Which of the following is an example of passive immunity?

Passive immunity refers to the temporary immunity that is acquired when antibodies are transferred from another individual. The most common example of this type of immunity is maternal antibodies, which are passed from a mother to her child, either in utero through the placenta or via breastfeeding. These antibodies provide immediate but short-term protection against infections during the early months of life, helping to safeguard the newborn who has not yet developed its own immune responses.

In contrast, contracting measles would provide active immunity, as the person’s immune system responds to the infection by producing its own antibodies. Vaccination, such as with the hepatitis B vaccine, also induces active immunity; the vaccine stimulates the immune system to produce a protective response against the virus. The skin barrier, while critical for defense against pathogens, does not constitute an antibody-mediated immune response and is therefore not an example of passive immunity.

Understanding passive immunity is crucial in the context of vaccination and immune system development, particularly in newborns and infants who rely on maternal antibodies until they can effectively respond to vaccinations and develop their own immune functions.