What Are Vaccines, And Why Are They Not Given Intravenously?

coronavirus vaccine


Antibodies are proteins capable of killing any bacteria or virus that enters the human body. Production of a specific type of antibody against a particular disease takes place when a person is vaccinated.

An antigen is a substance that causes your body to produce antibodies. An antigenic element induces your body to produce antibodies.

Vaccines are biological substances that contain antigenic components. The human body produces antibodies against the antigenic component with every injection of a vaccine. The person who received the vaccine will not get sick because the antigen is a killed or weakened bacteria, virus, or microorganism. After vaccination, your body has developed antibodies against a particular disease-causing microorganism. Exposed to the active disease, you will not get sick because your body is prepared and has antibodies against it. Said antibodies keep circulating in your body, protecting you from future exposure to the same disease.

Types of vaccines

Live attenuated vaccin
  • Inactivated vaccines. These vaccines also fight viruses and bacteria. Inactivated or killed viruses or bacteria serve as the antigens in these vaccines. Polio and the Sinovac Covid-19 vaccines are examples of this type.
Inactivatd vaccines
Inactivated vaccines
  • Toxoid vaccines. The antigen placed in the vaccine is a toxoid (weakened toxin). Hence, this type of vaccine neutralizes toxin-producing bacteria. When the immune system meets a toxoid, it learns how to fight the natural poison. These are the vaccines used for diphtheria and tetanus toxins.
  • Subunit vaccines. The antigen placed in the vaccine is a part of the virus or bacteria instead of the whole germ. For this reason, side effects are minimal. It prevents pertussis or whooping cough.
  • Conjugate vaccines. They fight a particular group of bacteria with antigens covered by sugar-like substances known as polysaccharides. The coating prevents the immature immune system of children from recognizing an antigen. Hence, the conjugate vaccine connects to the polysaccharide, an antigen that the immunity system can recognize and respond to accordingly. This vaccine prevents Haemophilus influenza.
  • mRNA vaccines. These vaccines contain mRNAs that teach your cells to produce spike proteins. When your immune system recognizes the spike proteins, your body produces antibodies against them. When the active COVID-19 disease enters your body, the antibodies formed before your infection will fight them off. Hence, you will not show the clinical manifestations of COVID-19 infection. Examples of mRNA vaccines are the Pfizer-BioNTech and Moderna Covid-19 vaccines.
mRNA covid-19 vaccines
mRNA covid-19 vaccines
  • Viral vector vaccines. These vaccines contain adenoviruses, each one carrying DNA. When this adenovirus enters the host’s cell, it goes near its nucleus and injects the DNA inside. This DNA then produces the mRNA affecting the multiplication of T cells and inducing the B cells to generate the necessary antibodies. Examples of this are the Oxford-AstraZeneca, Sputnik V, and the Johnson and Johnson Covid-19 vaccines.

Routes of administration

  • Intramuscular. One of the muscles receives the vaccine injection.
  • Intradermal. A part of the skin takes in the vaccine injection.
  • Subcutaneous. An area under the skin serves as a reception for the vaccine. 
Intramuscular, subcutaneons, intravenous, intradermis

Reasons for not administering vaccine via the intravenous route


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