Health Impact Alternate Scenario 19 months Overview

Scenario		
Hospitalizations
Fatalities
Main Estimate  
277,736
6,830
19-Month Baseline 
144,720
3,559

This alternative 19-month baseline scenario uses an entirely different methodology to derive its estimates of hospitalizations and fatalities than the methodology used in the main analysis and the other alternative scenarios. While OSHA believes its main analysis is more relevant at this time, the alternative 19-month baseline methodology is much more closely aligned with the methodology that OSHA used in its Healthcare ETS published in June 2021, which relies on a historic average over roughly the same time period. 
 
The two main differences in the overall approach between the main 6-month analysis and this alternative 19-month analysis are summarized in the table below:

Comparison of key differences in baseline data between main and alternative estimates

Baseline number
Duration
Main Estimate
CDC # of cases and fatalities for unvaccinated persons (14 States) 
April 1, 2021 to September 4,, 2021
19-Month Baseline
CDC # of cases and fatalities for all persons (General Population)
March 1, 2020 to September 30, 2021

Additional differences in methodology flow necessarily from the reliance on these different baselines.  Both analyses require adjustments to focus the estimates on people within the working ages group of 18-64 and rely on essentially the same reductions to account for infections that might not be prevented by the ETS.

Methodology for Alternate Scenario 19 months
The description below is intended to provide a broad overview of the different steps necessary to arrive at the alternative estimates of the number of cases and fatalities prevented by this ETS.  The full calculations are contained in OSHA's Analytical Spreadsheets Supporting the Health Impacts of the COVID-19 Vaccination and Testing ETS (OSHA, October 28, 2021).

Step 1:  Estimate the number of cases and fatalities among the general population, aged 18 to 64 years old, over 19 months (March 1, 2020 to September 30, 2021)  
Starting point:  CDC data on expected number of COVID - 19 infections, hospitalizations, and fatalities prevented by the ETS is to identify the expected number of the respective health outcomes in the absence of the standard. OSHA adjusted the number of fatalities and cases upward to account for cases and fatalities where age was not identified.
Summary:  - Number of cases (adjusted) over 19 months, Ages 18-64 = 31,534,961
Number of fatalities (adjusted) over 19 months, Ages 18-64 = 151,219
         
Step 2:  Estimate the number of employees who will be vaccinated under the ETS.
This step, and its calculations, are identical to the first step in the main Health Impacts analysis.  As in that analysis, OSHA relied on the Cost Analysis Profile as starting point, which estimates that 20,822,580 employees will likely be vaccinated as a result of this ETS for Cost Purposes, and reduced that number to 18,914,528 for Impacts purposes.  Compared to the Cost Profile, this step removed from Impacts analysis the portion of the estimated 1.76 million Federal Contractors already required to be vaccinated by the Federal Contractor Guidance, as well as the portion of the population outside the 18-64 age group, who work for covered employers (those with 100 or more employees).  A reduction for health care workers covered by § 1910.502 is also accounted for in these calculations (see main analysis for details).   

Step 3:  Estimate infections avoided because of vaccinations under the ETS, ages 18-64, over 19 months 
OSHA calculated and then applied an infection rate for the general population over the 19 month baseline period (31,534,961 cases (Step 1)/196,957,000 (working population aged 18-64 (CPS, 2020)) = 16 percent), and then applied that rate to the number of workers likely to be vaccinated because of the ETS for Health Impacts purposes (Step 2).  This focuses the analysis only on those covered employees where vaccination under the ETS would be likely to prevent infection during the 19 month baseline period: 0.16 x 18,914,528 = 3,028,422 infections.  

Step 4:  Estimate fatalities avoided because of vaccinations under the ETS, ages 18-64, over 6 months  
OSHA estimated a Case-Fatality Ratio (151,219 fatalities (Step 1) / 31,534,961 cases (Step 1) = 0.005 fatalities per case), applied it to the infections avoided because of vaccinations under the ETS over 19 months (3,028,422 cases, Step 3), and, from that number, derived the fatalities avoided because of vaccinations under the ETS over 6 months.  OSHA also adjusted that number downward to account for 97% vaccine effectiveness, based on an Andrews study, as adjusted slightly upward to account for the removal of results from people in the age range of 65-74 (see Step 2).  OSHA also further adjusted that number downward to account for "community acquired infections" that would not have been prevented by this ETS by applying the same 20% percentage reduction as in Step 3A ("Derive adjusted cases") in the main Health Impacts analysis.  Finally OSHA adjusts for the time period of six months:  ((3,028,422 x 0.005 x 0.97 x 0.8)/19) x 6 = 3,559 fatalities.  

Step 5:  Estimate hospitalizations avoided because of vaccinations under the ETS, ages 18-64, in 6 months
To determine the number of hospitalizations, OSHA uses the same hospitalization rate formula as used in Step 4 of the main analysis (but using the number of fatalities in this analysis to generate the number of hospitalizations:  (3,559 fatalities / 0.024 ratio)  -  3,559 hospitalized fatalities = 144,720 hospitalizations.  For more information on this calculation and sources, see the main analysis.

References

Andrews et al. (2021, September 21). Vaccine effectiveness and duration of protection of Comirnaty, Vaxzevria and Spikevax against mild and severe COVID-19 in the UK. medRxiv preprint. doi:10.1101/2021.09.15.21263583. (Andrews et al., September 21, 2021) 
Centers for Disease Control (CDC) (2021, October 28) COVID-19 Cases and Deaths by State over Time. https://data.cdc.gov/Case-Surveillance/United-States-COVID-19-Cases-and-Deaths-by-State-o/9mfq-cb36. (CDC, October 28, 2021)
Centers for Disease Control (CDC) (2021, September 30). CDC's Cases and Deaths, Daily and Total Trends, found on the CDC COVID Data Tracker website (CDC Data Tracker) https://data.cdc.gov/Case-Surveillance/United-States-COVID-19-Cases-and-Deaths-by-State-o/9mfq-cb36. (CDC, September 30, 2021)
Occupational Safety and Health Administration (OSHA). (2021, October 28a). Analytical Spreadsheets Supporting the Health Impacts of the COVID-19 Vaccination and Testing ETS. (OSHA, October 28, 2021a)

