Background: In order for systematic reviews to be useful to decision makers such as patients, clinicians, and policy makers they need to consider both the benefits and potential harms of any intervention. Including all harms in a systematic review can be challenging and is not the preferred method for most systematic reviewers. Selecting the most appropriate harms to search for, however, can also be problematic. One potential source of information for patient important harms is social media.
Objectives: To create a list of candidate harms from social media for inclusion in a Cochrane review on HPV vaccine.
Methods: We searched on WebMD and Twitter for HPV vaccine drug reviews or Tweets posted between 2007 and 2021. Each drug review from WebMD was manually annotated for mentions of any adverse events experienced by the person posting or someone they cared for. For each Tweet we used automation to extract mentions of adverse events and normalised them to MedDRA codes.
Results: Of the 133 reviews identified from WebMD, 124 reviews mentioned at least one adverse event experienced, with 343 mentioned in total. Our search on Twitter yielded 14,049 posts for adverse events experiences of which 10,271 the adverse event could be normalised to MedDRA preferred terms.
We could then identify a list of the most common adverse events experienced such as injection site pain, headache, menstruation disturbances, and fatigue. Those adverse events experienced by teenagers (such as injection site pain and syncope) differed to those feared by parents (paralysis and promotion of sexual activity). There was also considerable fear of infertility – which was often thought to follow on from menstruation disturbances.
Conclusion: Social media can be valuable in identifying potential harms that are experienced or feared by patients or caregivers. Social media data could be used alongside regulatory data, patient information sheets and input from clinicians and patient and public representatives to identify candidate harms for inclusion in Cochrane reviews.

Patient, public and/or healthcare consumer involvement: An Independent Advisory Group (IAG), including consumers, advised on overall review production and content, and responded to community concerns.