Immunization

Immunization is the process by which individuals are made immune to diseases, typically through vaccination. It aims to stimulate protective immune responses without causing the disease. Immunization programs use vaccines to reduce the burden of infectious diseases and are a core component of public health.

How vaccines work: vaccines present antigens or genetic material that triggers an immune response. The body produces antibodies and memory B and T cells, enabling rapid response upon future exposure. Some vaccines provide passive immunity by transferring antibodies; most vaccines confer active, long-lasting protection.

Types of vaccines: inactivated, live-attenuated, subunit, toxoid, conjugate, mRNA, viral vector. Vaccines may require one or more doses and boosters to maintain protection.

Administration and safety: Delivered through injections or oral/nasal routes. Schedules are age-based and risk-based. Adverse events are monitored; most are minor, serious events are rare. Contraindications include severe allergy to vaccine components; pregnant status varies by vaccine; immunocompromised.

Impact and access: Programs aim for high coverage to achieve herd immunity and reduce outbreaks. Global initiatives address access disparities, routine childhood immunization, and vaccine-preventable disease elimination or eradication (e.g., polio). Surveillance and vaccination data guide policy.

Controversy and ethics: Vaccine hesitancy, misinformation, mandates, and exemptions raise ethical and public health considerations. Safety communication emphasizes transparency and evidence.