Table 2.

The major topics of misinformation identified by topic modeling (n=7207).

Misinformation topic	Prevalence, n (%)	Explanation	Examples (excerpts)
General vaccine adverse events	2672 (37.07)	Promotion of general misinformation regarding the safety of HPVa vaccine	“The HPV vaccine is unnecessary and unsafe.” “The HPV vaccination causes retardation.”
Conspiracy theory	1072 (14.87)	Propagation of conspiracy theories about HPV vaccine and fraud by the government and large pharmaceutical companies (eg, Merck)	“Rick Perry signed an executive order trying to mandate Gardasil vaccines for young girls. He did this to make money for his buddies at Merck.” “The HPV vaccine is a joke pressed on schools and administrations by greedy pharmaceutical corporations.”
Citing unfounded studies	989 (13.72)	This type of misinformation can be very misleading because it tends to cite and interpret scientific studies from sources that are not scientifically peer reviewed	“Flawed safety study on HPV vaccine triggers butterfly effect - leaked e-mails reveal who suppressed info on dangerous particles in vaccine” “We find that HPV vaccine clinical trials design, and data interpretation of both efficacy and safety outcomes, were largely inadequate”
Vaccine deaths and serious reactions	520 (7.21)	Propagation of HPV vaccine–induced death and serious adverse reactions	“For instance, the HPV vaccine has caused children to die.” “The shots have killed women. The adverse event reports from the FDAb about HPV vaccination read like a litany of horrors.”
Aluminum-containing adjuvants	456 (6.33)	Promoting misinformation on safety issues of aluminum-containing adjuvants in vaccines	“Another good keyword is for Gardasil adverse drug reactions. That’s how I found this: ‘each 0.5-ml dose of the vaccine contains approximately 225 mcg of aluminum (as amorphous aluminum hydroxyphosphate sulfate adjuvant)’ This study clearly shows that aluminum found in vaccines can cause neurologic damage.” “Brain damage and autoimmune diseases can be caused by aluminum adjuvants. Aluminum adjuvant is in the HPV vaccine.”
Vaccine and autism	198 (2.75)	Promoting misinformation on the discredited links between vaccine and autism	“The HPV vaccine causes autism” “Vaccine court awarded millions to two children with autism. CDCc report creates controversy for Merck’s Gardasil vaccine”

^aHPV: human papillomavirus.

^bFDA: Food and Drug Administration.

^cCDC: US Centers for Disease Control and Prevention.