Vaccination (VACC) is the administration of antigenic material, known as a vaccine, to stimulate the immune system and protect against infectious diseases. The aim is to provide active immunity by inducing specific antibodies and memory cells that recognize and neutralize pathogens upon future exposure.
How vaccination works and types of vaccines
When a vaccine is injected or taken orally or nasally, dendritic cells take up the antigen and present it to T cells, leading to the activation of B cells that produce neutralizing antibodies. Vaccines also stimulate cytotoxic T lymphocytes that kill infected cells. The immune system then forms memory B and T cells that respond rapidly upon later exposure to the same pathogen. Vaccines can be live attenuated, which contain weakened forms of the pathogen; inactivated, containing killed organisms; subunit or recombinant, comprising purified proteins; toxoid, made from inactivated toxins; conjugate vaccines, where polysaccharides are linked to proteins; and newer platforms such as mRNA and viral vector vaccines that deliver genetic instructions for producing antigenic proteins. Adjuvants are often added to enhance the immune response. Immunization schedules often require booster doses to maintain immunity, and herd immunity can be achieved when a large portion of a population is vaccinated, reducing pathogen circulation.
Notable vaccination examples and public health impact
Smallpox vaccination using vaccinia virus led to the global eradication of smallpox by 1980. Oral polio vaccines have nearly eliminated poliomyelitis worldwide, with only a few endemic countries remaining. Measles, mumps and rubella vaccines given in combination prevent these highly contagious childhood infections. Human papillomavirus vaccines protect against strains of HPV associated with cervical cancer. Seasonal influenza vaccines are updated each year to match circulating strains, reducing morbidity and mortality. During the COVID-19 pandemic, mRNA and viral vector vaccines targeting SARS-CoV-2 were developed and deployed in record time, dramatically reducing severe disease and deaths when widely administered. A robust immunization program protects individuals and communities by preventing the spread of infectious diseases. Vaccination remains one of the most effective public health interventions, saving millions of lives and reducing healthcare costs worldwide. Related Terms: Vaccine, Immunization, Antigen, Immune response, Herd immunity