The technology used to create the COVID-19 vaccines is too new to be safe.
The technology used, called messenger RNA (mRNA) is not new. Research on it began in the early 1990s, and two diseases that are very close to COVID — SARS (severe acute respiratory syndrome) in 2003, and MERS (Middle East respiratory syndrome) in 2012 — helped bring the mRNA vaccine development to present day use.
The reason this virus is technically called SARS-COV-2 is that there was a SARS-1, the original one, and scientists had already begun work on developing a vaccine for that virus. So, when this pandemic arrived, they had already developed a lot of the science. A decade of work had been in progress.