Estimated impact of maternal vaccination on global paediatric influenza-related in-hospital mortality: A retrospective case series

BACKGROUND: Influenza virus infection is an important cause of under-five mortality.

Maternal vaccination protects children younger than 3 months of age from influenza infection.

However, it is unknown to what extent paediatric influenza-related mortality may be prevented by a maternal vaccine since global age-stratified mortality data are lacking.

METHODS: We invited clinicians and researchers to share clinical and demographic characteristics from children younger than 5 years who died with laboratory-confirmed influenza infection between January 1, 1995 and March 31, 2020.

We evaluated the potential impact of maternal vaccination by estimating the number of children younger than 3 months with in-hospital influenza-related death using published global mortality estimates.

FINDINGS: We included 314 children from 31 countries.

Comorbidities were present in 166 (53%) children and 41 (13%) children were born prematurely.

Median age at death was 8·6 (IQR 4·5–16·6), 11·5 (IQR 4·3–24·0), and 15·5 (IQR 7·4–27·0) months for children from low- and lower-middle-income countries (LMICs), upper-middle-income countries (UMICs), and high-income countries (HICs), respectively.

The proportion of children younger than 3 months at time of death was 17% in LMICs, 12% in UMICs, and 7% in HICs.

We estimated that 3339 annual influenza-related in-hospital deaths occur in the first 3 months of life globally.

INTERPRETATION: In our study, less than 20% of children is younger than 3 months at time of influenza-related death.

Although maternal influenza vaccination may impact maternal and infant influenza disease burden, additional immunisation strategies are needed to prevent global influenza-related childhood mortality.

The missing data, global coverage, and data quality in this study should be taken into consideration for further interpretation of the results.

FUNDING: Bill & Melinda Gates Foundation.