The Age-Specific Cumulative Incidence of Infection with Pandemic Influenza H1N1 2009 Was Similar in Various Countries Prior to Vaccination

2011

Cumulative Incidence of Pandemic Influenza H1N1 2009 Infection

Sample size: 12 publication 10 minutes Evidence: moderate

Author Information

Author(s): Kelly Heath, Heidi A. Peck, Karen L. Laurie, Peng Wu, Hiroshi Nishiura, Benjamin J. Cowling

Primary Institution: Victorian Infectious Diseases Reference Laboratory (VIDRL), North Melbourne, Victoria, Australia

What is the cumulative incidence of infection with pandemic influenza H1N1 2009 prior to vaccination?

The cumulative incidence of infection with pandemic influenza H1N1 2009 was lower than expected, particularly in older adults.

The cumulative incidence of infection was reported to be 16%-28% in pre-school aged children.
34%-43% of school-aged children were estimated to be infected.
Only 2%-3% of older adults were infected.
The overall population infection rate ranged from 11%-18%.

This study looked at how many people got sick from the H1N1 flu before vaccines were available, and found that fewer people got sick than expected.

The study reviewed 12 serological studies estimating cumulative incidence of H1N1 infection across various countries.

Potential biases due to convenience sampling and the exclusion of certain populations.

The studies included were not all random samples and had varying sampling strategies.

Included various age groups from multiple countries, with a focus on children and adults.

11%-21%

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