It's because there are two topics--both deep and nuanced--that neither side is eager to discuss.
Suppose that in a class of 30 children, 29 are vaccinated against measles. The one who isn't vaccinated will never get measles--who would he catch it from?
Now suppose there is a small risk of severe reactions to the measles vaccine. Every parent in in that school will want his own child to be the one child who is not vaccinated. It's natural for us to want every possible protection for our children. "Let my child get 100% of the benefit from the immunity, while carrying none of the risk."
So the authorities don't want to discuss the one-in-thirty phenomenon. The topic is a hot button that could tear apart the community, pitting each parent against the others, and all against the school authority.
This is a problem that has no equitable solution. There is an essential conflict between individual freedom and public health. So instead of allowing a discussion--which can only be heated and inconclusive--we will ridicule anyone who raises questions about vaccines. We will shame him and call him superstitious and anti-scientific. If he is a doctor, we will revoke his license to practice medicine , take away his livelihood, then drive him into debt with a lawsuit.
The technical name for this behavior is "dirty pool". The predictable result is that, on the other side, you have victims who are hit when they're down. You have Andrew Wakefield who gave his time and expertise in a great public service, screaming that the system is corrupt and can't be trusted. You have thousands of parents who are devasted by the condition of their children, trying to cope with the multi-faced challenges of raising a disabled child, being told to shut up and sit down when they try to warn others that vaccines might be a factor in their child's condition.
The truth is that there are many factors contributing to a much higher autism rate in the present than in the past. There are many grieving parents of struggling, suffering children. Children who have received the MMR vaccine are at higher risk for autism. Perhaps the best evidence for this is the number and prominence of reports eager to deny the connection [link, link, link, link, link, link, link, link, link, link]. But for any individual child, it may be impossible to know whether the vaccine was responsible for his condition.
Our communities may, in some cases but not others, be justified in requiring vaccinations as a condition for children to receive hospital benefits and enroll in school. The argument depends on details of the risk rates for adverse reactions, the severity of the disease, the statistics about herd immunity, and the long-term health consequences both for the individual and the community. (For example, protecting kids from measles seems like a no-brainer until you see a study finding that kids who don't get measles grow into adults who have higher risk for cancer .) Even when all these factors are known and considered, there will be disagreement between those whose philosophy leans toward liberties for the individual or toward the primacy of social benefits.
Many vaccines are manufactured by a single supplier, and the government is requiring every person to purchase the product. This is hardly a situation where we can rely on the "free market" to insure equity. It gets worse. Each company is responsible for testing the safety of its own product, while the same company is allowed to profit enormously if it finds that its product is safe, but loses money if the finding is that the product is unsafe. Scientists may be basically honest, but what do you think happens to scientists when you put them in a position where such a huge financial interest to their own employer hangs on their finding yea or nay?
There's one more benny that assures the vaccine manufacturers a sweet deal. Congress in its infinite wisdom has passed a law transferring all legal liability for injuries sustained by vaccine patients from the pharmaceutical company to the US taxpayer. I can't prove that this has anything to do with the pharmaceutical industry being the largest lobbying army in Washington , but it's an interesting correlation.
If you have a bad reaction to a vaccine, you can't sue the vaccine manufacturer, but you can sue the National Vaccine Injury Compensation Program, and if you win, you will be compensated by the US Dept of Health and Human Services. As of 2017, the program had been found liable in about 4,000 lawsuits, and paid an average of $1 million per claim. Almost a third of those claims were for death of a loved one attributed to vaccine. The Vaccine Adverse Effects Reporting System (VAERS ) receives about 30,000 reports each year. (It is more difficult to know how many adverse reactions go unreported, how many claims go unfiled, and how many smaller injuries have not been serious enough to pay for a lawyer's time.)
Separating the profit from the liability is a terrible idea, and invites corruption. Permitting a monopoly to operate in an area where customers are a captive audience is manifestly unfair, and the Federal government's refusal to regulate the monopoly almost assures abuse.
No wonder it's so hard to tell which vaccines are safe and effective, and which are worse than useless. The industry has stepped into this information vacuum with the world's largest, most expensive, and most sophisticated PR program shouting about public health benefits while suppressing the costs and complications. An army of social media trolls makes sure the debate remains lopsided.