Vaccine... Help? Deprogramming? Something?

You could start by writing the exact argument(s) by your relative. How can we respond to a claim we never heard? (Or did you just want very general pro-vaccination statements? I am sure google can help with this.)

Most vaccines are made without (or can be made without) thimerosal. In addition, thimerosal is safe.

https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/thimerosal-and-vaccines

Instead of reacting to individual comments, I'll try to summarize my thoughts here. Starting with disclosure: I have zero medical education, but I have two kids who are vaccinated, and my wife (a biochemist, used to search things in medical papers) did some research about it, and we talked about it; though there is a chance I may be misinterpreting what she told me.

For all practical purposes, if you are an average person, just get vaccinated. The research will cost you time and energy, and there is 99%+ chance your conclusion will be "get vaccinated" anyway. The rest of this comment is only useful if you are interested in truth and clear thinking per se.

First, remember the virtue of narrowness [LW · GW]. More can be said about one specific vaccine, than about vaccines in general. For example, if you want to know whether vaccine X contains thimerosal, try finding the composition of the vaccine X (assuming optimistically that it is a publicly available knowledge) rather than talking about "thimerosal" or "vaccines" in general. Consider the possibility that there may be multiple diferent recipes for the vaccine X; in such case, find out which one is relevant for you.

Second, quantities matter. It's not just whether "aluminum is bad", but also how much aluminum are we talking about. To give an example from a different area, we probably agree that radiation is bad for health. But you get some dose of radiation by simply walking outside for an hour during a sunny day. So if something gives you radiation that is, say, 1% of the one hour walking outside, you can probably ignore it; although on paper it will look scary. (On the other hand, I don't consider comparison between "aluminum in food" with "aluminum injected in the body" completely fair. You'd have to find a coefficient how much of the aluminum in the food actually gets into the blood stream.)

Third, there is a difference between the ideal case, and the real case. If a study tells you the side effects of a vaccine, you should expect that in real life they are probably going to be greater. Unlike the scientists carefully performing the study, some bored person in the production will sometimes get the dosage wrong, cook the viruses for 5 minutes instead of 15, forget to turn on the fridge, administer an expired vaccine rather than throwing it out, etc. On the other hand, the same is true about any other medicine or food, so it probably does not make vaccines more dangerous than the other things.

Now we get to the utilitarian calculus. The vaccines have some negative side effects (to say the very least, they hurt). But the diseases also have some negative side effects, and if you crunch the numbers, it turns out that it is better to vaccinate everyone than to have a fraction of your unvaccinated population die, or something like that.

Okay, the virtue of narrowness again: is this true for all vaccines, or only about vaccination in general? Good luck; getting all the data will take you a lot of time! You must explore each disease separately. What is the chance your unvaccinated child would get sick? (Is this a counterfactual world where no one is vaccinated, or where only your child is free-riding on the herd immunity?) Some diseases are unlikely to get to you, if most people around you are vaccinated. Other diseases will likely get to you anyway. What are the consequences? What is the second best treatment for the unvaccinated person?

The tricky thing is that these numbers change all the time. The prevalence of diseases gradually decreases with increased hygiene and vaccination, then suddenly increases with a wave of immigration, possibly depends on weather, etc. The alternative treatments evolve. The vaccines evolve, too, to have fewer side effects. In other words, the result calculated ten years ago may be different today, in either direction. This is mostly relevant when the result calculated ten years ago was relatively close to zero.

Notice that there are differences between countries: a vaccination mandatory in country A may be optional in country B and virtually unused in country C. Find out why. Sometimes it is caused by different situation (e.g. climate, disease prevalence) in different countries. Sometimes just different high-status experts have different opinions for bad reasons. It is quite possible that citizens of countries A and B living next to border close to each other have more similar environments than citizens living on the opposite sides of the country A; although the former will have different sets of mandatory vaccines, and the latter will have the same.

One more annoying complication: vaccines are usually not administered individually, but in batches. If there are 30 vaccines (number totally made up), instead of 30 individual shots you will get e.g. 3 shots containing 10 vaccines each. So even if it turns out that of the 10 vaccines in the same shot, 9 are necessary but 1 is useless, it may be more practical to just accept the standard batch, instead of trying to get each of those 9 necessary vaccines separately. (Maybe they are no longer produced and sold separately.) Yeah, this sucks.

...and as I said, after you spend 1 year researching all this, you will likely get to conclusion that you should simply get the stardard set of vaccines, because most of them are useful, instead of expending money and time (and taking your child to doctor 9 times instead of once) just to get rid of the useless ones that do not make significant harm anyway.

I second the recommendation to ask specific questions at Stack Exchange. (I would vote against RationalWiki though, because that site is more about winning debates and making fun of political opponents, than about getting things completely right.)

Vaccines sometimes kill people. Several serious diseases that killed many more people, we're told, are a much smaller risk now. At some point, you'd think people would want to selfishly avoid vaccinating so much. And that's what we see happening. There's a lot of rationalization going on.

Given the plenty of debate, out there right now, on this very subject — I don't think it very wise to start laying out claims here left and right. Especially those about your relative (who cares about those, right?) I recommend you a particular article, about how to deal which such stuff:

The Control Group Is Out Of Control [? · GW]

Bayesian statistics, alone among these first eight, ought to be able to help with this problem. After all, a good Bayesian should be able to say “Well, I got some impressive results, but my prior for [parapsychology] is very low, so this raises my belief in [parapsychology] slightly, but raises my belief that the experiments were confounded a lot.”

You don't have to become an anti-vaxxer just by hearing about some convincing evidence (which may be right or not) but instead become a bit more skeptic on the subject, that is, until you become better informed. That is, also, until you can better differentiate anecdotal and scientific evidence. If we cannot take this into consideration, and if things have to be either white or black, then, we are in for a very wild ride.

Epistemic learned helplessness might be worth reading. SSC has a post for everything.

The specific points your relative is making are very tired old anti-vaxxer arguments, not even interesting. I would guess that the confusion stems from this person being a true believer arguing with passion and convincing you. It is pretty simple, you don't need to win this argument with them. Trust the entire scientific community and your intellectual role models and move on. You are not going to win here. For each specific point you chase down the truth to, they will throw three more out when to talk to them again and if they can't think of any more, they will cycle back to points already covered. Or move on to talking about chemtrails. Of course if this issue interests you for its own sake, well

Thimerosal - Phased out of vaccines (except seasonal flu) around 2001, contained ethylmercury which is not a neurotoxins like methylmercury https://rationalwiki.org/wiki/Thiomersal

Aluminum - Extremely common element present in almost all our food, the dosage in a vaccine is comparatively tiny. https://www.mcgill.ca/oss/article/health/should-we-worry-about-metals-vaccines

How about a nice article from 2008 at science based medicine. https://sciencebasedmedicine.org/toxic-myths-about-vaccines/

Is the vaccination schedule to quick? Hmm... science based medicine again. https://sciencebasedmedicine.org/too-many-too-soon-no/

Vaccine requirements to attend public school is an affront to freedom? The irrational choices of anti-vaxxers can kill babies to young to get vaccinated, kill the immune compromised, spread disease in the general population. https://www.washingtonpost.com/outlook/2018/11/29/why-small-groups-vaccine-refusers-can-make-large-groups-people-sick/

As far as the nephew story goes, I assume you understand the value of anecdotal evidence.

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