Q: Are vaccines 100% safe?
A: No. Many many high quality studies have been done, and vaccines have been shown to cause side effects in very rare situations. Most of the side effects are mild.
Q: Have any of those studies shown a link between vaccination and autism?
A: No. Despite extensive research and thousands of subjects, no link between vaccine and autism has ever been demonstrated. And given the persistent inability to demonstrate such a link, it is very unlikely that such a link exists.
Q: But what about that original paper that proved that vaccines caused autism?
A: The original paper was a fraud, plain and simple, done for material gain. The paper was eventually retracted and the author was stripped of his medical license. Numerous subsequent studies, with far more rigorous methods and greater number of enrolled patients, failed to demonstrate any link.
Q: But what about all of those stories of children who were vaccinated and their behavior seemed to change irrevocably overnight?
A: In a nutshell, those kind of stories are called "anecdotal evidence", which means we hear a story and are left to wonder how accurate the story is and also whether any real conclusions can be drawn from it. The multiple rigorous studies done are of much more superior quality, and failed to demonstrate any link.
Unfortunately, symptoms of autism and vaccinations both occur early in a child's life, and when a child begins to exhibit certain behavioral symptoms, it can be tempting to link it in time with another occurrence, with a cause, to try to explain it. If the anecdotal evidence was indeed reflecting a cause and effect between vaccines and autism, the dozens of rigorous studies with thousands of patients would presumably have uncovered it.
Q: But everyone knows that the "rigorous studies" are run by people who are financially motivated by the vaccination companies to come to certain conclusions! Maybe that's why they haven't found anything, whereas the anecdotal evidence and lay publications are free of such ulterior motives?
A: As long as humans are involved, one can always suspect that they are motivated by ulterior motives, that is true. However, ulterior motives are to be found on both sides of the aisle, and there is a double standard in suspecting the pro-vaccine camp of altering the truth for ulterior motives, while accepting as pure truth every word from the anti-vaccine camp. An equal standard and ratio of acceptance/suspicion should be applied to both sides.
Q: Fair enough, but if that's the case, how do we know anything is true? Who are we to trust?
A: As the saying goes, "Democracy is a terrible way to govern, but it's the best we've got". Statistics and mathematics are the best tools we have to find out the real truth of the matter, despite errors that can creep in. When it comes to using statistics to uncover that truth, there are better ways and worse ways of going about it. In other words, there are ways that are more susceptible to error, either intentional or inadvertent, and ways that are less susceptible.
The strongest available methods out there have time and again failed to demonstrate any link between vaccines and autism. You may be skeptical and say that those stronger methods were susceptible to ulterior motives, but then you have to equally apply that skepticism to weaker statistical methods, if not more so. Then when the dust settles and your blanket skepticism on both sides cancels itself out, you're left with all the strong methods of research failing to show any link at all.
Q: But what about all the toxins in vaccines? Mercury? Aluminum? Etc? That can't be good for my baby, can it?
A: First of all, the idea of "scary toxins" that are bad because they sound bad is a made up concept. Each item has be examined for itself. If I told you I would feed your child a food containing copper, manganese, and zinc, would that scare you? But Cheerios contains those minerals, and more. The copper in the Cheerios is not dangerous of course, although anyone would agree that eating inordinate amounts of copper can be dangerous and can cause copper toxicity.
It is similar for the concern of mercury in vaccines. While of course mercury toxicity is a thing, that should no more scare you away from vaccines than copper toxicity should scare you from eating Cheerios. Mercury exists/existed in some vaccines in the form of ethylmercury, a breakdown product of thimerosal. Ethylmercury is easily eliminated from the body and has never been shown to cause any harm at the levels it exists in vaccines. (Mercury in fish exists as methylmercury, which is not as easily eliminated from the body.)
To top this all off, thimerosal has never been a component of MMR vaccines, the vaccines eyed with the most suspicion. In fact, currently there are no childhood vaccines that even contain thimerosal, and almost all pediatric vaccines, including MMR, are completely preservative-free.
Aluminum is used in some childhood vaccines to boost the immune response to the vaccine. They are used in very low doses, and have overall been demonstrated to be safe over multiple decades of use.
Q: Still, why do we have to give so many vaccines all at once? Intuitively that seems to overwhelm the body - wouldn't it be better to space the vaccines out a bit more?
A: Insofar as vaccines have never been demonstrated to cause autism or other such effects, it's hard to argue that spacing them out is even less likely to cause autism. As to whether we should space them out "just to be safe" - how soon do you put your seatbelt on in the car?
Q: But do we really even need vaccines? Have they really been effective?
A: YES. YES. When looking at the deaths from various diseases before the vaccine was introduced and after the vaccine was introduced, there is a staggering difference in the mortality rates; often a difference in thousands of deaths per year! You'll be hard pressed to find any other medical intervention even approaching that degree of success. And if you claim that the data that demonstrates this is rigged, I refer you to your double standard above.
Q: Even if what you say is true, what if I'm still scared and don't want to vaccinate my child? Shouldn't that be my choice?
A: First of all, even if you are entitled to make the choice to not vaccinate your own child, you would be contributing to weakening the "herd immunity". That means that if below a certain percentage of people in a group are not vaccinated, the infection now has a way of jumping from person to person.
Think of it as stepping stones scattered in a stream; each child vaccinated gets rid of a stepping stone; if enough stones are eliminated, the infection will be stopped in it's tracks and can no longer hop it's way around the stream. However, if enough children are not vaccinated, then there will be enough stepping stones left to allow the infection to make it's way around the stream.
This can be devastating for children who have weak immune systems, such as children fighting cancer, who cannot get vaccinated themselves. Whereas before these children were safe because the infection didn't have a way to hop over to them, now that herd immunity has been weakened to a certain point, the infection can Gd forbid reach them.
Second of all, do you really have the ethical right to make decisions for your child that according to all available data can harm your child? To take an extreme example, if a child does Gd forbid contract meningitis, does a parent really have the right to refuse antibiotic therapy out of concern for "toxins" in the antibiotics? To be sure, even if you don't vaccinate your child they may be protected by herd immunity, but with enough similar minded parents, herd immunity may be considerably weakened. Furthermore, Gd forbid none of us know if for whatever reason our child will develop a weakened immune system for whatever reason.
Q: If vaccines have really been so effective, why do we not see their use encouraged in the Jewish world?
A: Their use has been encouraged, and borderline mandated, by Jewish leaders; both when vaccines first came out, and by contemporary poskim. See the powerpoint here. In addition, the Rebbe has written many letters encouraging their use, as can be found in that powerpoint.
Q: But maybe all of the positive attention and encouragement for vaccines was when the vaccinations were against the really dangerous diseases; some of the vaccines today vaccinate against diseases that are not as deadly as the original vaccinations?
A: To be sure, the initial vaccines were focusing on reducing the "low hanging fruit", the really nasty diseases; as those were dealt with, vaccination development turned to the not-so-low hanging fruit, to reduce illness or death to whatever extent possible. Although the mortality reduction isn't as dramatic, the fundamental argument of the safety of all vaccines and their benefit nonetheless remains the same.