https://regenerativemc.com/biodistribution-of-pfizer-covid-19-vaccine/The bottom line is mRNA Covid vaccines are still considered experimental by the FDA as  research continues to be done.  We do not have all the animal or clinical data needed to completely evaluate long term safety of the mRNA vaccines.  We won’t know the final answers to many questions concerning the mRNA vaccines until at least 2022 or perhaps longer. People will continue to gather evidence supporting the vaccine, and people will continue to gather evidence against the vaccine.  Ultimately at this juncture, it is a personal decision considering the risk vs. benefit ratio.   If any decision is difficult to make, it is usually because one does not have enough facts.