Decreased infant influenza disease burden linked to maternal immunization

1. A total of 10% of pregnant mothers received the influenza vaccination during the study period, but this number grew from 2% to 21% after the H1N1 influenza pandemic.

2. Infants born to influenza-immunized mothers had fewer reported influenza-like events, a smaller amount of laboratory-confirmed episodes of influenza, and fewer hospitalizations in the first 6 months than infants born to mothers who were not immunized.

Evidence Rating Level: 2 (Good)

Study Rundown: As infant immunization against the influenza virus does not produce a significant immune response, many organizations have recommended that infants receive passive protection through maternal immunization. Many recent large studies have produced conflicting results as to whether or not this disease burden is reduced in these infants. Authors of the current study sought to examine this relationship and the potential benefits of maternal immunization on influenza outcomes in the first 6 months of infancy. They found that a meager 10% of all mothers received the vaccine during their pregnancy. Furthermore, Infants born to mothers who were vaccinated with the influenza immunization were found to have less influenza-like illnesses, a lower amount of laboratory influenza-confirmed cases, and a decreased number of hospitalizations in the first 6 months of life. This study may be limited by self-report bias for vaccination data, unknown timing of immunizations, unknown strain vaccinations, and the potential of varying immunization effectiveness over the years. However, despite these limitations, the results displayed significant risk reductions in morbidity of this disease and providers should routinely encourage pregnant mothers to receive the influenza vaccination during pregnancy.

Click to read the study, published today in Pediatrics

Relevant Reading: Epidemiology, complications, and cost of hospitalization in children with laboratory-confirmed influenza infection

Study Author, Dr. Julie H. Shakib, DO, MS, MPH, talks to 2 Minute Medicine: University of Utah, Assistant Professor of Pediatrics; Medical Director, Well Baby and Intermediate Nursery; Salt Lake City, Utah.

“Although public health policy and practice have greatly reduced the burden of disease, certain high-risk groups remain susceptible to infectious diseases that can be prevented by vaccines. Infants are at increased risk from vaccine-preventable diseases because they are too young to be adequately immunized. Influenza, a common vaccine-preventable illness, is responsible for substantial morbidity and mortality in infants younger than six months. 

This paper reports influenza-related outcomes in infants born to women who did and did not report influenza immunization during pregnancy. The results indicate that infants born to women who received the vaccine were significantly less likely to be diagnosed with laboratory-confirmed influenza and less likely to be hospitalized for influenza. Current and future physicians should recognize the importance of prioritizing routine preventive care, in this case maternal influenza immunization during pregnancy, to prevent the serious consequences of diseases such as influenza.”

In-Depth [retrospective cohort]: The data from 245,386 mothers and 249,387 infants were included for analysis between 2005 to 2014 from Intermountain Healthcare Facilities in Utah and Idaho. The electronic medical record was surveyed to establish maternal influenza immunization status, laboratory-confirmed infant influenza-like illnesses, as well as infant hospitalizations. A total of 10% of mothers reported receiving the influenza vaccination during their pregnancy. Mothers who had government insurance or no insurance, lived in rural areas, or delivered in the Southwest or Urban South regions were more likely to not have been vaccinated (p < .001). A total of 32 infants of immunized mothers reported influenza-like illnesses versus 834 infants of unvaccinated mothers (RR 0.36; 95% CI, 0.26- 0.52; p < .001). Hospitalizations were seen in 4 maternal-immunized infants compared to 237 non-maternal-immunized infants (RR 0.16; 95% CI, 0.06- 0.43; p < .001). Laboratory-confirmed influenza was reported in 20 maternal-immunized infants and 638 in the opposing group (RR 0.30; 95% CI, 0.19- 0.46; p < .001).

imImage: PD

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