I'm not sure you've correctly interpreted that quote. most of participants who were aware [...] had been tested [...] in our lab. This does not preclude

I'm not sure you've correctly interpreted that quote. most of participants who were aware [...] had been tested [...] in our lab. This does not preclude any blood draws, in which the subject is tested, but not informed of results and infection status. They can test samples drawn expressly for the experiment, and not inform the individual, and then still use the lab-verified determination of infection status in the results. They can take blood, find out, and not tell the people if they are infected, even if they didn't know, and let them stay infected without knowing.