Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.

Of the estimated 2 million heroin users in the United States, 600,000–800,000 are considered hardcore addicts. Heroin addiction is considered to be one of the hardest addictions to recover from.

The immune system needs 9.5 hours of sleep in total darkness to recharge completely.

Asthma attacks and symptoms usually get started by specific triggers (such as viruses, allergies, gases, and air particles). You should talk to your doctor about these triggers and find ways to avoid or get rid of them.