What is Passive Immunity?

Mary McMahon
Mary McMahon

Passive immunity is a form of immunity which occurs when antibodies are transferred from one person to another individual, or when antibodies of animal origin are introduced to a human. This type of immunity is short acting, and is typically seen in cases where a patient needs immediate protection from something and he or she cannot form antibodies quickly enough independently.

The presence of microbes and antigens inside of the body usually triggers the body's immune response.
The presence of microbes and antigens inside of the body usually triggers the body's immune response.

In natural passive immunity, antibodies are passed from a mother to a child. Antibodies can be transferred through the placenta, or transmitted through the colostrum, a liquid which is produced in the breasts for a baby's first meal. The antibodies transmitted through the colostrum and placenta generally only last for several weeks, which is long enough to allow the baby to start to build up its own immune system and to make its own antibodies.

Antibodies can be transferred from mother to child through the placenta.
Antibodies can be transferred from mother to child through the placenta.

Artificial passive immunity involves the introduction of antibodies through means such as injection. For example, in the treatment of some diseases, patients may be given a serum derived from patients who have recovered to help them fight the disease. This practice is sometimes seen when people are dealing with an outbreak of a new or extremely virulent disease for which no known treatment is available.

Prophylactic treatments of antibodies are sometimes given when people are exposed to diseases like rabies, botulism, tetanus, and diphtheria. By giving a patient passive immunity, a doctor can help the patient recover from a disease which the patient's body is unable to fight. This type of immunity is not the same thing as vaccination, a process in which small amounts of antigens are introduced to the body to encourage it to form its own antibodies so that it can fight those antigens in the future.

When the body makes its own antigens, as seen when someone is vaccinated, this is known as active immunity. Active immunity lasts much longer than passive immunity, sometimes persisting over a lifetime to keep someone from getting sick, in marked contrast with the temporary state of passive immunity. Inducing active immunity is often preferred, when possible, because it will support the patient's health in the long term. However, artificially creating active immunity is very complicated, as it involved the controlled introduction of antigens in the body, and this can be dangerous for some patients, as seen when so-called "live" vaccines cause outbreaks.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Very interesting that the antibodies trasfered through mother only last for weeks. I'm a nurse and prior to entering nursing school, I was immunized Hep B, varicella, rubella, you name it. I got it as a requirement for school entrance. Almost a year later I got pregnant. My question is: how much of that immunity actually was passed down to my child? I am very skeptical about having him immunized now. What would be the wise choice?

I feel I want him to have a blood test done that will show what he is immunized too, and if so will that type of test be performed?


This is a really good article for giving an overview of the difference between active and passive immunity. I'd just like to add that the whole active vs passive immunity is basically made possible by T cells.

In active immunity, the body responds to a threat, and then keeps some of the T cells essentially as memory cells, to trigger the same immune response when the next attack comes.

This is why people who have immuno-compromised systems are at such a risk. Though it sounds a little ridiculous, if your immune system isn't working, then you can actually die of cold, or be made severely ill by the bacteria that exist naturally in your own body.

So that's why its so important to have both your active and passive immunity standards high -- without a proper immune system, your body is essentially a fish in a barrel for disease and infection.


Thanks for this article -- there was a botulism scare at my work last year, and I kept hearing the terms passive and active immunity bandied around, but I really couldn't ever figure out the difference between passive and active immunity -- as long as I'm immune somehow, I don't really care if it's active or passive!

But it is interesting to know what those terms actually mean, and to see how doctors would apply different vaccines or prophylactics in certain situations. I had no idea that the human body could have so many different versions of immunity, and this really opened my eyes.

Thanks, wisegeek.


How interesting. I had heard about all the good nutrition that a baby can get from it's mother's milk, but I had no idea that it could actually experience a passive immunity while breastfeeding.

Very, very interesting.

I also had no idea that the whole rabies/botulism injections thing wasn't an active immunity. For some reason, I had thought that after you got the shots, you had an acquired immunity to such conditions, since you had had such a high dosage of antibodies put into your body to fight them.

Again, very interesting and informative article -- keep it up!

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