Tuesday, May 03, 2016

Pediatrics: Maternal Flu Vaccination Extends Protection To Infants

# 11,336

Today we've another, very large, multi-year study that finds substantial immunity to influenza is passed on to the infant - who cannot be immunized until 6 months of age - when the mother gets the flu vaccine during pregnancy.

From the University of Utah Health Sciences press release:

In a study published May 3, 2016, in Pediatrics online, University of Utah School of Medicine researchers reported that infants 6 months and younger whose mothers were vaccinated when pregnant had a 70 percent reduction in laboratory-confirmed flu cases and an 80 percent reduction in flu-related hospitalizations compared with babies whose moms weren't immunized. Health records showed that 97 percent of laboratory-confirmed flu cases occurred in infants whose mom's were not immunized against the disease while pregnant.

You may recall that five years ago, in Pssst! Immunity . . . Pass it On, we saw a study in the American Journal of Obstetrics and Gynecology, that found that maternal receipt of the flu vaccine was linked to more than a 45% reduction in infant hospitalizations with laboratory confirmed flu.

And similarly, in 2010, in Study: Protecting Two With One Shot  we saw a study in the Archives of Pediatric and Adolescent Medicine, that found that that babies born to mothers who received the flu vaccination experienced fewer infections and hospitalizations during their first six months than babies whose mothers did not.

Below you'll find a link and the abstract to today's study.  When you return, I'll have a bit more. 

Julie H. Shakib, Kent Korgenski, Angela P. Presson, Xiaoming Sheng, Michael W. Varner, Andrew T. Pavia, Carrie L. Byington


BACKGROUND: Infants  less than 6 months old with influenza are at risk for adverse outcomes. Our objective was to compare influenza outcomes in infants less than 6 months old born to women who did and did not report influenza vaccine during pregnancy.

METHODS: The study included all women who delivered from 12/2005 to 3/2014 at Intermountain facilities and their infants. Influenza outcomes included infant influenza-like illness (ILI), laboratory-confirmed influenza, and influenza hospitalizations.

RESULTS: The cohort included 245 386 women and 249 387 infants. Overall, 23 383 (10%) pregnant women reported influenza immunization. This number increased from 2.2% before the H1N1 pandemic to 21% postpandemic (P < .001). A total of 866 infants less than 6 months old had ≥1 ILI encounter: 32 (1.34/1000) infants born to women reporting immunization and 834 (3.70/1000) born to women who did not report immunization (relative risk [RR] 0.36; 95% confidence interval [CI], 0.26–0.52; P < .001). A total of 658 infants had laboratory-confirmed influenza: 20 (0.84/1000) born to women reporting immunization and 638 (2.83/1000) born to unimmunized women (RR 0.30; 95% CI, 0.19–0.46; P < .001). A total of 151 infants with laboratory-confirmed influenza were hospitalized: 3 (0.13/1000) born to women reporting immunization and 148 (0.66/1000) born to unimmunized women (RR 0.19; 95% CI, 0.06–0.60; P = .005).

CONCLUSIONS: Self-reported influenza immunization during pregnancy was low but increased after the H1N1 pandemic. Infants born to women reporting influenza immunization during pregnancy had risk reductions of 64% for ILI, 70% for laboratory-confirmed influenza, and 81% for influenza hospitalizations in their first 6 months. Maternal influenza immunization during pregnancy is a public health priority.
  • Accepted March 3, 2016.

The list of maternal vaccination benefits goes on, both in and outside the womb.

Just over a month ago in Clinical Infectious Diseases: Flu Vaccine May Reduce Incidence of Stillbirth we saw a study that found  vaccinated mothers were 51 percent less likely to experience a stillbirth than unvaccinated mothers.

Last year in Pregnancy, Flu and The Next Pandemic we looked at the heightened flu risks for pregnant women, including a 2011 study - BMJ: Perinatal Outcomes After Maternal 2009/H1N1 Infection -  that found that pregnant women admitted to the hospital during the 2009 pandemic with H1N1 saw a 3 to 4 times higher rate of preterm birth, 4 to 5 times greater risk of stillbirth, and a 4 to 6 times higher rate of neonatal death.
Over the past decade we’ve also seen a handful of studies tentatively linking prenatal exposure to influenza (or an influenza-like-illness) with a variety of child and adolescent development disorders (see Of Pregnancy, Flu & Autism).

All of which explains why the CDC, the WHO, and other public health promote the seasonal flu vaccination of pregnant womenMost years, the vaccine provides moderate protection against circulating flu strains, but in the event a pregnant woman becomes infected, studies also show the Benefits Of Early Use of Influenza Antivirals In Pregnancy.