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Previous flu exposure increases risk in later pandemics
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Patients who were born during the 1957 influenza pandemic appeared to face an increased risk of death in later pandemics, according to researchers in Canada.
They wrote that this surge in mortality had historical precedents in other pandemics.
“Reported situations in which previous influenza virus exposures have enhanced susceptibility are rare and poorly understood, Matthew S. Miller, PhD, assistant professor of biochemistry at McMaster University, said in a press release. “This study’s results have important implications for pandemic risk assessment and should inform laboratory studies aimed at uncovering what’s responsible for this effect.”
The researchers analyzed data on monthly mortality and influenza circulation in the United States and Mexico from October 1997 to July 2014, evaluating levels of excess mortality across age groups in various influenza pandemics.
During the 2009 H1N1 pandemic, the researchers found “a surprising increase” in mortality among patients born from 1949 to 1964, particularly among those born in 1957 — the year of an H2N2 pandemic. A spike mortality also occurred in this age cohort during the resurgent 2013-2014 H1N1 outbreak.
This phenomenon also occurred during the 1918 influenza pandemic, when patients who were born during an 1890 pandemic of heterosubtypic H3Nx influenza demonstrated the greatest excess mortality, and again in 1968, when patients born during the 1918 pandemic faced higher mortality, the researchers reported.
“We suggest the phenomenon of 1918 is not unique,” Miller said. “We believe that exposure to pandemic influenza early in life is a risk factor for mortality during subsequent cross-strain pandemics.”
Miller added that additional research of improved influenza vaccines is warranted.
“We believe there is an important piece missing in this puzzle that has been overlooked in most investigations on pandemic influenza,” he said. “Our research highlights the urgent need to develop more broadly protective ‘universal’ influenza virus vaccines — capable of providing protection against both seasonal and pandemic influenza strains.” – by Andy Polhamus
Disclosures: The authors report no relevant financial disclosures.
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