You can certainly refuse to do anything but this carries a lot of risk and a lawsuit would be daunting and expensive. If you're wanting to commit to that, by all means. The middle ground is the religious exemption. This does not need to be religious per se but an ethical or moral belief had with a similar regard to typically religious ones. You're best following their forms and jumping through their hoops, however, to the least extent reasonable. Theoretically, a statement just saying, "I have a religious exemption to this mandate" should be enough but a good rule of thumb for anything like this is to think of it as if a judge is already reading it... would adding 1 or 2 sentences endear your position to a reasonable person without boxing you in very much philsophically? It might be better to do that then. The prolife argument is a good one as the available shots were either developed with embryonic cells and/or contain them. However consider that other shots may become available for which this argument may not be valid. Consider any oaths/pledges/etc that you have sworn and if they might be relevant to your situation. Citing those might be sufficient, perhaps augmenting them with a Christian perspective, "let your yes be yes and your no be no". If you took vaccines before, it is OK that your beliefs have changed, that is valid, just be sure not to offer conflicting statements here(or in any of your paperwork). Don't say that you just don't trust this one but you did the others... They will likely open a dialog with you, they should not challenge/argue your beliefs but they may work to create situations where you contradict yourself in person or in writing... be vigilant not to step into these traps. They still can fire you if your belief creates more than a minor cost to the company, understand that. There's a difference between denying your religious exemption and not being able to reasonably accommodate your beliefs. Good luck