 When an infant is born, it is too young to be immunized from diseases such as measles, mumps, rubella, or whooping cough. If those who come into close contact with the infant such as family, doctors, and friends are all vaccinated, the infant will be safe from dangerous diseases. There is very little chance of an outbreak when a large portion of the community is immunized. This is known as herd immunity. This herd immunity protects those with weaker immunity, even if a close family member was never vaccinated. But notice what happens when a few more people choose not to immunize their children. Perhaps they heard that vaccines cause autism, an idea that was popularized by an influential 1996 paper that has since been disproven. When less people are immunized, widespread outbreaks can occur. Because of this, people with weakened immunity, such as the elderly or infants, can be infected. Even if an infant's mother ensures that she herself is immunized, the infant, who is still too young to be vaccinated, is susceptible to dangerous diseases when others in the community choose not to vaccinate. When people stop immunizing, fatal diseases that were once eradicated make a comeback. In order for herd immunity to be effective, approximately 95% of the population must be vaccinated. Choosing not to immunize is a decision that affects those around you. That is why it is important to ensure that you and your family members are immunized.