Nephilim in the days of Noah were not human and therefore were unredeemable. Nephilim were half human, half demon and that is how YHVH will regard those who take an mRNA vaccine.
Demons are evil, twisted beings—so nothing they do should surprise us. As to a distinct motivation, one speculation is that the demons were attempting to pollute the human bloodline in order to prevent the coming of the Messiah. God had promised that the Messiah would one day crush the head of the serpent, Satan (Genesis 3:15). The demons in Genesis 6 were possibly attempting to prevent the crushing of the serpent and make it impossible for a sinless “seed of the woman” to be born.
This dreary picture is echoed in the New Testament. Jesus said it will be a time of tribulation “such as has not occurred since the beginning of the world until now, nor ever shall” (Matthew 24:21). In fact, Jesus said it will be so terrible that if it were not stopped at the end of seven years, it would result in the destruction of all life (Matthew 24:22). The Apostle John states that the chaos will be so great that the leaders of the world will crawl into caves and cry out for the rocks of the mountains to fall upon them (Revelation 6:15-16).