All the vaccines are targeting the spike protein. The mRNA vaccines are using mRNA that is degraded soon after it is translated into spike protein. So, there should not be any long term effects of the mRNA. The Astra Zeneca vaccine is using an adenovirus that is replication incompetent, meaning that the virus can’t live and grow in us. The Sanofi and NovaVax vaccines are protein vaccines, very similar to the flu vaccine. The end result is that while the technology is new, there is no evidence to indicate there is long term harm from the vaccine candidates.