Any baby born before the 37th week of pregnancy is considered to be preterm. About 12 percent of births in the U.S. are preterm.
Preterm babies acquire lesser quantities of antibodies through the placenta than full-term babies. Since these antibodies are present at lower levels, they do not last as long as those of full-term babies. Because preterm infants rely on their own immune systems for protection sooner than full-term babies, it is important that they receive needed vaccinations so they can protect themselves against disease.
Vaccines should be given according to a baby's chronologic age — the time since delivery.
Preterm infants of mothers infected with hepatitis B should receive the hepatitis B vaccine at or shortly after birth. If the baby weighs less than 2,000 grams, the dose should not be counted as part of the hepatitis B series, and the baby should start the three-dose series one month after birth.
Preterm infants of mothers who are not infected with hepatitis B should get the vaccine one month after birth.
Preterm babies discharged before 1 month of age may get the vaccine at discharge as long as they are considered medically stable and have been consistently gaining weight.
In both cases, later doses should be given at least 4 weeks after the dose at 1 month. The third dose should be given at least 16 weeks after the first dose and at least 8 weeks after the last dose, but not before 6 months of age.
In addition to hepatitis B, 2-month-old babies require vaccination against diphtheria, tetanus, pertussis, polio, Haemophilus influenzae type b, pneumococcus, and rotavirus. Preterm infants should receive these vaccines at the chronologic age of 2 months, even if they are still hospitalized.
These vaccines should continue to be given at the appropriate chronologic ages according to the Centers for Disease Control and Prevention's vaccine schedule, until each series is completed.
Other vaccines should also be given according to the recommended schedule; these include vaccines for measles, mumps, rubella, varicella, and hepatitis A.
Influenza vaccine is not recommended until 6 months of age. At 6 months of age, the baby may get the inactivated version of the vaccine. Healthcare workers and family members in contact with a baby less than 6 months old should be immunized to lessen the baby's chance of being infected with influenza.
Updated: January 2013
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