I wouldn’t want a subdermal sensor that could break loose and give me a stroke. There already is transdermal sensors for diabetes that stick to the skin and have tiny microneedles that cross the dermal barrier to sense blood sugar levels those same transdermal sensors could be configured with Igd or similar antigen detector arrays to sense an active covid infection without having to implant a sensor full time. With modern thermoelectrics the sensors patch could even be powered by the bodies heat itself. Same effect much less risk. The patches are moved in diabetic patients every 14 days to a new location to allow the natural skin process of shedding and renewals.
I see no need for this government health censor to be sub-dermal. Perhaps shape it as a cameo brooch for formal female wear, or as an addition to the Apple watch?