What Is Vaccines

Vaccines save millions of lives each year and are among the most cost-effective health interventions ever developed. The immunization vaccines provide has led to many major public health milestones, including the eradication of smallpox, a 74% reduction in worldwide childhood deaths from measles over the past decade, and the near-eradication of polio.

So what is a vaccine? A vaccine is a biological treatment that provides immunity to a particular disease. Vaccines are given when you’re healthy, to keep you from becoming sick. And what’s more—vaccination doesn’t just protect you; it protects everyone who comes into contact with you, including:

  • Old people
  • Children
  • People with weakened immune systems
  • People who can’t be vaccinated for medical or religious reasons

Vaccines work by exposing your immune system to a disease in a controlled way. For instance, a vaccine might contain a dead virus or bacterium, or one that has been weakened so that your immune system can defeat it easily. When you are vaccinated, your immune system encounters the virus or other disease and defends you against it, as if you were sick. Cells in your immune system known as memory cells can “learn” the virus and how to defeat it. Then, if you come into the contact with the disease later, your immune system is prepared.

Some vaccines protect you from common diseases such as chickenpox or influenza (flu). Others protect against very serious diseases such as tetanus (lockjaw) or rabies. Some protect against serious diseases that have almost been eliminated, such as polio. Vaccination against these rare diseases that used to be common can be especially important, because it can prevent a serious outbreak if someone in your community is exposed.

Many vaccinations are given to young children, and some may need to be renewed regularly in adults. You may also need specific vaccines if you’re planning to travel to certain foreign countries, if you’re pregnant, or if you’re planning to get pregnant.

A partial list of diseases that can be prevented by vaccines includes:

  • Anthrax
  • Chickenpox and shingles
  • Hepatitis B
  • HPV (which can cause both genital warts, and lead to cervical cancer)
  • Influenza
  • Lyme disease
  • Measles and German measles (rubella)
  • Mumps
  • Polio
  • Rabies
  • Smallpox
  • Tetanus (lockjaw)
  • Tuberculosis
  • Typhoid fever
  • Whooping cough (pertussis)
  • Yellow fever

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