Because of the psychological power of rhetoric, words do matter. As philosophers point out in critical thinking, words have both a denotation (the meaning) and a connotation (the emotions and associations invoked). Words that have the same (or similar) denotation can have very different connotations. For example, “police officer” and “pig” (as slang) have the same denotation but rather different connotations. As would be expected, the fight over vaccines involves rhetoric. One interesting example is that presented by Ben Irvine: “People who don’t want the vaccine aren’t “refusing” it. You don’t say a person is “refusing” to take anti-depressants. Or “refusing” to get married. You can decline without refusing. You decide what’s best for you. Refuse is a manipulative term, loaded with unfair moral pressure.”
As Irvine indicates, while “refuse” and “decline” have similar meanings, they differ in their rhetorical loading. As Irvine sees it, “refuse” is negatively loaded with “unfair moral pressure.” Presumably “decline” lacks this quality.  So, what is the difference between the two words?
In a moral context, “refuse” implies rejecting something actively and with some degree of force. There also often seems to be an implication of expectation that one would accept rather than reject.  Interestingly, the context determines whether the connotation is negative or positive. As would be expected, if what is being refused is seem as morally wrong, then using “refusal” would often suggest something positive. For example, “Sergeant Jane Doe refused to obey an illegal order.” This would suggest something positive, that Doe actively rejected the order and that there is an expectation that soldiers will obey orders. Interestingly, people who believe that requiring COVID vaccinations is morally wrong should embrace the language of refusal—to refuse something wrong is the right thing to do. But “refuse” can also be negative.
As Irvine notes, to say that people who decide not to get. . .