The nature of vaccines

Dr Maxwell Adeyemi -
Dr Maxwell Adeyemi -


When disease outbreaks occur, researchers work together to investigate and find a cure or vaccine. During their investigation they may extract a specific substance from survivors of the disease which can be used in a healthy person to produce protection or immunity. The substances extracted will not be able to induce a fresh disease in the person.

This substance is called an "antigen" and the protection or immunity is called "antibody”. The compound that affords this antigen and antibody is called a "vaccine" and the administration of it is called “vaccination”.

Antigen, on its own, is any substance that can cause the immune system to produce antibodies against it. By implications, the immune system does not recognise it and tries to fight it. The antigen can be a substance derived from the environment, for example chemicals, viruses, bacteria, pollen or a synthetic product of the original one derived from the causative organism. A vaccine defined as a substance used to stimulate the production of antibodies and provide immunity against one or several diseases, prepared from the causative agent of a disease, its products or a synthetic substitute, treated to act as an antigen without inducing the disease.

Origin of vaccines

In 1796, Dr Edward Jenner, in Berkeley (Gloucestershire), England, took pus from a cowpox lesion on milkmaid’s Sarah Nelmes hand and introduced it into the body of James Phipps – an eight-year-old boy. Six weeks later, he introduced smallpox on two different sites into Phipps' arm with and found that he was not infected. On investigation, it was found that the cowpox earlier introduced into the boy actually made him produce immunity that protected him against a similar infection of smallpox. This was the foundation of modern vaccination or vaccinology.

Vaccines provide the immune system a way to fight an actual diseases in case the body is exposed to it. Immunisation is the process of giving a person a vaccine in order to protect them against disease. The immunity is similar to the one received by getting the disease, except that the person did not wait to get the disease but instead received a vaccine to acquire it.

Many diseases which have affected mankind have been brought under control through administration of drugs including vaccines, among them are cholera, Ebola, lassa fever, meningitis, bubonic plague or black death, smallpox, yellow fever, monkey pox, Sars, influenzas, poliomyelitis (polio).

Covid19 vaccines

Before any drug, including covid19 vaccines, become available on the market, they must pass through many approved standard procedures. This must include the initial laboratory investigation and testing on animals like rats and guinea pigs. This will determine the safety of the drug, the likely effective dose, and the minimal dose that elicit safety risks when administered (toxicity of the drug). Every drug must pass these tests before it is considered for clinical trials on human volunteers. During the clinical trials, the effects of the drug on different parts of human organs are noted and and it can only be released to the public when an acceptable level of tolerance is achieved.

Again, when the drug is released into the market, a post marketing survey will be conducted to observe the effects on a larger population. Once there is any adverse reaction that is considered to be fatal to a reasonable number of the populace, the drug is withdrawn immediately from further circulation.

To get vaccines to control the effects of covid19, up to 200 potential vaccine were tried all over the world. Out of these about 52 went through to human clinical trials, of which the World Health Organization approved the following for immediate use in human:



Johnson & Johnson/Jansen

Astra Zeneca


Doses of covid19 vaccines

The number of doses needed for immunity to protect you against covid19 disease depends on the type of vaccine you take. Each of these companies uses a different technique in their formulation of the vaccines and this controls the provision of the much-needed immunity against the virus.

In the case of Pfizer vaccine, during the clinical trial, the first dose initiates the immune response and the second dose, after one week, enhances the strength of the immunity to 95 per cent. It is therefore recommended that those who took that vaccine should make sure and take the second dose three weeks after the first.

For those who took the Moderna vaccine, based on the clinical trial, it is advisable to take the second dose four weeks after the first dose.

The Astra Zeneca is taken in two doses, at least eight to 12 weeks apart.

The Johnson & Johnson is a one-dose vaccine.

Duration of protection

The exact length of time for protection against covid19 from these vaccines is not yet ascertained because the vaccines are new and studies are ongoing.

Again, due to the existence of variants of the virus which are resistant to the current vaccines, it is advisable to sustain the use of non-pharmaceutical measures such as wearing of mask, social distancing, hand washing, avoiding crowded places, ensuring good ventilation, and maintaining a good level of immunity.

Contact Dr Maxwell on 363-1807


"The nature of vaccines"

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