Why pro-vaccination activists are not good at social media?

Question

It seems that pro-vaccination organizations focus their efforts on organizing meet and greet events. Why are they so weak on social media?

Answer 1

The anti vaxers are the problem. They have single handedly brought back measles, rubella, chicken pox-that were previously wiped out-based on false or debunked information. In my day, I could not go to school w/o those shots-and now I am immune. 

Answer 2

Pro-vaccination is the default position and anti-vaxers are minute minority. So they shouldn't have to organize to defend a position that is basically just common sense.