It seems like your argument is [value of vaccine] = [reduction in death] - [unknown long term risks of vaccine]
And if you're risk of death is low enough that swamps the third term. But I think you're modeling this incorrectly. It's actually [value of vaccine] = [reduction in death] - [unknown long term risks of vaccine] + [unknown long term risks of novel virus]
And this case it almost always makes sense to take the vaccine.