Pediatricians can protect your child by administering not only active immunizations, but sometimes they can use what physicians call passive immunizations. If you hear your pediatrician use these terms, this is what they mean.
When your child receives an active immunization, the vaccine prevents an infectious disease by activating the body’s production of antibodies that can fight off invading bacteria or viruses. Passive immunization, in which antibodies against a particular infectious agent are given directly to the child or adult, is sometimes appropriate. These antibodies are taken from a donor and then processed so the final preparation contains high antibody concentrations. At that point, they are given in the vein or by shot to the patient.
Passive immunization is often used in children and adults who have weakened immune systems or may not be good candidates for routine vaccinations for other reasons. It can be used with people who haven’t been vaccinated against a disease to which they’ve been exposed. For example, the passive rabies immunization (rabies immune globulin) is commonly used after a certain type of wild animal bites a child. Passive immunizations for hepatitis A (gamma globulin) may be helpful for people traveling to a part of the world where hepatitis A is common. They are typically given before children or adults leave on their trip. These are used less now that there is a vaccine for hepatitis A.
If there is enough time, the active vaccination is preferable. Keep in mind that passive immunizations provide only short-term protection that often lasts just a few weeks before the antibodies are worn down and removed from the bloodstream. By contrast, active immunizations can produce antibodies that last a lifetime.