Ask HN: How do I convince my employer to let me work from home?

I am 8 months post Autologous stem-cell transplant for treatment of Hodgkin's Lymphoma and as such, I am still immuno-suppressed. I am already extremely concerned about contracting COVID-19 since I am required to visit the hospital once every three weeks for post transplant treatment, and I know they're already under-equipped to handle the situation. I am a developer who could work from home, if my employer allowed. Unfortunately, my employer has taken the "wait until it's an issue" stance, and expects that employees use their PTO to cover any days we take off. Their current work from home stance is "it is not currently possible to allow all employees to work remotely" meaning that no employees can work remotely.

For the health and safety of myself and those around me, how can I convince my employer to allow me to work from home?