Mike, 22, a heroin addict who began using opiates when he was 13, pauses to shoot-up by a railway underpass in the Kensington section of Philadelphia, which has become a hub for heroin use. | Spencer Platt/Getty Images

Opioid Vaccines Could Make the Brain Immune to Heroin

Heroin and fentanyl vaccines aim to use the body’s own immune system to block addictive chemicals from entering the brain.