Photo Credit – CDC
#19,050
During the 1918 pandemic an abnormally high number of pregnant women died from the influenza, and those that survived endured a very high miscarriage rate. Again, during the much milder 1957 Asian Flu, pregnant women reportedly suffered disproportionately higher mortality rates than non-pregnant women of the same age.Historical reviews of both events are available in a Perspective, written by 3 CDC physicians (Sonja A. Rasmussen, Denise J. Jamieson, Joseph S. Bresee) and published in the CDC Journal of EID article, Pandemic Influenza and Pregnant Women in February of 2008.
A year after its publication, the arrival of the 2009 H1N1 pandemic saw similarly high rates of influenza complications among pregnant women, often with tragic results.
- During the 2009 H1N1 pandemic, pregnant women were six times more likely to be hospitalized than non-pregnant women (see Pregnancy & Flu: A Bad Combination).
- And in 2011, in BMJ: Perinatal Outcomes After Maternal 2009/H1N1 Infection we saw a study where pregnant women who were admitted to the hospital with an H1N1 infection experienced 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.
Admittedly, this data is biased towards hospitalized cases with severe disease, and many other pregnant women with milder infections likely saw less dire outcomes.
Despite these dangers, pregnant women and young children are often the last cohort to be approved to receive a novel flu (or CoV) vaccine, since most early clinical trials exclude them over safety concerns.
All of which brings us to a narrative review article published in Viruses that looks at the limited data we have on novel flu and pregnancy, and argues that H5N1 could be particularly dangerous to pregnant women and their offsprings if it should begin to spread in humans.
The authors propose a basic algorithm for initial clinical management of suspected H5N1 in pregnancy and lobby for prioritizing both antivirals and vaccines (when available) for high-risk patients, including those who may be pregnant.
I've only posted the abstract and a few excerpts, so follow the link to read it in its entirety. I'll have a bit more after the break.
Avian Influenza H5N1 Infection During Pregnancy: Preparing for the Next Flu Pandemic and Improving Perinatal Outcomes
Matthew J. Zuber1,2,*, Callie L. Brown2,3 and Cara B. Janusz2,4
Viruses2026, 18(2), 212; https://doi.org/10.3390/v18020212
AbstractInfluenza (flu) is a common respiratory virus with seasonal global spread. Zoonotic viruses can occasionally cross species, leading to pandemic-level spread, and for flu viruses, this is considered an “antigenic shift”. The flu can be particularly severe during pregnancy due to immune system adaptations that occur during pregnancy, with prior global pandemics causing excess hospitalizations, deaths, and other complications in the mothers and the neonates.
We aim to review the current literature with respect to novel avian H5N1 and the potential impact of infection with flu during pregnancy. A systematic literature search was conducted.
Here we provide a rapid summary of epidemiology and understanding of viral spread, published risks of H5N1 in pregnancy, the unique physiologic, cellular, and molecular adaptations making H5N1 infection unique in pregnancy, implementation of an effective vaccine program in event of a pandemic specific to pregnant individuals, optimizing peripartum care for infected individuals, and direction for future research to direct vaccine strategy and mitigate risks in a future flu pandemic.
(SNIP)
Pregnancy has long been recognized as a risk factor for severe disease. Historically, pregnant persons have suffered increased rates of morbidity and mortality compared to their non-pregnant peers during the last several flu A pandemics of the past century, most recently during the 2009 H1N1 pandemic [2]. Similarly, pregnant persons had elevated morbidity and mortality during the recent COVID-19 pandemic [3]. Vaccine clinical trials continue to routinely exclude pregnant persons, creating substantial limitations in closing equitable care gaps for pregnancy and generating robust and early data during a pandemic to help support vaccine programs for pregnant persons at heightened risk for severe disease.
(SNIP)
(SNIP)
7. Conclusions
While there is limited data on H5N1 or novel avian influenza viruses’ effects during pregnancy, the available data suggest we should prepare for and anticipate cases of severe disease in the perinatal setting in the event of a future global pandemic. We outlined here the current epidemiology, unique pathophysiology of the disease in the setting of pregnancy, suggested clinical approach during pregnancy and birth, and suggested future directions regarding vaccine research and policy approaches to vaccination strategy. As new viral strains evolve, so should the approach in pregnancy management and close surveillance that will help mitigate risk and improve perinatal outcomes.
While COVID hit the elderly the hardest (see CIDRAP Older adults made up 90% of US COVID deaths in 2023), there are reasons to believe that an H5Nx pandemic might severely impact a much younger cohort (see Preprint: Immune History Shapes Human Antibody Responses to H5N1 Influenza viruses).
As far back as 2007 - in A Predilection For The Young - we looked at the disturbing skewing of H5N1 cases (and deaths) among younger individuals (see WHO Chart below).
We've seen similar patterns in past pandemics, including in 1918 and again in 2009. Here is what the CDC had to say about the impact of the 2009 pandemic virus in 2012's First Global Estimates of 2009 H1N1 Pandemic Mortality Released by CDC-Led Collaboration.
2009 H1N1 Pandemic Hits the Young Especially Hard
This study estimated that 80% of 2009 H1N1 deaths were in people younger than 65 years of age which differs from typical seasonal influenza epidemics during which 80-90% of deaths are estimated to occur in people 65 years of age and older.
Complicating matters, vaccine hesitancy continues to grow, with nearly a 33% drop in uptake of influenza vaccine by pregnant women since 2019.
While an H5 pandemic is by no means assured, these are two (of many) reasons why HPAI H5 might have an even greater impact on society than COVID.
