How Does Active and Passive Immunity Work?

How Does Active and Passive Immunity Work?

Active immunity is a natural process that protects you from certain infections. It works by building antibodies for specific diseases. For example, if you've ever been infected with normal influenza, you won't develop an antibody against other types of fever, and vice versa. The buildup of antibodies does not occur immediately after infection; it can take days or weeks to develop and last for a lifetime.


Natural immunity is the body's natural ability to protect itself against germs and viruses. This protection varies according to the germ and individual. For example, a person with measles has a stronger natural immunity than someone who has never had it. Natural immunity can weaken after a mild illness, though. Moreover, it will not last as long as the protective immunity provided by the COVID-19 vaccine.

Herd immunity

The percentage of the population that is immune to disease is called the herd immunity threshold. Once this threshold is reached, the number of infected individuals is so small that the population no longer participates in the chain of transmission. This prevents an endemic disease from spreading and is also called community immunity. Herd immunity is vital protection against disease, but it is not an absolute requirement for effective protection.

Passive immunity

Innate immunity is the first line of defence against germs and is present from birth. It is composed of special cells and proteins that recognize and kill germs. However, this system doesn't communicate this information to the rest of the body, which is why it is ineffective against reinfection.

Innate immunity

Innate immunity is the first line of defence when exposed to infectious agents. It is initiated within hours and provides a rapid array of defences. Adaptive immune responses are then induced in the first weeks of infection. The induction of acquired immunity requires selected innate responses, including activation of DCs, initiation of antigen processing, migration to draining lymph nodes, and upregulation of co-stimulatory molecules.

Artificial passive immunity

Passive immunity is acquired by vaccination with antibodies that can be naturally produced in the body or artificially manufactured in a laboratory. These antibodies can be used for therapeutic purposes or as an emergency treatment if the body has become infected with a disease. These antibodies can be administered after rabies or Hepatitis B infection or can be produced in humans.

Induced passive immunity

Passive immunity refers to the body's ability to protect itself from infection by attacking foreign microorganisms. It is the opposite of active immunity, which occurs when an individual or organism experiences something new and creates antibodies to destroy the invaders. Passive immunity lasts only a few weeks or months, while active immunity lasts long.