I don't want to disparage nurses in any way because their work is absolutely vital and underappreciated but you don't really have to be an expert in the scientific method to be a nurse. You don't need to be able to describe how a chemical kills bacteria as long as you can properly sanitize equipment. You don't need to memorize all the components of blood to draw a blood sample correctly. And so on. There are a lot of nursing schools that are "career" focused where the goal is to basically give you the clinical skills you need to get a job as fast as possible and send you straight into the profession. Someone who graduates from one of those programs might not be any more knowledgeable about the immunology behind vaccines or the methods used to research their safety and efficacy than an average person. And that's totally fine as long as they're are willing to admit they're not an expert and follow accepted medical procedures whether they understand them or not. For some reason vaccines are an area where lots of people think their personal opinion is just as valid as the consensus among researchers so here we are.