How Do Vaccines Work?

Vaccines are usually given to children by shots, although some may be taken by mouth, such as the polio vaccine. Adults can also receive immunizations in the form of vaccines to boost their immune system and fight disease. How do vaccines work to boost our immunity and to fight potential diseases? Why are childhood vaccines necessary? Which diseases can be prevented by vaccines?

How do Vaccines Work?

Immunization or vaccines work by tricking your body to believe that it is being invaded by an infectious microorganism, triggering the immune system to strengthen its defenses. Vaccination involves injecting a harmless form of a germ to the body, to which your immune system responds, producing antibodies to counter-attack the intruders. A memory of the “invasion” is created so the immune system can easily recognize, attack, and neutralize the real disease-causing agents when they invade.

Immunity from Extra Doses

Complete immunity is often built up after one is given several doses of a particular vaccine. For example, according to WHO (World Health Organization), polio vaccine should be given at birth. Other vaccines given at birth are BCG for childhood tuberculosis and hepatitis B vaccine in countries where these diseases are common.

Extra doses of Polio vaccine are usually given on the 6th, 10th and 14th weeks after birth together with a combination of other vaccines like diphtheria, pertussis, and tetanus (DPT). Measles vaccines are usually given at the age of nine months because of inherited immunity. Children from high-risk places are also given yellow fever vaccine at this time.

Eliminating Disease

Vaccinations can help eliminate disease as more people are immunized. An example is smallpox, which has disappeared, after which the vaccination program has been stopped.

A greater number of people have to be immunized to beat highly infectious diseases such as measles. This disease starts to spread rapidly when vaccination rates decrease. To stop disease from spreading, at least 90% of the children have to be immunized. Furthermore, if 95% of kids are protected by the measles, mumps and rubella (MMR) vaccine, these three diseases may be eliminated.

Watch the following video for how vaccines work:

Types of Vaccines

There are many types of vaccine:

  • The OPV or oral polio vaccine contains live, but weakened viruses that stimulate the body to produce antibodies, without causing disease.
  • The pertussis vaccine contains killed or inactivated viruses that also trigger an immune response from the body.
  • Mothers and newborn babies are given tetanus toxoid vaccine (TT), which consists of a modified version of the toxin produced by the virus.
  • Hib or Haemophilus influenzae type b (Hib) vaccine consists only of the cell components of the bacteria, which trigger an immune response.

Why Are Childhood Vaccines Necessary?

  • Maternal immunity may be passed to newborn babies but this immunity soon goes away during their first year of life. Natural immunity against other diseases is not available, including whooping cough.
  • When a child is not vaccinated and exposed to an infectious germ, his body may not be able to fight against the disease. Many children used to die from diseases such as measles, whooping cough, and polio.
  • Immunizing children also helps protect community as a whole including very young babies who cannot be vaccinated (like children with leukemia or children under one year old), and those who cannot respond to vaccination.

Which Diseases Can Be Prevented by Vaccines?

Vaccine comes from the Latin word “vacca”, which means cow. The first vaccine was discovered by Dr Edward Jenner, who used cowpox viruses to stimulate people’s immune systems against a more harmful virus called smallpox. The wide use of smallpox vaccine helped eliminate the disease. At present, there are many diseases that can be effectively prevented by immunization and these include the following:

Vaccine-Preventable Diseases (source: CDC)



Cervical Cancer

Hepatitis B

Hepatitis A

Human Papillomavirus (HPV)

H. influenza type b

Japanese encephalitis



Lyme disease

Monkey pox














Yellow Fever


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