A vaccine is a preparation of weakened or killed microorganisms, such as bacteria or viruses, or parts of them that are administered to a person or animal in order to stimulate immune response and provide immunity against a specific disease. Vaccines are typically administered through injection, inhalation, or orally.
Vaccines have been used since the late 1700s to protect against infectious diseases such as smallpox, polio, measles, and rubella. Today, vaccines are widely used to prevent a variety of illnesses, including mumps, diphtheria, whooping cough, and tetanus. Vaccines can also be used to protect against certain types of cancer, such as cervical cancer and liver cancer.
Vaccines work by stimulating the immune system to produce antibodies that recognize and destroy the disease-causing microorganism. This response helps the body recognize and fight off similar microorganisms in the future.
In addition to preventing disease, vaccines can reduce the severity of some illnesses by providing partial or complete immunity. This can reduce the spread of disease from person to person, and reduce the risk of complications from diseases.
Vaccines are considered one of the most successful public health interventions in history. Vaccination programs have saved millions of lives, and continue to reduce the incidence and severity of many infectious diseases.