Setting

A live bat was discovered in the sink in an open design, level 4 NICU located on the top floor of an 8-story hospital in Central Texas. Austin is home to millions of bats, including the reputed largest urban bat colony in the world. ¹ The 2 surrounding counties have the highest confirmed rabies case numbers in bats in Texas, far exceeding the other 252 counties. This bat and a second bat found flying in the nonpatient hallway were captured and released outdoors by plant operations staff before rabies testing could be performed.

The infection prevention and pediatric infectious diseases teams were contacted to advise on the incident.

Patients

The NICU where the exposure occurred has 44 beds; 28 of which were occupied at the time of the exposure. No direct contact with the bat was noted by any staff member and there were no visible bites on any of these infants. Cases of rabies transmitted by bats have occurred even in the absence of a documented bite, which may go unnoticed.Reference Monroe, Yager and Blanton ³ Rabies PEP is recommended in cases of exposure to bats in infants and young children even in the absence of an obvious bite. ⁴

In an attempt to quantify risk, each patient in the NICU at the time of the exposure was given a risk score. Neonates who were unclothed in open warmers were described as “high risk”; neonates in open warmers who were swaddled with only the face and head exposed were described as “low risk”; and neonates in incubators were considered to be at “no risk.” Of the 28 infants, 6 were categorized as high risk, 13 as low risk, and the remaining 9 as no risk of exposure. Patient characteristics are summarized in Table 1.

TABLE 1

Patient Characteristics and Outcomes

NOTE. PEP, post-exposure prophylaxis.

^a Full course defined as HRIG+vaccine at 0, 3, 7, 14, and 28 d.

^b Adequate response defined as≥0.5 IU/mL.

Intervention

A thorough review of the literature and government recommendations on rabies did not reveal any evidence for safety and efficacy of rabies PEP in premature infants whose immune systems may be quite immature. Conflicting results were found regarding a newborn or premature infant’s ability to respond to vaccines.Reference Demirjian and Levy ^{5 ,} Reference Tavares, Ribeiro and Oliveira ⁶ Furthermore, inadequate response to rabies PEP has been documented in immunocompromised patients.Reference Kopel, Oren, Sidi and David ⁷ Rabies infection is essentially 100% fatal in the absence of immunoprophylaxis; therefore, there are no expressed contraindications to the rabies PEP.Reference Fayaz, Simani and Fallahian ^{8 , 9} The Texas Department of State Health Services as well as the Centers for Disease Control and Prevention (CDC) rabies experts were contacted for additional guidance. Given the fatal consequences of a rabies exposure and the fact that the bats were not available for rabies testing, the team concluded that rabies PEP was warranted for at least some of the infants.

The decision was made to recommend rabies PEP to all 6 of the high-risk infants and to offer rabies PEP to the 13 infants at low risk. Patient families were informed in writing of the known risks of possible exposure to rabies and that the risks and efficacy regarding administration of rabies PEP to preterm infants were unknown. The final decision to undergo prophylaxis was left to the parents. The families of 5 of the 6 infants at high risk and 2 infants at low risk consented to the administration of rabies PEP.

The standard recommendations for rabies PEP administration in adults and children at risk of exposure (including suspected contact with bats) were applied: human rabies immune globulin (HRIG) 20 IU/kg given intramuscularly (IM), and a 4-dose rabies vaccine series: 1 mL IM dose on days 0, 3, 7, and 14 in the anterolateral thigh. A fifth dose given at 28 days was included based on the assumption of decreased immunocompetence due to prematurity. ^{9 , 10}

All 5 of the high-risk infants who participated completed the entire series, including the HRIG and 5 doses of the vaccine. In addition, 1 of the low-risk infants completed the HRIG and 3 doses of the vaccine and the second participating low-risk infant received the HRIG and 1 dose of the vaccine prior to discharge. Despite scheduled follow-up, these 2 infants did not return to complete the series at this facility.

Families were instructed to follow-up 6 months after completing the series with the pediatric infectious diseases clinic to assess the response to the rabies PEP via serum rabies vaccine titers. Of the 5 patients who completed rabies PEP, 3 returned for the recommended 6-month follow-up.