Table 1.
Epidemiological and healthcare resource use model inputs
| Category/input | Base-case value | Range | Source | |
|---|---|---|---|---|
| Lower bound | Upper bound | |||
| Population size (N), overall and by age | 2023 US population projections from US Census Bureau [21] | |||
| ≥ 60 years | 82,862,258 | – | – | |
| 60–64 years | 21,307,839 | – | – | |
| 65–69 years | 19,378,641 | – | – | |
| 70–74 years | 15,796,904 | – | – | |
| 75–79 years | 11,805,733 | – | – | |
| 80–84 years | 7,489,487 | – | – | |
| 85–89 years | 4,213,769 | – | – | |
| ≥ 90 years | 2,869,885 | – | – | |
| Annual probability of all-cause mortalitya | Probability of dying by single year of age | Arias et al. [22] | ||
| Annual incidence of symptomatic RSV-ARI per person year at riskb | 0.0465 | 0.0272 | 0.0627 | Calculated from Falsey et al. [2] and DiazGranados et al. [23] |
| Seasonality adjustment factor for symptomatic RSV-ARI infectionc | 3.0–286.7% | NREVSS (2018–2019) [25] | ||
| Percentage of symptomatic RSV-ARI cases that are RSV-LRTDd | 47.6% | 41.9% | 53.3% | AReSVi-006 phase 3 clinical study [20] (and data on file) |
| Percentage of RSV-LRTD cases with resource usee | ||||
| Hospitalizationf |
Calibrated based on rates reported by McLaughlin et al. [6] with adjustment for medical attendance rate Range: calibrated based on rates reported by Herring et al. [26] and Branche et al. [30] |
|||
| 60–64 years | 3.0% | 1.9% | 4.7% | |
| 65–74 years | 10.7% | 4.7% | 16.6% | |
| 75–84 years | 14.3% | 7.1% | 22.2% | |
| ≥ 85 years | 14.3% | 12.1% | 22.2% | |
| ED visit | Calibrated based on rates reported by McLaughlin et al. [6] with adjustment for medical attendance rate | |||
| 60–64 years | 5.0% | – | – | |
| 65–74 years | 9.2% | – | – | |
| Outpatient visit | Calibrated based on rates reported by McLaughlin et al. [6] with adjustment for medical attendance rate | |||
| 60–64 years | 50.6% | – | – | |
| ≥ 65 years | 67.6% | – | – | |
| Antibiotic use | Calculated from Belongia et al. [27] with adjustment for medical attendance rate | |||
| 60–64 years | 44.6% | – | – | |
| ≥ 65 years | 59.6% | – | – | |
| Percentage of RSV-URTD cases with resource usee | ||||
| Outpatient visit | Calibrated based on rates reported by McLaughlin et al. [6] with adjustment for medical attendance rate | |||
| 60–64 years | 25.1% | |||
| ≥ 65 years | 33.6% | |||
| Antibiotic use | Calculated from Belongia et al. [27] with adjustment for medical attendance rate | |||
| 60–64 years | 18.4% | – | – | |
| ≥ 65 years | 24.6% | – | – | |
| Probability of death given RSV-LRTDg | Calculated from Tseng et al. [7] with adjustment for hospitalization rate | |||
| 60–64 years | 0.002166 | 0.001173 | 0.003159 | |
| 65–74 years | 0.007621 | 0.004126 | 0.011116 | |
| ≥ 75 years | 0.013467 | 0.009505 | 0.017430 | |
| Percentage of RSV-LRTD cases resulting in pneumoniah | Calculated from Belongia et al. [27] with adjustment for medical attendance rate | |||
| 60–64 years | 12.9% | – | – | |
| ≥ 65 years | 17.2% | – | – | |
Ranges reported were used in sensitivity analyses to evaluate the sensitivity of results to key model inputs.
