The rate of serious adverse events like encephalitis for vaccines is rare, for instance the measles/mumps/rubella vaccine has documented encephalitis cases on the order of 1 in 1 million doses delivered. The measles sickness itself, if you get it can cause encephalitis on the order of 1 in 1000 confirmed measles infections, and 2.5 deaths per 1000 confirmed infections.
In Canada, the peak number of measles cases occurred during the period 1950-1954, at roughly 61,000 cases a year. So it wouldn't have been unusual to have 61 cases of encephalitis, and anywhere from 122 to 183 deaths in a year like that. This at a time when the population in Canada was less than half of what it is now. So let's double the number of cases assuming the prevalence wouldn't have changed-which is actually pretty dubious considering Canada has become much more urbanized in the past 60 years.
In 2009, 92% of two year olds had been vaccinated. The CANSIM tables from Stats Canada don't get that fine with their buckets, but there are about 2 million 5 years olds for that period. So, 2 cases of encephalitis in one year would not be unusual.
120 cases of brain swelling and possibly 360 deaths could be occurring today without vaccines. Two children will have brain swelling from the vaccine.
To not even mention anything about how much worse the antibiotic resistance problem would be if we were still relying on antibiotics instead of preventing disease.
The story is very much similar for other preventable diseases. Context. It matters.