The advent of highly active antiretroviral therapy (HAART) has altered the care and disease course of patients with human immunodeficiency virus (HIV) infection. Mortality and morbidity rates have decreased significantly, CD4 lymphocyte counts have increased in treated patients and the incidence of Pneumocystis carinii pneumonia (PCP) has declined dramatically. Because of the decreasing incidence of PCP, the occasional toxicity of prophylaxis (usually trimethoprim-sulfamethoxazole) and the large number of pills that ambulatory patients with HIV are required to take, many physicians have begun to cautiously discontinue PCP prophylaxis in patients who have good sustained immunologic and virologic responses to HAART. Yangco and associates evaluated whether discontinuing prophylaxis affected the incidence of PCP among HIV-infected patients whose CD4 counts were greater than 200 cells per mm³ (200 × 10⁹ per L).

Patient data from an ongoing dynamic cohort study called the HIV Outpatient Study (HOPS) were evaluated, and those whose CD4 counts had increased to more than 200 cells per mm³ after HAART were included in the analysis. A total of 491 patients was selected nonrandomly by their physicians to continue or discontinue prophylaxis. Of these, 146 discontinued PCP prophylaxis and were followed for a mean of 18.2 months, and 345 continued prophylaxis and were followed for a mean of 14 months. Demographic information and clinical, immunologic, and virologic characteristics of all patients were compared.

Neither PCP nor toxoplasmosis developed in either group. The incidence of other bacterial infections, including pneumonia, sinusitis, bronchitis and urinary tract infections, was somewhat lower in patients who discontinued prophylaxis, but the difference did not achieve statistical significance. Patients who discontinued prophylaxis had a significantly higher CD4 count, a longer period of time with a high CD4 count, a lower viral load and 400 or fewer copies of HIV-1 RNA per mL, a level considered “undetectable.”

The authors conclude that select patients who demonstrate sustained virologic, immunologic and clinical response to HAART may be candidates in whom PCP prophylaxis may be safely discontinued. Their CD4 levels were higher before and after therapy, they maintained such high levels for a longer period of time and they had significantly lower viral loads. In addition, the incidence of bacterial infection rates and toxoplasmosis did not increase in patients who discontinued prophylaxis. Further study with randomized, controlled clinical trials is appropriate to evaluate the long-term effect of this strategy.