I believe I have found the most important risk factor for COVID-19. The frequency of preexisting PF4 antibodies is estimated at 1.4% in normal, 4.5% in elderly, 4.8% in pregnant and 8.6% in diabetic subjects! THE DAMAGE DONE BY THE SPIKE PROTEIN TO THE ENDOTHELIUM MIMICS ACUTE CORONARY SYNDROME. THIS ACTIVATES THE IMMUNE RESPONSE TO PF4 AND EXPLAINS WHY HEPARIN MAKES THE CONDITION WORSE! 

To explain the preexistence of HIT antibodies, it was proposed that heparin-like molecules (glycosaminoglycans) on injured endothelium bind with PF4 to form complexes with which the antibodies react. Neoantigens appeared to cause conformational change of PF4 to induce the production of heterogenetic antibodies in the Ig subclass in the presence of heparin like molecules.. In ACS, a high level of PF4 associated with the activated platelets facilitates production of heparin on therapeutic heparin infusion [3] . HIT would be likely to develop in ACS patients with preexisting HIT antibodies. Also, HIT is known to be complicated by thrombosis in the presence of HIT antibodies. This study was carried out to clarify whether preexisting HIT antibodies can be used to predict the risk of thrombotic complications during or after cardiac intervention in ACS. 

SCREEN FOR PF4 ANTIBODIES BEFORE ANY TREATMENTS!

Referenced/Related Paper

Preexisting Antibodies to Platelet Factor 4- Heparin Complexes in Patients with Acute Coronary Syndrome Who Have No History of Heparin Exposure

https://www.karger.com/article/pdf/88543