A vaccine is a preparation that provides active acquired immunity to a specific disease. It typically contains a small amount of bacteria, virus or toxin that’s been weakened or killed in the laboratory. Vaccines also contain adjuvants, which help the vaccine reach and activate immune cells. Preservatives and stabilizers, such as sugars or gelatin, keep the active ingredient from degrading during manufacturing and storage.
Vaccines protect you from infectious diseases, which can make you feel miserable and may even kill you. They prevent illness in you, your loved ones and others in your community and around the world. Vaccines can also reduce the strain on healthcare systems by decreasing the number of people who get sick and need to be treated in hospitals.
Some vaccines completely prevent diseases, while others reduce the severity of illness or prevent complications from developing. Research shows that fewer people getting seriously ill from an infectious disease makes it easier for the rest of us to stay healthy and be productive, especially infants and those with weakened immune systems who are most at risk of infection.
Many vaccines require multiple doses, given weeks or months apart, to build up antibodies and memory cells against the pathogen and ensure a strong and long-lasting response to it. Some vaccines cause mild side effects such as a sore arm or fever, but these usually pass quickly and are easy to treat. It’s rare to have a serious allergic reaction to a vaccine, and health workers are trained to spot the signs and treat them immediately.