https://www.researchsquare.com/article/rs-940278/v1
“Within 6,239,465 participants who encountered the VHA in 2019, 162,363 participants who had a positive COVID-19 test between March 1, 2020 and January 15, 2021 were selected into the COVID-19 group,”
Looks like this was done mostly pre-vaccine.
Since the study was done at a VA hospital I think the previous COVID health status of the patients was probably not the best. This may be an assumption but I am under the impression that vets try to avoid care at a VA hospital unless absolutely needed. Such as in cases of some chronic condition.
Also keep in mind how hospitalization may be defined. These participants could very well have spent up to 24 hours in the ER being treated but not considered admitted if VA criteria is similar to that of Medicare.
It is also known that it is not uncommon for patients to develop cardiac problems following a bout with severe pneumonia. A correlation of pulmonary embolism and pneumonia has also been shown.
What this means is that preventative treatment that focuses on keeping the lungs healthy is very important. Guess what has not been emphasized? The very same.