medwireNews: Infants born early preterm – before 32 weeks’ gestation – have a higher rate of acute lower respiratory infections (ALRIs) caused by respiratory syncytial virus (RSV) than the general infant population, show the results of a systematic review and meta-analysis of global data.
The findings also show that babies born early preterm have a significantly increased risk for hospitalization as a result of RSV-associated ALRIs, compared with the general population, and that this increased risk lasts into their second year of life.
“Overall, preterm infants accounted for 25% [...] of hospitalisations due to RSV-associated ALRI in all infants of any gestational age,” write Harish Nair, from the University of Edinburgh in the UK, and colleagues in The Lancet.
They used data from 47 published studies reporting global or regional estimates of RSV-associated morbidity and mortality in preterm infants and young children, and 17 providing individual participant data. From this, they estimated worldwide RSV-associated ALRI incidence in the community, resulting hospitalizations, in-hospital mortality, and overall mortality among children younger than 2 years old born prematurely between 1995 and 2021.
Nair and colleagues found that incidence rates of RSV-associated ALRI declined overall between 2000 and 2019, but in 2019 there were 1,646,000 episodes of RSV-associated ALRIs in the community among early preterm infants up to 12 months of age.
There were also 533,000 RSV-associated hospital admissions in these infants and 26,760 RSV-attributable deaths, of which 3050 (11%) occurred in hospital.
David Torres-Fernandez and Quique Bassat, both from the University of Barcelona in Spain, stress in a related comment that this is “an unacceptably high global burden,” and highlight the fact that 93% of these episodes were in developing countries, “underscoring the tremendous burden of disease gap existing between socioeconomic strata.”
They add: “Preterm infants are particularly at risk and encounter additional hindrances in [low-income and middle-income countries] due to reduced access to quality prenatal, maternal, and neonatal care, nutritional deficiencies, higher risk of concomitant infections, or a generalised difficulty to handle chronic conditions.”
The researchers found that preterm infants overall had similar rates of RSV-associated ALRIs to the general infant population. However, when they assessed early preterm infants and late preterm (32 to 37 weeks’ gestation) infants separately, there was a significantly higher incidence of RSV-associated ALRIs only among early preterm infants relative to all infants within the first 6 months (167.0 vs 96.3 per 1000 person–years) and from 6 months up to 12 months (138.9 vs 82.6 per 1000 person–years), with incidence rate ratios of 1.74 and 1.69, respectively.
Early preterm infants had similar rates of RSV-associated ALRIs as all infants in the second year of life (66.6 vs 59.4 per 1000 person–years), and the rates in late preterm infants were similar to all infants in the first 6 months, from 6 months up to 12 months of age, and in the second year of life.
The risk for hospital admission for RSV-associated ALRIs was a significant 3.87-fold higher for early preterm infants versus all infants in the first 6 months of life (78.1 vs 20.2 per 1000 person–years). This trend persisted into the second year of life, when the risk increased 2.26 times in children aged between 1 and up to 2 years relative to all infants, at rates of 10.7 versus 4.7 per 1000 person–years.
In late preterm infants, the risk for hospitalization for RSV-associated ALRIs was only significantly increased relative to all infants in the first 6 months of life, when the admission rate was 38.9 per 1000 person–years, equating to a 1.93-fold increased risk.
Nair and co-workers analyzed common RSV-specific risk factors and found that maternal smoking during pregnancy (odds ratio [OR]=1.68), having two or more children in the household under 5 years old (OR=1.80), and multiple births (OR=1.71) all conferred significant independent risk for developing RSV-associated ALRI in the community in all infants.
By comparison, the risk for hospitalization for RSV-associated ALRIs was increased in infants with underlying medical conditions, including congenital heart disease, tracheostomy, bronchopulmonary dysplasia, chronic lung disease, and Down syndrome, with ORs ranging from 1.40 to 4.23.
“As governments begin to consider including RSV vaccines in national immunisation programmes, understanding the global disease burden of (and the risk factors for) RSV-associated ALRI in preterm infants and young children is essential for the design of an optimal RSV prophylaxis strategy,” conclude Nair et al.
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Lancet 2024; doi:10.1016/S0140-6736(24)00138-7
Lancet 2024; doi:10.1016/ S0140-6736(24)00254-X