SAN FRANCISCO (FRONTLINE MEDICAL NEWS) – Preterm infants born at 29-35 weeks’ gestation and hospitalized for respiratory syncytial virus (RSV) can experience particularly severe morbidity if they have not received immunoprophylaxis, according to new industry-funded research.

Across two RSV seasons at more than 40 study sites, nearly half of preterm infants admitted for lab-confirmed RSV required ICU admission, and one in five required invasive mechanical ventilation.

“Severity of illness and resource utilization are greatest in infants aged less than 3 months,” said John DeVincenzo, MD, professor in the pediatric infectious diseases division at the University of Tennessee, Memphis. “The results from the two seasons were consistent with one another and with previous and recent studies,” he said at the annual Pediatric Academic Societies meeting.

Previous research has shown that preterm infants born at 35 weeks or less gestation have a higher risk of RSV-related hospitalizations and subsequent morbidity, and that monthly immunoprophylaxis reduced RSV-related hospitalization in high-risk infants, including preterm infants.

Until 2014, the American Academy of Pediatrics recommended respiratory syncytial virus (RSV) immunoprophylaxis for all preterm infants under 32 weeks’ gestation and for infants between 32-35 weeks with additional risk factors, such as chronic lung disease or cyanotic heart disease (Pediatrics. 2003 Dec;112[6]:1442-6).

New recommendations in 2014 restricted immunoprophylaxis to preterm infants younger than 29 weeks’ gestational age unless they had additional risk factors such as chronic lung disease or hemodynamically significant heart disease (Pediatrics. 2014 Aug. doi: 10.1542/peds.2014-1665).

This study compared outcomes among all preterm infants born at 29-35 weeks’ gestation who were hospitalized during RSV season (October-April) for at least 24 hours with laboratory-confirmed RSV and who had not received RSV immunoprophylaxis within the 35 days before symptom onset. The 1,378 infants were younger than age 12 months when they were hospitalized at one of 43 sites during the 2014-2015 RSV season or one of 42 sites in the 2015-2016 season.

Of the 702 preterm infants hospitalized in 2014-2015, 42% were admitted to intensive care, and 20% needed invasive mechanical ventilation. Nearly half (48%) of the 676 infants admitted during the 2015-2016 season went to the ICU, and 19% required mechanical ventilation. One infant died of RSV in each season.

Throughout both seasons, more than three quarters (78%) of all RSV hospitalizations were infants younger than 6 months old. In 2014-2015, infants younger than 6 months accounted for 87% of all RSV admissions to the ICU and 92% of those needing mechanical ventilation. Similarly, young infants accounted for 81% of ICU admissions and 90% of RSV-related mechanical ventilation during the 2015-2016 season. Overall, preterm infants younger than 6 months old without immunoprophylaxis accounted for 84% of RSV-related ICU admissions and 91% of RSV-related mechanical ventilation.

The younger the infants were, the more likely they were to need ICU care and/or mechanical ventilation, the researchers found. Across both seasons, 56% of infants under 3 months old with RSV were admitted to the ICU, compared to 34% of those between 3 and 12 months old. Likewise, 29% of those under 3 months old and 10% of those between 3 and 12 months needed invasive mechanical ventilation.

Nearly half (46%) of all infants hospitalized for RSV had been discharged from their birth hospital within the previous 30 days, and 82% of all hospitalizations occurred within 2 months of birth discharge.

A cost analysis revealed that mean hospital charges for RSV-related hospitalizations of preterm infants ranged from $31,366 for 35-week gestation infants between ages 3-6 months to $122,301 for infants under 3 months old born between 29-32 weeks.

AstraZeneca/MedImmune funded the study. Dr. DeVincenzo and a number of his colleagues have received grants/research support from AstraZeneca/MedImmune, and some of his colleagues are or were AstraZeneca employees.


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