People will recall that iPrEx investigators questioned whether adherance to prophylaxis was the cause for transmissions in the active arm of the iPrEx study. Late Breaker #31LB reports on this. They compare plasma drug levels to those in an unrelated observed therapy trial STRAND with doing at 2, 4 and 7 days per week. The active arm had an overall preventative effect of 90% but when broken down by similarity to the STRAND data they found 76% efficacy at 2 day per week dosing levels, 96% at 4 and 99% at daily.
You will find the paper on the CROI Website, as well as the Oral Abstract session from 6 March 2012 in the 10am session.