God, apparently.
There is also plenty of distrust. This is to be expected, given the well-known existence of lobbying by for-profit pharmaceutical companies that are legally protected from all liability. Specific complaints are that vaccines are manufactured using tissue cultures from aborted babies, that some of the diseases aren't even present in the USA (can vaccinate if they come back), that disease risks are overstated (given modern care and general health), that vaccine risks are understated (the window of time for a vaccine injury to be legally accepted is too narrow), and that pharmaceutical companies refuse to offer some of the vaccines in single-disease form.
For example, one of those combo vaccines (I think the MMR or DTAP) is a problem for somebody I know. A single component of the vaccine is made from tissue culture that originates from an aborted baby. The kids would be vaccinated for the other diseases if it were possible to get separate vaccinations in the USA. Japan has separate vaccinations available, but a trip to Japan is a major undertaking.
Some people are resistant to a hard sell. The supposed "education" to push for vaccination is always very one-sided. People can see it. The harder the push, the more suspicion is generated. It's sort of like the car dealer experience.
One point I'd make, about the "tissue culture that originates from an aborted baby" vaccine. According to [1], the MMR vaccine:
"The viruses are cultured in aborted fetal tissue cells. The cells were obtained more than 50 years ago, as a result of elective abortions"
There are no new fetal tissues being "harvested" (I know that's not the proper term, forgive me) to make more vaccines. They are keeping cultures donated fifty years ago growing.
I can understand people not liking the hard-sell on vaccines, but what I can't wrap my head around is how much effort should have to go into the argument "give your kids these shots so a horrific number of children don't make it to 15". The CDC has a broad info page, but one point comes across crystal clear to me (even specifically about the MMR vaccine):
"An epidemic of rubella (German measles) in 1964-65 infected 12½ million Americans, killed 2,000 babies, and caused 11,000 miscarriages. Since 2012, 15 cases of rubella were reported to CDC." [2]
1: https://www.verywellhealth.com/do-vaccines-contain-aborted-f... 2: https://www.cdc.gov/vaccines/vac-gen/whatifstop.htm