Which finding contraindicates administering the first MMR immunization to a 15-month-old child?

The administration of the MMR (measles, mumps, and rubella) vaccine can be contraindicated in certain situations, particularly related to the child’s immune status. In the case of a child with congenital immunodeficiency, the immune system may not function properly, making the child unable to adequately respond to the vaccine. Live vaccines like MMR are designed to stimulate an immune response; however, in individuals with compromised immune systems, there is a risk of vaccine-related complications and insufficient immunogenicity.

In comparison, a fever may indicate an underlying illness but does not typically contraindicate vaccination as it can still be safe to vaccinate. A recent cold usually does not affect the safety or efficacy of the vaccine, and being on antibiotics is not a contraindication since antibiotics do not interfere with the body’s immune response to vaccines. Therefore, the only strong contraindication in this scenario is the presence of a congenital immunodeficiency, which requires careful consideration and alternative immunization strategies.