The Watchtower also flip-flopped on Organ transplants. In 1961, they were acceptable but in 1967 the sect's leadership said it was cannibalism. In 1980,, the leaders erased this regulation.
The Bible has nothing to say about organ transplants and inoculations since they weren't invented until recently. Even so, we can imagine that the preservation of human life is something God cares about.
For instance, Joseph was sold into slavery in Egypt but he became part of God's process of preserving even pagan lives. He explained to his brothers in Genesis 45:5 (KJV), "Now therefore be not grieved, nor angry with yourselves, that ye sold me hither: for God did send me before you to preserve life."
But some might argue that extending life is equivalent to thwarting God's will. They might quote Deuteronomy 32:39 (KJV) which says, "See now that I, even I, am he, and there is no god with me: I kill, and I make alive; I wound, and I heal: neither is there any that can deliver out of my hand."
Jesus certainly never gave us any prohibition about seeing medical doctors. Mark 2:17 (KJV) reads, "When Jesus heard it, he saith unto them,' They that are whole have no need of the physician, but they that are sick: I came not to call the righteous, but sinners to repentance.'"
Jesus also healed ten lepers and told them to go see the priests so they could be declared clean. He wouldn't have done that had he forbidden us to see doctors. In those days, the priests doubled as health practitioners.
I'll be writing much more in my next book called You Think You're Going to Heaven? People need to know that our Lord is kind and wants to bless us in all ways.