ARI Acute respiratory illness; LRTD lower respiratory tract disease; N number; NREVSS National respiratory and enteric virus surveillance system; PCR polymerase chain reaction; RSV respiratory syncytial virus; URTD upper respiratory tract disease; US United States
aThe model accounted for all-cause mortality, derived from age-specific US 2020 annualized values for probability of death [22], converted to monthly probabilities. See additional data in Table S2
bSymptomatic RSV-ARI incidence was calculated as the average incidence of symptomatic RSV-ARI across four winter seasons from Falsey et al. [2], with weighting based on the proportions of non-high-risk and high-risk adults (66.3 and 33.7%, respectively) enrolled in a large influenza vaccine trial conducted in the US by DiazGranados et al. [23]. Lower and upper bounds were based on the minimum and maximum seasonal incidence of symptomatic RSV-ARI across the four winter seasons from Falsey et al. [2]
cSeasonality multipliers were calculated based on the total number of PCR-confirmed RSV detections each month from the National Respiratory and Enteric Virus Surveillance System RSV data (for 2018–2019) [25]. See additional details in Table S3
dThe percentage of symptomatic RSV-ARI cases that are RSV-LRTD was obtained from the placebo arm of the AReSVi-006 phase 3 clinical trial over two full seasons, where 139/292 RSV-ARI cases were classified as RSV-LRTD [20] (and data on file). Lower and upper bounds were based on 95% confidence intervals
eHealthcare resource use was based on age-specific rates of outpatient visits, ED visits, and hospitalizations (adjusted for underdetection) obtained from McLaughlin et al. [6], and antibiotic use obtained from Belongia et al. [27]. For outpatient visits, ED visits, and hospitalizations, the model used a calibration process to determine the respective model inputs. The data from McLaughlin et al. and Belongia et al. only included medically attended RSV cases. Therefore, to estimate the percentage of all symptomatic RSV cases with resource use (including both medically attended and nonmedically attended RSV cases), the resource use was adjusted by the percentage of symptomatic RSV cases that are medically attended (estimated from McLaughlin et al. [6] and Herring et al. [26])
fLower and upper bounds for the age-specific percentages of RSV-LRTD cases resulting in hospitalizations were based on the range of hospitalization rates observed in the literature. Specifically, the lower bound was based on the age-specific RSV-related hospitalization rates reported by Branche et al. (using the lowest RSV-related hospitalization rates reported from the study’s Rochester, New York site during the 2019–2020 RSV season) [30]. The upper bound was based on the upper limits of the modeled RSV-related hospitalization rate from Herring et al. [26]
gRSV-related mortality rates among LRTD cases were calculated based on the estimated percentage of RSV-LRTD cases that are medically attended (60–64 years: 50.6%; ≥ 65 years: 67.6%, derived from McLaughlin et al. [6] and Herring et al. [26]), the estimated age-specific hospitalization rates per medically attended RSV-LRTD case (60–64 years: 6.0%; 65–74 years: 15.8%; ≥ 75 years: 21.2%, derived from McLaughlin et al. [6]) and the estimated age-specific 30-day mortality following RSV-LRTD hospitalization (60–74 years: 7.1%; ≥ 75 years: 9.4%, derived from Tseng et al. [7]). Although age-specific 30-day mortality data were not reported by Tseng et al. [7] the study reported an overall in-hospital mortality rate of 5.6%, including 4.6% in individuals aged 60–74 years and 6.1% in individuals aged ≥ 75 years. The relative changes in the in-hospital mortality rates by age versus the overall in-hospital mortality rate were used to derive age-specific 30-day mortality. Lower and upper bounds were calculated based on the 95% confidence interval around the 30-day mortality post-hospitalization (60–74 years: 3.9–10.4%; ≥ 75 years: 6.6–12.2%). These rates were then applied to the age-specific percentages of RSV-LRTD cases resulting in hospitalization to generate overall RSV-LRTD mortality estimates
hBelongia et al. [27] provides the number of X-ray-confirmed pneumonia cases out of the total number of medically attended moderate to severe RSV-LRTD cases. Because these data include medically attended RSV cases, the percentage of LRTD cases resulting in pneumonia from Belongia et al. [27] was adjusted by the percentage of RSV-LRTD cases that are medically attended (estimated from McLaughlin et al. [6] and Herring et al. [26])