A disease is an abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not due to any immediate external injury. Diseases are often known to be medical conditions that are associated with specific signs and symptoms.

It is a disorder of structure or function in a human, animal, or plant, especially one that produces specific symptoms or that affects a specific location and is not simply a direct result of physical injury.

A vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins.

The administration of vaccines is called vaccination. Vaccination is the most effective method of preventing infectious diseases; widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the restriction of diseases such as polio, measles, and tetanus from much of the world. The effectiveness of vaccination has been widely studied and verified; for example, vaccines that have proven effective include the influenza vaccine, the HPV vaccine, and the chickenpox vaccine. The World Health Organization (WHO) reports that licensed vaccines are currently available for twenty-five different preventable infections.

Below are the top diseases in the world for which vaccination are currently available as confirmed by WHO;

— Cholera
— COVID-19
— Dengue
— Diphtheria
— Hepatitis
— Haemophilus influenzae type b (Hib)
— Human papillomavirus (HPV)
— Influenza
— Japanese encephalitis
— Malaria
— Measles
— Meningococcal meningitis
— Mumps
— Pertussis
— Pneumococcal disease
— Poliomyelitis
— Rabies
— Rotavirus
— Rubella
— Tetanus
— Tick-borne encephalitis
— Tuberculosis
— Typhoid
— Varicella
— Yellow Fever