Immunization safety in preterm infants

Findings of a new study should alleviate concern that immunization puts preterm infants at risk for clinical deterioration.

The retrospective investigation analyzed the occurrence of respiratory decompensation within 72 hours after immunization in a cohort of 240 premature infants (<32 weeks’ gestational age) admitted to the neonatal intensive care unit (NICU) at Children’s Healthcare of Atlanta at Egleston, Atlanta, Georgia.

Because infants with bronchopulmonary dysplasia (BPD) are at highest risk for severe complications related to vaccine-preventable diseases and also are often thought to be particularly at risk for adverse events after immunization, the difference in the rate of respiratory decompensation after immunization in subgroups of 170 babies with BPD and 70 babies without BPD was compared as the primary outcome measure. Respiratory decompensation was defined as a composite of increased fraction of inspired oxygen (FiO2) greater than or equal to 10% above the previous 24-hour mean or increased respiratory support within 72 hours of administration.

The results showed that the vast majority of the infants with and without BPD tolerated immunization well and did not require respiratory support. The primary outcome analysis found the rate of respiratory decompensation was not significantly different comparing the infants with and without BPD (8% vs 5%, respectively; P=.65).

In addition, secondary outcome analyses showed no statistically significant differences between the BPD and no-BPD subgroups in the rates of increased FiO2 greater than or equal to 10% above the previous 24-hour mean (1% vs 0%, respectively; P=.58); increased respiratory support within 72 hours of immunization (7% vs 5%, respectively; P=.65); or apnea, bradycardia, and desaturation events (29% vs 25%, respectively; P=.51).

E Clark Montague, DO, is lead author of the paper and Neonatal-Perinatal Medicine Fellow at Emory University, Atlanta, Georgia. He tells Contemporary Pediatrics, “Neonatologists expect parents and pediatricians to immunize our patients in the outpatient setting according to the recommended schedule. While these infants are in the hospital, we have the ability to continuously monitor them and quickly intervene if something adverse were to happen, but that occurs only rarely based on our study. We, therefore, believe neonatologists should feel confident in immunizing these patients in a timely manner and according to the recommended schedule.”

Motivation for the research stemmed from findings of a number of studies showing that a significant proportion of premature infants are discharged from NICUs either underimmunized or on a delayed immunization schedule. Review of the timing of immunization within the current study’s patient population is consistent with those reports, Montague says.

“In our population, the average age at immunization was approximately 2 weeks later than that recommended by the Advisory Committee on Immunization Practices and the American Academy of Pediatrics. By not immunizing infants in a timely manner while they are under our care, we may be placing them at risk for unnecessary exposure to preventable infections and relying on the pediatrician to get them caught up,” he notes. 

In designing the study, the investigators hoped they might be able to identify specific risk factors for decompensation following immunization with the idea that clinicians could use the information to recognize infants at low risk who could be immunized without hesitation. However, the study lacked sufficient power to identify whether any of the variables analyzed independently increased risk.

“We did find that infants who had a history of apnea, bradycardia, or desaturation episodes prior to immunization were more likely to have an increased number of episodes following immunization. This increase in frequency of episodes, however, did not equate to infants requiring increased respiratory support following immunization, and therefore it was not of clinical significance,” Montague says.

The investigators believe that certain features of their study design reinforce the safety of immunizing preterm infants. First, their study population of infants referred to a tertiary NICU for subspecialty evaluation likely represents a group of the most ill premature babies who also are probably at highest risk of respiratory decompensation. In addition, a very strict definition of respiratory decompensation was used in order to capture all infants experiencing clinically relevant decompensation.

The investigators acknowledge that reliance on data abstraction from healthcare providers’ documentation is one of the limitations of their study. Furthermore, there is a potential for selection bias as it is possible physicians chose to immunize babies based on their assessment of the infant’s health and ability to tolerate an adverse event. “Therefore, our study may not reflect the true number of infants who experience respiratory decompensation following immunization if all infants were immunized according to the recommended schedule,” Montague explains. 

REFERENCE

Montague EC, Hilinski JA, Williams HO, McCracken CE, Giannopoulos HT, Piazza AJ. Respiratory decompensation and immunization of preterm infants. Pediatrics. 2016;137(5). pii: e20154225. Epub ahead of print.

Ms Krader has 30 years’ experience as a medical writer. She has worked as both a hospital pharmacist and a clinical researcher/writer for the pharmaceutical industry and is presently a freelance writer in Deerfield, Illinois. She has nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article.