Probabilities of H1N1 influenza illnesses, hospitalizations, and deaths by age and risk status.

LR = lower-risk; HR = higher-risk.1Data from seasonal influenza illness was used to estimate the ratio of high risk to low risk based on expert opinion that although the incidence for pH1N1 and seasonal influenza varied substantially by age, the conditional probability of influenza-related complications for high risk and low risk patients would likely be similar for pH1N1 and seasonal (i.e., within an age group, high risk patients would be more likely to experience influenza-related complications than low-risk patients for both pH1N1 and seasonal influenza).