You can check out part 1 and part 2 here. I will repeat my disclaimer: Please note that I am neither pro- nor anti- vaccine, but instead believe in researching and deciding what is best for that person in that situation. I feel that people should have the right to decline or choose any medical procedure or medicine, though I feel all such decisions should be undertaken after looking at all the pros and cons using reliable information. I am not a medical professional and would never presume to give medical advice; I am merely exploring the various reasons one might have for refusing some or all vaccines.
Religious reasons and adverse/allergic reactions are not the only reasons an educated person might choose to forgo vaccines. For some, it is a matter of examining the risk/benefit ratio and determining that, for them, the risk of the disease does not warrant vaccination. While some are criticised for coming to that conclusion when it comes to childhood vaccination, I'd wager that many have come to the same conclusion themselves for certain vaccines, such as the flu jab, even though influenza has the potential to be serious.
Some may point to studies showing that alternatives to certain vaccines provide as much as or more protection than the vaccine. For example, a breastfeeding mum, especially one who breastfeeds full-term, and whose child is generally well might choose to forgo the Hib vaccine for her child given that there is research showing that breastfeeding is quite effective at protecting against Hib. (side note: breastfeeding confers passive immunity from the mother, and so breastfeeding often helps a child have a less severe case of a disease; the significance with Hib is that the protective effect from breastfeeding continues after breastfeeding has stopped). She might choose to get the vaccine if the child seems prone to illness or if she simply decides she prefers the vaccine. I see nothing wrong with any of these informed decisions.
One may also decide that a particular illness isn't generally severe enough to warrant vaccination for that child. While varicella (chicken pox) and rubella can be severe in some cases, especially to a fetus if the mother contracts these diseases during pregnancy, these diseases are generally mild in children. That fact may lead some to skip those jabs altogether, or delay them until later if the child hasn't contracted the diseases by that time. This might especially be the case if the child is unlikely to encounter a non-immune pregnant woman early in her pregnancy, though others may feel this to be an unacceptable risk. Again, I have no problem with either decision and I fully recognise that the right medical decision for one family might not be the right medical decision for another, thus why I support researching and making the best decision for that person at that time.
A combination of these reasons might cause one to forgo the flu jab, either for himself or his child. While influenza can be miserable, most people recover from this seasonal annoyance without a problem. One who is otherwise healthy might therefore decide that the flu jab isn't indicated, and this may also go for a child, especially a breastfed child (I know from my experience that Kieran contracted a much milder case of influenza when we both caught it while he was still breastfeeding). Knowing that vitamin D supplementation bolsters immunity against influenza might help influence this decision.
Finally, some may simply feel that certain vaccines aren't necessary because the diseases aren't likely to affect them/their children. For example, in the US the Hep B vaccine is routinely given to all infants shortly after birth, regardless of the likelihood of the child contracting this disease. In the UK, it is not routinely given, due to the fact that the child is unlikely to contract it unless the parents/carers have Hep B. I always find it interesting to compare the vaccination schedules of different countries, seeing what is considered routine in one country versus another. Of course, one should also look at the circumstances in the different countries to assess why they might differ, as some diseases are more prevalent in some countries than in others.
These are just some of the reasons a person might choose not to vaccinate: reasons that are not often included when those who forgo vaccines are criticised. I should note here, too, that vaccine refusers do not seem to be at fault for the current pertussis outbreak. I respect the rights of the individuals to make their own medical decisions, or the medical decisions for their minor children, in this and every other medical area, and I encourage everyone to research whatever decision and choose what is best in your situation. It can be daunting looking through studies and evaluating them, but I like doing so just so I know what information is there.