Immunizations

Immunizations are medical interventions that prevent infectious diseases by training the immune system to recognize and combat specific pathogens. They are typically delivered as vaccines, which present harmless components or instructions that resemble a pathogen, prompting protective immune responses without causing disease.

Most vaccines activate active immunity, teaching the body to respond to future infections. In some cases, passive immunization provides immediate, temporary protection by giving antibodies directly. Vaccines vary in platform, including live attenuated, inactivated, subunit, toxoid, conjugate, and newer approaches such as mRNA and viral vectors.

Common vaccines protect against diseases such as measles, mumps, rubella, polio, tetanus, diphtheria, pertussis, hepatitis B, human papillomavirus, and influenza. Immunization programs establish routine schedules for children, with boosters for some vaccines and additional recommendations for adults, pregnant people, and high-risk groups.

Safety and effectiveness are established through preclinical studies, phased clinical trials, and post-licensure surveillance. Most adverse effects are mild and transient; serious events are rare. Routine contraindications exist for certain conditions or severe allergic reactions, and healthcare providers distinguish when vaccines should be postponed.

Vaccination has substantially reduced the burden of many diseases and, in some cases, eradicated them. High coverage supports herd immunity, protecting those who cannot be vaccinated and reducing outbreaks. Public health efforts address access, equity, and misinformation to maintain confidence in immunization.