Screening, Baseline Characteristics, Pre-Vaccine Characteristics and Supportive Care
A total of 146 infants admitted to the NICU eligible for their 2-month vaccine series were screened. After excluding 19 infants who were >37 weeks gestational age or received vaccinations over 2 days, 127 infants were included (pre-practice change n=52, 40.9%; post-practice change n=75, 59.1%)[Figure 1].The population was 48.8% male, with an average gestational age of 28.6 weeks (28 weeks vs. 29.3 weeks, p=0.06). On average, infants in the pre-practice change group were smaller at birth, both by weight in kilograms (kg; 0.94 kg vs. 1.2 kg, p=0.047) and length in centimeters (cm; 35 cm vs. 37 cm, p=0.039). Other baseline characteristics were similar between groups, except that more infants in the pre-practice change group had a history of a positive culture (29, 55.8% vs. 24, 32%; p=0.008) [Table 1].
The median weight at time of vaccination was 2.59 kilograms, and not significantly different between groups (2.49 kg vs. 2.6 kg, p=0.719). At baseline (48 hours prior to vaccination), 26 infants had ≥1 episode of apnea or bradycardia prior to vaccination, 9 in the pre-practice change group and 17 in the post-practice change group (17.3% vs. 22.7%, p=0.462) [Table 2].
APAP was commonly used as supportive care among the whole cohort; 29.9% of the cohort received a one-time dose of APAP and 27.6% received scheduled doses of APAP. There was significantly greater use of single-dose APAP in the post-practice change group (9, 17.3% vs. 29. 38.7%; p=0.01), but no difference in the use of scheduled APAP (11, 21.2% vs. 24, 32%; p=0.179). Only one patient in the total cohort received LMX [Table 2].
Primary and Secondary Outcomes
37% of the total cohort had ≥1 episode of apnea or bradycardia (19, 36.5% vs. 28, 37.3%; p=0.927). There were a total of 8 episodes of prolonged apnea, 4 in the pre-practice change cohort and 4 in the post-practice change cohort (7.7% vs. 5.3%, p=0.715); 40 episodes of prolonged bradycardia, 15 in the pre-practice change cohort and 25 in the post-practice change cohort (28.8% vs. 33.3%, p=0.592), and 18 episodes of severe events, 9 in the pre-practice change cohort and 9 in the post-practice change cohort (17.3% vs. 12%, p=0.399). The overall patient cohort had median NPASS scores of 0, with no significant differences between groups. The incidence of fever, number of patients on respiratory support, escalation of respiratory support, and median FiO2 was not different between groups. Infants in the pre-practice change cohort were more likely to have a sepsis workup done with 48 hours of immunization (5, 9.6% vs. 1, 1.3%; p=0.042). Enteral feeds were not held in any infants. The median time to vaccine series completion was 5 days in infants prior to the practice change, associated with a significant reduction in vaccine schedule interruptions (13, 25% vs. 0; p<0.001) [Table 3].
Univariate Analysis
We performed a univariate analysis to identify predictors for severe events in infants within 48 hours of vaccination [Table 4]. Predictors of severe events included younger gestational age, smaller birth weight, smaller birth length, and higher baseline apnea or bradycardia events at baseline.