Some vaccines, such as MMR, are not given at 2, 4, and 6 months. What explains this scheduling?

Some vaccines, such as MMR, are not given at 2, 4, and 6 months. What explains this scheduling?

• A. Febrile seizures are more likely in younger infants with some vaccines.
• B. Maternal antibodies neutralize some vaccines and are delayed until 12 months.
• C. The risk of adverse effects is lower for some vaccines after the first year.
• D. Too many vaccines at once can overwhelm the infant's immune system.

Answer: (B)

Maternal antibodies present in infancy can neutralize certain vaccines, especially live attenuated ones, before the baby’s own immune system can respond. These maternal IgG antibodies wane over the first year of life, so giving a live vaccine too early may lead to a poor or absent immune response. Measles, mumps, and rubella vaccines are live vaccines, so they’re scheduled for later—around 12 months—when maternal antibody levels have declined enough for the vaccine to provoke a robust immune response. Other vaccines given in the first months are chosen for early protection and are less affected by maternal antibodies, which is why they can be administered at 2, 4, and 6 months.

Maternal antibodies present in infancy can neutralize certain vaccines, especially live attenuated ones, before the baby’s own immune system can respond. These maternal IgG antibodies wane over the first year of life, so giving a live vaccine too early may lead to a poor or absent immune response. Measles, mumps, and rubella vaccines are live vaccines, so they’re scheduled for later—around 12 months—when maternal antibody levels have declined enough for the vaccine to provoke a robust immune response. Other vaccines given in the first months are chosen for early protection and are less affected by maternal antibodies, which is why they can be administered at 2, 4, and 6 months.