Table 2. Data Sources and Topics [Note that ethics-related papers are excluded from this table as they are frequently concerned with social media in general.].

Data Source	Vac a	Comm b	Cancer	SA c	Pharmaco d	STI e	MH f
Reddit	-	10	-	11 12 13	-	14	15 16 17 18 19 20 21 22 23 24 25 26 27
Twitter	28 29 30	31 32 33	34	6 , 12 , 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49	50 51 52 53 54 55 56	57	18 , 58 59 60 61 62 63 64 65
Instagram	-	-	-	-	-	-	18
Facebook	66	-	-	-	-	-	8 , 18 , 67
OHC g	5	-	68 , 69	12 , 13	50	-	70 71 72 73 74 75
Weibo	-	32	-	-	-	-	76
Tumblr	-	-	-	-	-	-	18

^aVaccination hesitancy and refusal;

^bCommunicable diseases;

^cSubstance Abuse;

^dPharmacovigilance;

^eSexually transmitted infections;

^fMental health;

^gOnline Health Communities