Passive immunization, or passive immunotherapy, is a process in which individuals receive antibodies from another source rather than producing those antibodies on their own. Passive immunity provides short-term protection against infection.
Antibodies are proteins that bind to and help attack pathogens, such as bacteria and viruses. They are a key component of the human immune system.
Typically, antibodies are produced by white blood cells in response to infection. But scientists have also developed ways to use antibodies to prevent disease. Vaccines, for example, trigger the production of antibodies in order to "teach" the immune system to fight future illness. Passive immunization provides similar, although usually temporary, protection by "donating" antibodies, derived from humans or animals, to a vulnerable individual.
Passive immunity can develop naturally, such as when a mother's antibodies are transferred to a growing fetus or nursing infant. It also can occur artificially when antibodies that protect against specific pathogens are transferred, often via blood or plasma transfusion.
Several products have been approved by the U.S. Food and Drug Administration (FDA) for passive immunization and immunotherapy, including antibodies against botulism, diphtheria, hepatitis A, hepatitis B, measles, rabies, Kawasaki disease, and tetanus.
What are the advantages and disadvantages of passive immunization and immunotherapy?
Passive immunization and immunotherapy are particularly helpful for individuals who are immunocompromised and therefore cannot mount their own immune response. Passive immunization also works quickly, providing protection within hours or days, whereas vaccines can take weeks or months if boosting (more than one injection) is required. Unlike vaccination, however, passive immunization and immunotherapy do not result in immunological memory; the protection they provide lasts for a comparatively short amount of time. Also, the transfer of antibodies from animals or other people can cause side effects including severe allergic reactions.
Can passive immunization and immunotherapy be used to treat or prevent COVID-19?
Investigators at Caltech and at other research institutions are currently analyzing samples from people who have recovered from infections by SARS-CoV-2 or similar viruses to determine if their antibodies could serve as therapeutic tools.