Influenza mortality in the United States, 2009 pandemic: burden, timing and age distribution

In April 2009, the most recent pandemic of influenza A began. We present the first estimates of pandemic mortality based on the newly-released final data on deaths in 2009 and 2010 in the United States. We obtained data on influenza and pneumonia deaths from the National Center for Health Statistics...

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Bibliographic Details
Published in:PloS one 2013-05, Vol.8 (5), p.e64198-e64198
Main Authors: Nguyen, Ann M, Noymer, Andrew
Format: Article
Language:English
Subjects:
Adolescent
Adult
Age
Age composition
Aged
Aged, 80 and over
Antigens
Biology
Child
Child, Preschool
Death
Epidemics
Fatalities
Female
Health aspects
Hostages
Humans
Immunological memory
Infant
Infant, Newborn
Influenza
Influenza A
Influenza, Human - mortality
Male
Mathematical analysis
Medicine
Middle Aged
Mortality
Pandemics
Pneumonia
Pneumonia - mortality
Sex
Social and Behavioral Sciences
Swine flu
United States - epidemiology
Vaccination
Vaccines
Viruses
Young Adult
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Summary:In April 2009, the most recent pandemic of influenza A began. We present the first estimates of pandemic mortality based on the newly-released final data on deaths in 2009 and 2010 in the United States. We obtained data on influenza and pneumonia deaths from the National Center for Health Statistics (NCHS). Age- and sex-specific death rates, and age-standardized death rates, were calculated. Using negative binomial Serfling-type methods, excess mortality was calculated separately by sex and age groups. In many age groups, observed pneumonia and influenza cause-specific mortality rates in October and November 2009 broke month-specific records since 1959 when the current series of detailed US mortality data began. Compared to the typical pattern of seasonal flu deaths, the 2009 pandemic age-specific mortality, as well as influenza-attributable (excess) mortality, skewed much younger. We estimate 2,634 excess pneumonia and influenza deaths in 2009-10; the excess death rate in 2009 was 0.79 per 100,000. Pandemic influenza mortality skews younger than seasonal influenza. This can be explained by a protective effect due to antigenic cycling. When older cohorts have been previously exposed to a similar antigen, immune memory results in lower death rates at older ages. Age-targeted vaccination of younger people should be considered in future pandemics.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0064198