What adverse events can be expected following HPV vaccine?

In clinical trials of 9vHPV (Gardasil 9, Merck) involving more than 15,000 vaccine recipients, most adverse events were mild or moderate injection site-related pain, swelling, and redness. Up to 40% reported one of these injection site reactions after vaccination, and they were more common among females compared to males. Injection site reactions also were more likely following the second or third dose compared to the first dose. Fewer than 10% of recipients reported fever.