To address the original question:
Lancet, a juried and the respected of respected medical journals, published a study, that suggested childhood vaccinations caused autism, something about mercury (miniscule amount) being part of the preservative and the cause of autism. The study was soon discredited and remains discredited.
This study was so bogus that a college freshman would have recognized it, yet it got published. Lancet had to retract it with huge amount of egg on it's face.
The 'scientist' had conducted the 'study' among children who attended his kid's birthday party. Several had been diagnosed with autism. He polled the parents whether their kids had been vaccinated. Based on the percentage that had been diagnosed with autism, his hypothesis, or conclusion, or whatever, was that vaccines could cause neurological disorders including autism.
Word of the 'study' findings went viral and many parents chose to not have their kids vaccinated.
When you have a disease come into a vaccinated, or otherwise protected (natural immunity) population, the disease won't take over in big numbers. When there is no immunity, it can take over. That is one reason for the panic over ebola in the US. We haven't been exposed over the years, no natural immunity, no vaccine.
Now, I was born in 1947, and as far as I know the MMR did not exist. All us kids of my age group got measles, mumps (painful!) and chicken pox. It was almost a passage, a part of growing up. We did get the smallpox vaccination and later polio vaccine. I got vaccinated for MMR when I went to nursing school as it was required.
These are just facts, not a political statement or position.