Jan 27 2015
This is an ongoing story that isn’t over yet. As it has been raging for days now, most people have probably heard that there is a big measles outbreak starting in Disneyland in California. There are now 87 confirmed cases of measles, 50 of which can be directly linked to Disneyland. Of the 42 people so far whose vaccination status is known, 34 were unvaccinated, 3 were partially vaccinated, and 5 were fully vaccinated.
Yes, this is caused by those who are not vaccinated
One thing is absolutely certain from these numbers – this outbreak has largely been caused by those who are not vaccinated. As you can see, most of those affected are unvaccinated. The vaccination rate for MMR is about 90% in the US. This means those who are unvaccinated were about 67 times more likely to be infected with measles in this outbreak than those fully vaccinated.
If vaccination rates were higher, then herd immunity could have stopped or severely limited the spread of the disease. That is the point of herd immunity – if enough people are protected then the virus is less likely to find a vulnerable host and continue the spread. The vaccine is about 97% effective in those fully vaccinated, which is why there were a few vaccinated people who contracted the disease.