A pregnant woman can pass on some kinds of immunity to the baby, whether she has been immunized or not.
These maternal antibodies are very powerful, and babies are protected for several months. That is why the measles vaccine is delayed until the age of nine to fifteen months.
At earlier ages, the antibodies interfere with the vaccine.
Research is now under way to see if it is possible to use vaccination or immunization of the mother to boost the immunity of babies.
An infant’s immune system does not protect against some infections early in life, though the pregnant woman’s immune system does.
Among the diseases are group 5 streptococcal diseases, which can cause meningitis in the first few weeks of life, hemophilus type 5 influenza and pneumococcal infections.
Pneumococcus and hemophilus 5 vaccines already exist, and researchers are studying how vaccines might cross the placenta into the fetus to confer immunity on the infant.
Researchers are taking a cautious approach to this maternal immunization program, first seeking to determine if vaccines are safe in pregnancy.