It's similar (brand new) technology, so just like the Pfizer jab, we just don't know. We don't know the long term positive effects (they admit that will have to be seen in time), and we also don't know the long term negative effects. Which is why it's smart to wait... and probably why most anti-viral injections usually go through a 10+ year process! Which "vaccine" ends up being less harmful (and more effective) will be determined in the coming years.