Under Vaccination of Premature Infants
Giving birth to a child before their due date can be stressful, especially if your infant requires a stay in the neonatal intensive care unit. Amidst all the excitement at the birth of your newborn, you will be faced with many decisions regarding their healthcare. One of these vitally important decisions is when to vaccinate your child. For the majority of preterm infants who do not have any other conditions that might contraindicate the use of vaccines, the Centers for Disease Control recommends following the regular childhood immunization schedule based on your child’s chronological age (1). This means that regardless of how many weeks early your child was born, you can safely take them to the doctor to get their vaccines on time. This can be confusing for a number of reasons, so let’s delve into this more carefully.
Chronological age versus corrected for gestational age
Chronological age is your child’s age starting at birth. This is completely separate from the gestational age, which is either the number of days from the first day of your last menstrual cycle until your child was born or it is estimated based on your first trimester ultrasound. Premature infants are those who were born at less than 37 weeks gestation. Pediatricians will use your child’s chronological age for some metrics, and age corrected for gestational age for others. For example, if your child was born eight weeks early, when they turn 6-months-old, they will only be expected to meet the milestones of a 4-month-old to be considered developmentally normal. On the other hand, the immunization schedule for preterm infants is identical to the standard schedule for full-term infants, regardless of their gestational age at birth. This recommendation is made based on a longstanding and growing body of literature showing that clinically-well, preterm infants can have similar protective immune responses to childhood vaccines compared to full-term infants (1). The one exception is that low birth weight preterm infants do not have as robust a response to the hepatitis B vaccine at birth; however, by one month of age, these infants are able to develop an appropriate immune response to the vaccine (2).
Preterm infants are more likely to be undervaccinated
A recent study by Hofstetter, et al. found that a greater proportion of preterm infants are undervaccinated compared to their full term peers at the same chronological age (3). This study was a retrospective study that gathered information from the Washington State Immunization Information System and the electronic medical record for infants born between 2008-2013. The study found that fewer preterm infants (47.5%) were up to date on their vaccines by 19-months-old compared to their full-term infant peers (54.0%) (3). Similarly, at 36-months-old, only 63.6% of preterm infants were fully vaccinated compared to 71.3% of full-term infants (3). The authors of this study did not conclude any specific reasons for these findings; however, they referenced several other studies that have delved into potential contributing factors. These factors include parent and healthcare provider knowledge of CDC guidelines for vaccination schedule, parents’ perception in regard to their preterm infant’s development and readiness for vaccination, and greater frequency and complexity of health care issues associated with prematurity (3). This study demonstrated the need for increased awareness of the recommended vaccination schedule as well as the necessity for developing strategies to improve timely vaccination of preterm infants.
What this means for you and your premature child
It is safe for your healthy preterm infant to receive their vaccines on a chronological age schedule with their peers born at full-term. If they are preterm, low birth weight and requiring a hospital admission, they may not receive their first birth dose of the hepatitis B vaccine until they are being discharged from the hospital, and they will need three additional doses starting after one month of age to ensure that they are fully vaccinated. Otherwise, the data supports that preterm infants have adequate protective responses to childhood immunizations. This is great news for your preterm child, who will be at risk for the same infectious diseases as their similarly aged friends. Your child will have the best chance of being immunologically protected before they are exposed to these pathogens, if they receive their vaccinations on time.
1. General Best Practice Guidelines for Immunization: Best Practices Guidance of the Advisory Committee on Immunization Practices (ACIP). <https://www.cdc.gov/vaccines/hcp/acip-recs/general-recs/special-situations.html>.
2. Mast EE, Margolis HS, Fiore AE, et al. A comprehensive immunization strategy to eliminate transmission of hepatitis B virus infection in the United States: recommendations of the Advisory Committee on Immunization Practices (ACIP) part 1: immunization of infants, children, and adolescents. MMWR Recomm Rep. 2005;54(RR-16):1-31. <https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5416a1.htm>.
3. Hofstetter, et al. “Early Childhood Vaccination Status of Preterm Infants.” Pediatrics. 09 Sep 2019;144:3. <https://pediatrics.aappublications.org/content/144/3/e20183520>.