From the article I linked above:


There is one other very important thing to note from the graphs. Anti-vaccination advocates often try to explain the dramatic decrease in vaccine-preventable diseases in terms of increased sanitation. They say that these disease rates are so low because we have developed better sanitary practices over the years. However, these graphs show that this is just not true. After all, the polio disease rates decreased dramatically in the late 1950s. However, the measles rates did not decrease dramatically for another 10 years. If good sanitary practices were responsible for the drop in disease rates, you should see the disease rates fall roughly at the same time. That’s just not the case. The disease rates fell only when vaccines were tested and then approved. Also, note the short time over which the disease rates fell so dramatically. Do sanitation practices change so quickly that they completely "clean up" a country in a matter of a few years? Definitely not! Improved sanitation just does not explain the data.

In fact, most medical historians blame increased sanitation for the rise in polio from 1944 to 1952. When sanitary practices were rather poor, people were regularly exposed to small amounts of the polio virus, usually when they were babies and therefore had the extra protection given to them by the antibodies they received through their mothers’ milk. Their immune systems were able to conquer the weak exposure to the virus with the help of their mothers’ antibodies, and thus they became immune. As a result, the poor sanitation was actually acting like a "dirty" vaccine! As sanitary practices improved, fewer people were exposed to small amounts of the virus as infants. As a result, when they were exposed to concentrated amounts of the virus (from a person who already had the disease, for example), they would succumb to the disease4. Note that this makes sense in the light of the data, because the rise in the polio rate occurred slowly, which is what you expect when sanitation is playing a role.

Although these graphs are very effective illustrations of the power of vaccines, as we stated before, they are not definitive evidence. After all, coincidences could explain the graphs. By far, the best evidence of how effective vaccines are comes from controlled studies. In these studies, vaccinated people are compared directly to unvaccinated people, and the results are astounding,

For example, Feikin and others studied all measles and pertussis cases among children (age 3-18) in Colorado from 1987 to 19885. When they compared the vaccinated children to the unvaccinated children, they found that vaccinated children were 22.2 times less likely to contract measles than were the unvaccinated children. In the same way, vaccinated children were 5.9 times less likely to contract pertussis than were unvaccinated children. In other words, according to this study, if you do not vaccinate your children, you have increased their risk of getting measles by 2,220%, and you have increased their risk of getting pertussis by 590%!

Another finding from this study is that schools in which outbreaks occur have 2.9 times the percentage of unvaccinated students as do schools in which outbreaks do not occur. Thus, this study tells us that those who do not vaccinate their children are not only putting their own children in danger, but they are also putting other people’s children in danger, because the larger the number of unvaccinated children in a group setting, the more likely an outbreak is to occur.

But face it, SJ; we're not going to convince them; they'll continue to put their children and other people at risk.
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If you vote for government, you have no right to complain about what government does.