• There are two types of immunity; active immunity and passive immunity. 
• Immunization is the process of receiving immunity artificially that can protect the individual from certain diseases.
• Immunization can be done through serum, antiserum, and vaccines.

Active immunity

• This immunity stays for a long period.
• There are two types; natural active immunity and artificial active immunity.

Natural active immunity

• This immunity is obtained when the individual recovers from the disease after the first exposure to the pathogen.
• Memory cells are able to remember the infection from the first exposure.
• If the same pathogen infects the body for the second time, the immune system will respond rapidly.
• The number of antibodies will increase and be produced rapidly to stop the infection.

Artificial active immunity

• Immunity is acquired by injecting antigens into the body to stimulate lymphocytes to produce antibodies against the antigen.
• This type of immunity is known as vaccination.

Passive immunity

• Provide protection on certain diseases for a short period.
• Antibodies are obtained from the external source and these antibodies will be excreted after a period of time.
• There are two types of passive immunity; natural passive immunity and artificial passive immunity. 

Natural passive immunity

• Obtained by the baby that receives the antibodies through placenta and breastmilk. 
• Provide full protection to the baby until the immune system of the baby can take over the task.

Artificial passive immunity

• Obtained through serum injection that contains certain antibodies to destroy the antigens. 
• This type of immunity provides immediate protection for short period.