Disneyland workers diagnosed with measles

[jeff47]

21. By having an allergic reaction to earlier vaccines

The first MMR vaccine comes after a lot of earlier vaccines.

If a child has an allergic reaction to earlier vaccines, they don't get the later ones. It's vaguely like being allergic to peanut butter or bee stings - their body's over-reaction to an antigen can cause swelling everywhere, which can block off their throat and they suffocate.

As a result, newborns are watched very closely when they get their first vaccinations - it's one of the reasons a baby stays overnight in a hospital after birth. The allergic reaction can be suppressed via drugs, or worst-case handled via intubation. So it can be handled if it happens while a baby is in a hospital, but that allergic reaction makes it too risky to give later vaccinations.