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Do you know that smallpox vaccine is made from inactivated smallpox viruses?. Do you know that polio vaccine is composed of inactive polioviruses?.

Get to know WHY inactive form of microorganisms is used in vaccinating against infections by visiting the link below, You will love it!.

Immunization is the artificial induction of immunity on an individual. This can either be through active or passive means. The last week of April (usually 24-30th of April) is usually dedicated for immunization (often referred to as world immunization week)

Active immunization is the stimulation of the immune system to protect individuals against disease through the use of vaccine.

Passive immunization is the stimulation of immunity on a non-immune individual by administering sensitized lymphoid cells or serum from immune in individuals

Storytime …

History has it that the Chinese and the Turkish were able to reduce the rate of mortality to smallpox among their population through inoculation (whereby scabs from infected individuals were blown through the nostril of healthy individuals to prevent them from getting infected with smallpox). The idea of inoculation of healthy individuals with scabs from infected individuals was introduced to England by Lady Mary Wortley Montagu, the wife of a British ambassador to the Ottoman Empire. Edward Jenner, a British physician observed that people that were previously infected with cowpox were resistant to smallpox infection. In May 14, 1796 he extracted the fluids of pustule from a milkmaid named Serah Nelmes who had been infected with cowpox and injected it into 8-years old James Phipps and observed for symptoms. On the seventh day, he complained of mild cold and a slight headache and recovered completely the following day. Six weeks later, James Phipps was inoculated with extracts from smallpox pustule. The boy showed no symptom of smallpox. He had been completely immune against smallpox. This birthed the beginning of modern-day vaccination. This delightful discovery became a step stool for the discovery of Anthrax, Cholera and Rabies vaccine by Louis Pasteur and many other discoveries by other scientists in the field of medical microbiology.

Types of vaccines

There are two (2) type vaccines:

  1. Inactivated vaccines

This type of vaccine is composed virulent microorganisms made ineffective by either chemicals or irradiation.

  1. Attenuated vaccines

Vaccines are produced from virulent microorganisms grown under adverse conditions are passed through different host until they become avirulent.

Examples of vaccines

The Table Below Shows Bacteria/Viral Agents And Their Vaccines To Prevent Diseases In Humans:

Viral agent Vaccine
varicella zoster virus (Chicken pox virus) Varivax (Attenuated Oka Strain)
Hepatitis A virus Havrix (inactivated virus)
Hepatitis B virus Engerix- B, Recombinant HB (HB viral antigen)
Influenza A virus Inactivated/ live attenuated virus Influenza A virus
Poliovirus Attenuated polio virus
Rabies virus Inactivated rabies virus
Smallpox virus Live attenuated smallpox virus
Yellow fever virus Attenuated Yellow fever virus
Bacterial agent Vaccine
Bacillus anthracis (causal agents of Anthrax) Extracellular components of un-encapsulated B. anthracis
Vibrio cholerae (Cholera) Fraction of Vibrio cholera
Clostridium tetani (causal of Tetanus) Tetanus toxoid
Yersinia pestis (causal of Plague) Fraction of Yersinia pestis
Mycobacterium tuberculosis (Causal of Tuberculosis) Attenuated Mycobacterium bovis (BCG)
Salmonella typhimurium  (Typhoid fever ) Attenuated Salmonella enterica Typh Ty21a
Rickettsia prowazekii (Typhus) Killed Rickettsia prowazekii



Immunity via vaccination is enhanced by B-Cells. When inactivated or attenuated vaccine (composed of weakened infectious agents) is introduced into the body of an unhealthy individual. The humoral immunity mediated by antibodies takes charge. The antibodies which are produced by the B- cells opsonize the target infectious agent (weakened) and present it to T- cells, macrophages that eliminates the bacteria and viruses.

It should, however, be noted that Memory B cells and Memory T-Cells keep long term information pertaining to the vaccine (weakened bacteria/ virus) introduced into the body.

When the body encounter live (active) of such virulent bacteria or virus, the Memory B- cells and T- cells initiates the body to quickly produce antibodies that quickly help to eliminate such infectious agent when the infected person showing symptoms. Thus immunity is conferred vaccinated individuals.


Vaccine: a preparation containing weakened or dead microbes of the kind that cause disease, administered to stimulate the immune system to produce antibodies against that disease

Virulent: pertaining to highly pathogenic or infectious microorganism.

Avirulent: pertains to an un-infectious microorganism

TOXOID: modified toxin from a pathogenic microorganism, which is no longer toxic but is still antigenic and can be used as a vaccine

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