Participants were observed for 30 min after vaccination, to assess the occurrence of any immediate unsolicited systemic adverse events (AEs). Information on solicited injection site (pain, erythema, swelling) and systemic (fever, headache, malaise, myalgia) reactions was collected for 7 days after vaccination in diary cards and were considered vaccine related. Participants were also asked to record information relating to any unsolicited AE from Day 0 to Day 30 (window, +14 days) in their diary cards, including the occurrence, nature, time to onset, duration, intensity, action taken, relationship to vaccination, and whether it led to early study discontinuation/termination. The same information was collected by the investigator for any serious AEs (SAEs) and AEs of special interest (generalized seizures, Guillain-Barré syndrome, and idiopathic thrombocytopenic purpura) reported up to 30  (window, +14) days post-vaccination, along with information on seriousness criteria (collected in lieu of intensity) and outcome.