Table 3.

Analysis of blog posts by date of publication.

	Total	2006–2009	2010–2012	2013–2015
	N (%)	N (%)	N (%)	N (%)	p
Total comments	698	360	174	150
Uses evidence	50 (7.2)	25 (6.9)	16 (9.2)	9 (6.0)	0.506
Strongly encourages vaccination	49 (7.0)	16 (4.4)	11 (6.3)	19 (12.7)	0.003
Strongly discourages vaccination	132 (18.9)	83 (23.1)	28 (16.1)	18 (12.0)	0.008
Mentions…
Natural remedies to boost immunity	45 (6.4)	19 (5.3)	18 (10.3)	8 (5.3)	0.068
Signs and symptoms of adverse reaction	74 (10.6)	5 (1.4)	0 (0.0)	0 (0.0)	0.278*
Autism	38 (5.4)	24 (6.7)	8 (4.6)	5 (3.3)	0.273
Thimerosal or mercury in vaccines	10 (1.4)	10 (2.8)	0 (0.0)	0 (0.0)	0.010*
Sudden Infant Death Syndrome, Guillain-Barre Syndrome, or other medical condition	46 (6.6)	24 (6.7)	11 (6.3)	10 (6.7)	0.988
Overloading immune system with too many vaccines at once	12 (1.7)	3 (0.8)	4 (2.3)	5 (3.3)	0.105*
Herd immunity	4 (0.6)	0 (0.0)	0 (0.0)	2 (1.3)	0.048*
Risk of illness being less than risk of adverse reaction	10 (1.4)	7 (1.9)	1 (0.6)	2 (1.3)	0.585*
Risks not being fully disclosed or understood	7 (1.0)	7 (1.9)	0 (0.0)	0 (0.0)	0.042*
Delaying vaccination from recommended scheduling	33 (4.7)	14 (3.9)	7 (4.0)	12 (8.0)	0.121
Political immunization mandates for school entry	22 (3.2)	8 (2.2)	8 (4.6)	5 (3.3)	0.293*
Condescending attitudes of doctors when refusing vaccines	26 (3.7)	20 (5.6)	4 (2.3)	2 (1.3)	0.037
Trusting doctors' opinions and recommendations toward vaccines	18 (2.6)	10 (2.8)	4 (2.3)	3 (2.0)	0.948*
Profit motivations of pharmaceutical industry	22 (3.2)	13 (3.6)	3 (1.7)	5 (3.3)	0.532*
Distrust of government	23 (3.3)	15 (4.2)	2 (1.1)	6 (4.0)	0.171
Entanglement of government and pharmaceutical industry	29 (4.2)	15 (4.2)	8 (4.6)	6 (4.0)	0.968

N = 16 blog posts in 2006–2009; N = 16 posts in 2010–2012; N = 12 posts in 2013–2015

^*Fisher-exact test used instead of chi-square test.