1. you presume someone unvaccinated has the measles with no basis for that presumption
2. you shed the virus after having the vaccination
3. herd immunity is the bullshit they sell to get people to vaccinate. adults who were vaccinated as children don't get the boosters.

So what's in the vaccine?

potassium chloride - Until 2009, most states used a three-drug combination for lethal injections: an anesthetic (usually sodium thiopental, until pentobarbital was introduced at the end of 2010), pancuronium bromide (a paralytic agent, also called Pavulon), and potassium chloride (stops the heart and causes death). https://deathpenaltyinfo.org/state-lethal-injection

urea - a soluble weakly basic nitrogenous compound CO(NH2)2 that is the chief solid component of mammalian urine and an end product of protein decomposition, is synthesized from carbon dioxide and ammonia, and is used especially in synthesis (as of resins and plastics) and in fertilizers and animal rations https://www.merriam-webster.com/dictionary/urea

monosodium L-glutamate (MSG)- Monosodium glutamate (MSG) is a flavor enhancer commonly added to Chinese food, canned vegetables, soups and processed meats. The Food and Drug Administration (FDA) has classified MSG as a food ingredient that's "generally recognized as safe," but its use remains controversial. For this reason, when MSG is added to food, the FDA requires that it be listed on the label. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/monosodium-glutamate/faq-20058196

aborted human fetal cells - does this really need a definition?

bovine serum - Bovine serum is a by-product of the meat industry. Bovine blood may be taken at the time of slaughter, from adult cattle, calves, very young calves or (when cows that are slaughtered are subsequently found to be pregnant) from bovine fetuses. http://vaccines.procon.org/view.resource.php?resourceID=005206#bovine

Meat industry byproduct, hmmm. CAFO is a commonly used acronym for concentrated animal feeding operation. http://www.sierraclub.org/michigan/why-are-cafos-bad E. coli 0157:H7 - Cattle are reservoirs for Shiga toxin producing E. coli bacteria. E. coli 0157:H7 strains do not make cattle sick because their bodies do not have receptors like humans do for the toxin to attach and replicate. Meat typically becomes contaminated with E. coli during the slaughtering process http://sphweb.bumc.bu.edu/otlt/mph-modules/ph/livestockproduction/LivestockProduction6.html

These are just a few of the ingredients in the Merck vaccine. I think I'll take my chances with the measles, oh wait, I already had the measles as a child, and miracle of miracles, I SURVIVED.