccinated children.
http://www.cdc.gov/vaccines/vpd-vac/measles/faqs-dis-vac-risks.htm
"
I am 2 months pregnant. Is it safe for me to have my 15-month-old child vaccinated with the MMR vaccine?
Yes. Measles, mumps, and rubella vaccine viruses are not transmitted from the vaccinated person, so MMR does not pose a risk to a pregnant household member."
http://vec.chop.edu/service/vaccine...ne/mmr-measles-mumps-and-rubella-vaccine.html
"What are the side effects of the measles vaccine?
Some children develop soreness in the local area of the shot, and occasionally a low-grade fever. Reports have also indicated rare cases of fevers greater than 103 degrees, usually five to 12 days after receiving the shot. Also some children develop a mild, measles-like rash about seven to 12 days after getting the measles vaccine. Children with this reaction can still get the measles vaccine in the future. Children with measles rash from the vaccine are not contagious to other people."