Prevention of viral diseases began many years ago without knowledge of an agent. Smallpox, caused by the variola virus, haunted humanity for millennia. In 30% of cases, smallpox was lethal, while the survivors were protected from re-infection. Inoculation with smallpox pustules named variolation was practiced as a prevention measure despite carrying risk of severe infection. An observation was made that milkmaids seemed protected from smallpox and the hypothesis was postulated that an exposure to a similar virus, in this case cowpox, grants protection against smallpox. In a brave experiment, Edward Jenner, an 18th century British physician, inoculated an 8-year old with a cowpox, a closely related cow virus the milkmaids were exposed to. The boy was challenged 2 months later with a matter from a smallpox lesion and the boy did not develop any disease. The practice of cowpox inoculation led to a protection from smallpox in a safe manner. This was the first immunization conducted and because it involved a cow virus, a process was named vaccination, derived from Lattin word vacca, meaning cow [1, 2]. 

Fast forward to 2023, currently we have vaccines for 25 diseases, these are called vaccine preventable diseases:  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 [3]. 


2.  WHO. A brief history of vaccination.  09-Dec-2023]; Available from: brief-history-of-vaccination.

3.WHO. Vaccine-Preventable Diseases. [cited 2023; Available from: