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Introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) a decade ago in France was associated with a significant reduction in acute chest syndrome (ACS) for children with sickle cell disease, a cohort study showed.

From 2010 to 2019, incidence of ACS dropped from an estimated 7.3 to 4.5 cases per 1,000 children with sickle cell disease, reported Naïm Ouldali, MD, PhD, of Robert Debré University Hospital in Paris, and colleagues.

This difference represented a 0.9% monthly decrease (P<0.001 for slope), and an estimated cumulative reduction of 41.8% over the full study period, according to the findings in .

"These results provide new evidence of the key role of Streptococcus pneumoniae in ACS and should be considered when estimating the public health benefit of current and next-generation pneumococcal conjugate vaccines in children," the group wrote.

Children with sickle cell disease are 100 times more likely to be infected by S. pneumoniae compared to children without the disease. And while the precise role of S. pneumoniae in ACS remains unclear, the reduction in incidence observed in the study following PCV13 implementation suggests "an important pneumococcal involvement," the group wrote.

ACS is a life-threatening complication for patients with sickle cell disease that can result in lung injury, breathing difficulty, and low oxygen to the rest of the body. It occurs when sickled cells block blood and oxygen from reaching the lungs and can be triggered by a viral or bacterial infection.

In June 2010, the French immunization program recommended a shift from the 7-valent pneumococcal conjugate vaccine (PCV7) to PCV13 for all children younger than 2 years of age. The authors noted that since 2011, PCV13 coverage by age 2 has been greater than 90% in the general population.

The cohort study used patient records from a national hospital-based French surveillance system. All 107,694 children with sickle cell disease hospitalized in France from January 2007 to December 2019 were included. Patients had a median age of 9 years and 52% were boys.

Overall, ACS occurred in 3.7% of the children (n=4,007), pneumonia in 1.7%, other lower respiratory tract infections (LRTIs) in 1.1%, asthma crises in 0.8%, acute pyelonephritis in 0.8%, and vaso-occlusive crises in about two-thirds.

Median age of patients with ACS tended to be older (8 years) than those with pneumonia (4 years), asthma crises (5 years), or other LRTIs (1 year). And the seasonal pattern was different, with ACS incidence decreasing by 21.2% in summer compared with winter, versus a 41.9% decrease for pneumonia, an 80% decrease for other LRTIs, and a 13.8% decrease for asthma crises.

Monthly incidence of ACS following PCV13 implementation was similar across age groups; no changes in the incidence of vaso-occlusive crises, asthma crises, or acute pyelonephritis were observed over the study period.

Intensive care unit (ICU) admission and ventilation rates were highest with ACS (21.7% and 23.6%, respectively), followed by pneumonia (5.1% and 6.4%), asthma crises (2.4% and 2.4%), and other LRTIs (1.5% and 1.7%).

"The proportion of ventilatory support and ICU transfer among patients with ACS did not significantly change following PCV13 implementation, suggesting that the severity of the disease remained unchanged," noted Ouldali and colleagues.

In total, 117 hospital deaths occurred, including 18 from ACS, with the vast majority caused by vaso-occlusive crises or other diagnoses.

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