Table 3.

Categories of concern-related tweets around HPV vaccine

Type of concern	Definition and example tweet	Number of tweets (%) * N = 931
Health	Vaccine is not safe: health related adverse side effects/ serious reactions Example: “the gardasil/hpv vaccine destroyed our lives. #gardasillkilledmyson”	539 (58)
Mandatory	Forced vaccination, violation of parental rights Example: “this is a person who wants to mandate medical procedures for your 9 year old without your consent. #gardasisdangerous #parentscalltheshots”	180 (19)
Ineffective	Vaccine does not prevent hpv-associated cancer or hpv infection Example: “#hpv vaccination is not reducing #cervicalcancer rates. To the contrary research shows that it is making matters worse.”	127 (14)
Other safety	Inadequate or falsified safety monitoring “merck’s own #study: #gardasil increases cervical lesions in women by 44%”	106 (11)
Government	Government or group conspiracy, or money-making/profit incentive “governor announced significant investment by merck in the county. #gardasil”	69 (8)
Big pharma	Deception or money-making incentive on part of pharmaceutical companies Example: “when you blindly follow the system, thinking that bigpharma has your best interests, you might just ruin the future of your children. #gardasilkills”	65 (8)
Vague/general	Nonspecific concern (not covered by one of the other categories) “professor condemns #hpvvaccine after winning $270 k federal grant to study it.”	64 (8)
Other	Other specific concern “parents, it is imperative you research everything a doctor/nurse tells you when it comes to #hpv vaccine. Doctors are paid a bonus for every shot they give. It’s the bread and butter of a practice!”	40 (5)
Concerns in the literature	Child too young, child not sexually active, no provider recommendation, poster needs more information, not required by school	16 (2)

*Categories were not mutually exclusive. Tweets could be assigned to multiple categories. Percent not equal to 100