Vaccines that successfully prevent severe infant respiratory virus diseases should induce protection at a very young age because of the low age of patients who are hospitalized owing to these viruses. Candidate respiratory virus vaccines are being tested in infants who are naïve to infection but seropositive to the viral agents because they possess maternal IgG antibodies (Abs). Transplacental maternal Abs may be partially protective against disease caused by respiratory virus infections. Carefully conducted studies have shown that these Abs can also profoundly suppress or enhance infant immune responses to immunization. The mechanisms underlying regulation of immune responses to viruses by maternal Abs are under investigation. This article explores the current knowledge regarding the effect of maternal Abs on respiratory virus and measles virus immunization, and it reviews the current approaches to overcoming Ab-mediated immunosuppression.