What is the ruling on refusing to take the COVID vaccine without a medical excuse, and is that considered self-destruction and a sin, or is it a matter of divine decree and destiny?

Refusing vaccination is not considered suicide or self-slaughter, and a Muslim is not inherently sinful for opting out. However, its obligation may become preponderant if there is a general need, it is proven to cause harm to others, vaccines are available and safe, and the ruler mandates it.