The Centers for Disease Control and Prevention pulled back a public health campaign promoting the flu vaccine as cases of the flu have surged in recent weeks. The now-defunct “Wild to Mild ...

Flu vaccine effectiveness in South America was 35% against hospitalization. ... A CDC spokesperson said that the effectiveness of the vaccine for H1N1 was "within the range" of previous seasons.

Two types of influenza viruses are responsible for seasonal flu outbreaks: Influenza A and B. Influenza A accounts for around 75 percent of all cases and tends to cause more severe illness in adults.