Oh man, I wish I caught this thread earlier! I love debating vaccinations - mostly because 99% of people against it don't have a clue what they're talking about.
A few people covered it, but there is absolutely NO link between vaccinations and mental disorders like autism. (One botched study 30 years ago found a link; since then, every single follow-up has failed to find any interaction. One very recent study in Quebec found the rate of autism in their sample was higher in unvaccinated kids, which rather clinches the subject. Zero link. None.) There IS a link between vaccinations and allergic reactions causing death, but frankly the chances of such a reaction are lower than dying from the disease (regardless of what you're being vaccinated for) in the first place. All you have to realize is that there is always a risk factor in any medical intervention. The chances are low, but there is a chance that you can die after taking a single Tylenol. It's not cause-and-effect, it's interaction of a variety of factors. The same is true of vaccines. In millions of people, each with a slightly different immune system, there are always going to be an extremely low number of bad reactions, some of which may be fatal. Does that mean we should stop taking vaccines? Considering the implications of not being vaccinated, only an absolute fool would believe that. I'll demonstrate.
MMR is a common contentious vaccine because it doses for three diseases at once. (It is speculated that this may be why MMR has a slightly higher rate of bad reactions than other vaccines). For those who don't know, it stands for Measles, Mumps, and Rubella - all of which can be, and frequently were, lethal to children. Actually, they are capable of killing healthy adults too.
Polio is a debilitating illness that has been nearly wiped off the map which killed or crippled people for life. For people infected, the rate of complete recovery to normal was extremely low.
Smallpox killed millions every decade until a vaccine was developed that has led to it being officially declared eradicated. Survivors were scarred for life. The survival rate was also low.
Tetanus is a common bacterial infection that, without a vaccine, has no treatment. It WILL kill you - in excruciating agony as all the muscles of your body continue to contract until you suffocate because your lungs are doing nothing but contract. Again, eliminated with a vaccine administered every 10 years or so.
Whooping cough killed children all over the world prior to a vaccine being developed. I'll actually come back to this one.
Finally, we have the influenza virus - the single biggest killer of human beings in the history of the planet. The 1918 Spanish Flu pandemic killed somewhere between 50 and 100 million people globally before it petered out (and we still don't know exactly how many for sure). That's ONE outbreak. Double the number of people killed in the First World War.
What many of the anti-vaccination crowd forget is that the only reason prevalence of these diseases has gone down is because of "herd immunity" - vaccinate as many people as possible, and the disease is incapable of gaining a foothold. Every person who is not vaccinated is a disease carrier, at risk of developing and transmitting the illness. Usually, the implications of this where true herd immunity exists are low - the carrier is afflicted and recovers or dies without transmitting the illness, or after transmitting it to a very few people. However, when many people reject vaccination, the numbers of carriers and people vulnerable to disease goes up, and it can spread farther and faster. Think of it this way: In a class of 30 children, if 29 are vaccinated you have only one who can be infected. Therefore, the class itself is incapable of being a large scale vector. For each additional child unvaccinated, the number of vectors increases EXPONENTIALLY because of number of interactions outside the classroom can increase exponentially (depending how many people each child meets during the incubation phase of the illness). Once you have even 5 or 6 kids out of 30 unvaccinated, herd immunity no longer applies - the disease can travel between those 5 or 6 and to all the people they interact with who also lack the vaccination - and since the anti-vaccine sentiment runs in families and friendship groups, that becomes a very large number of people.
I have a great real-world example from whooping cough. Actually, two. The first happened in Japan in 1975. Following a vaccine batch that had several problems, two infants died in japan and several papers were published internationally about the pertussis vaccine in the mid-1970s. Japan eliminated the vaccine. With five years, Japan's rate of infection went from LESS THAN ONE per hundred thousand population, to over 11. Tenfold increase in the number of cases. By 1980, over forty children died per year and 13,000 were infected each year. Prior to the elimination, the infection numbers were around 1000, and there were 0-1 deaths per year. All of this because two children, out of millions vaccinated, died.
The second example is actually from Canada, in a town of less than a thousand people about 2 hours from where I grew up. The community is largely populated by 60s-era Vietnam draft-dodgers from the United States and other localized "hippie" communes. Three years ago, this tiny community experience FORTY-FIVE cases of whooping cough in a three week period. Why? Parents relied on herd immunity, and refused to vaccinate their kids. Unfortunately, the vast majority of the community followed this pattern. As a result, most of the children were unvaccinated, and B. pertussis spread throughout the community like wildfire. It was actually quarantined for some time as a result.
The risk of becoming seriously ill or dying from vaccination is incredibly low - literally off the scale. It is simply not worth opting out - for the health of the individual AND the group.
