Researchers aimed to review scientific findings regarding reported adverse side effects of the four available COVID-19 vaccines. Currently, two mRNA vaccines and two DNA vaccines have been authorized for use by international agencies. Though the vaccines have led to a reduction in COVID-19 infections and death, some adverse events have been reported. Cases of thrombosis have been reported in various case series studies for both DNA and mRNA vaccines. Investigators of these studies have found high levels of a specific antibody that leads to thrombosis following DNA vaccines. This finding resulted in the study authors defining this as a new syndrome called “vaccine-induced immune thrombotic thrombocytopenia (VITT). Other studies report no causal link for DNA vaccines and thrombosis, but investigators state they cannot exclude it as a possible side effect. Cases of thrombosis in those who recently received a Ad26.COV2.S vaccine (a DNA vaccine) have even halted administration of the vaccine in the US. Another reported adverse event are hypersensitivity reactions. Though some anaphylactic reactions were reported, delayed hypersensitivity reactions appear to be more common. Authors report that the advantages of COVID-19 vaccines outweigh the possible rare adverse events, but the safety and tolerance of the vaccines must continue to be studied.