Total Number of Cases that do not Result in Death
We obtained the number of cases per year from the literature on community-acquired pneumonia and publicly available survey data. Using the National Health and Nutrition Examination Survey (NHANES) III, Niederman, et al. (1998) estimate the total number of CAP cases to be 5.6 million per year, or 2.3 percent of the U.S. population. Of these 5.6 million patients, Niederman, et al. (1998) report that 1.135 million are treated as inpatients, and the remaining 4.5 million are treated as outpatients. The National Hospital Discharge Survey (NHDS) (2009), available from the Centers for Disease Control and Prevention (CDC) website, arrives at a similar total of 1.145 million discharges of patients treated for pneumonia, or a rate of 37.4 per 10,000 population. Applied to the U.S. population in 2011, this rate yields an inpatient case count of approximately 1.17 million (National Hospital Discharge Survey, 2009), though these estimates are not limited to pneumonia cases with bacterial causative agents. Subtracting the total number of deaths (51,683) from this estimate (see Section 184.108.40.206), yields a survivor count of approximately 1.12 million per year.
QALYs Lost per Case
We searched the Tufts database for pneumonia and found reasonable QALY weights to be 0.85 for the period of hospitalization and 0.90 for the post-hospitalization period of convalescence (Pepper & Owens, 2002). We then adjusted these weights by period of illness using the following equation:
The average length of stay in the hospital for pneumonia patients is reported in Pepper & Owens (2002) to be 4 days. However, length of hospital stay does not capture additional days spent sick or recovering outside the hospital. Pepper & Owens (2002) also estimate that healthy young adults miss approximately 9 work days due to pneumonia that is treated in the hospital, which includes 4 days in the hospital and 5 days of convalescence. Depending on what day a person gets sick, this may include one or two weekends, so we added 3 days to this convalescence period (1.5 weekends). Thus, the lost QALYs per patient came out to be 0.00384 computed as:
Total QALYs Lost due to Morbidity
Given that lost QALYs per CABP case is 0.00384 and the total number of CABP cases that do not result in death in the US is around 1.12 million, we computed the total annual QALYs lost due to CABP morbidity to be 4,295 in the US.
To calculate VSLY-based illness costs (for patients who do not die), we took the VSLY for the age group containing the average age of a pneumonia inpatient (age 61, VSLY of $290,150), and multiplied it by the average lost QALYs per patient (0.00384) to arrive at a cost of $1,113 per patient. The total morbidity cost due to CABP was then computed at $1.2 billion (= $1,113 × 1,118,000) per annum.