In 1997 the United States Centers for Disease Control published expert guidelines concerning the prevention of opportunistic infections.The guidelines were updated in November 2001.

Bacterial respiratory infections

Vaccination against pneumococcal pneumonia is recommended in all HIV-positive persons with CD4 counts above 200 who have not received this vaccination within the past five years. It is unknown how long this vaccine will provide protection in HIV-positive individuals. The response to this vaccine is likely to be weaker in people with CD4 counts below 200. In any case, Septrin protects against a broad spectrum of bacterial respiratory infections. However, re-vaccination is recommended if individuals had their first vaccination with a CD4 count below 200 and have subsequently experienced a CD4 increase on HAART.

In women diagnosed with HIV during pregnancy it may be advisable to defer vaccination until after anti-retroviral therapy has been commenced, owing to the possibility that vaccination-induced viraemia might increase the risk of vertical transmission.

In children under 5 years, Hib vaccine and pneumococcal conjugate vaccine should be administered; 23-polyvalent pneumococcal vaccine should also be given to children under the age of 2 with revaccination after 3-5 years.

The use of intravenous immune globulin should be considered in children with low gamma globulin levels (IgG < 400mg/dL), and in those with recurrent serious bacterial infections.

Cytomegalovirus

Prophylaxis may be considered in CMV-positive individuals with CD4 cell counts below 50 cells/mm³, using oral ganciclovir. However, there is no evidence that people who receive prophylaxis live longer, and the risk of side effects and interactions with other drugs is high. CMV prophylaxis is not routinely offered in the United Kingdom.

In those who have been diagnosed with active CMV disease, there are now a variety of maintenance options, but studies show that people who experience a sustained CD4 cell count increase above 100 to 150 cells/mm³ for at least six months may be able to stop maintenance treatment. Clinicians are advised to take into consideration the severity of any treated lesions, the extent of remaining vision, HIV viral load suppression and the feasibility of regular ophthalmic monitoring. Maintenance treatment should be resumed if the CD4 cell count subsequently falls below 100 cells/mm³.

Cryptococcosis

Prophylaxis may be considered in people with CD4 cell counts below 50 cells/mm³, but the risk of cryptococcosis must be weighed against the risk of developing resistance to anti-fungal drugs. Prophylaxis has not been shown to improve life expectancy, and the incidence of cryptococcosis is low in any case. However in individuals who have been successfully treated for cryptococcal disease, lifelong suppressive therapy with fluconazole is recommended. Prophylaxis may be discontinued in individuals after the CD4 cell count has risen above 100 to 200 cells/mm³ cells/mm³ for at least six months on antiretroviral therapy, and resumed if the CD4 cell count subsequently falls below this level.

Cryptosporidiosis

There is no known drug prophylaxis against cryptosporidiosis, and avoidance of water contaminated by cattle and livestock faeces is the best form of prevention. Avoiding contact with manure, animal faeces and human faeces is also recommended. Drinking water also carries a small risk of cryptosporidial contamination; boiling drinking water may offer protection.

Herpes simplex

Prophylaxis to prevent a first episode of herpes simplex is not recommended, and opinions vary as to whether initial episodes of herpes should be treated aggressively in HIV-positive people.

Maintenance treatment to prevent recurrence of herpes may be indicated in some individuals who experience frequent or severe recurrences; daily suppressive treatment with oral aciclovir or famiciclovir, or valaciclovir, is recommended.

Microsporidiosis

No known drug prophylaxis.

Mycobacterium avium intracellulare

US guidelines recommend prophylaxis against MAI in people with CD4 cell counts below 50 cells/mm³. Clarithromycin or azithromycin are the preferred prophylactic agents; a higher incidence of side effects is associated with the use of rifabutin. Primary prophylaxis may be discontinued after the CD4 cell count rises above 100 cells/mm³ for at least six months on antiretroviral therapy. Secondary prophylaxis can be stopped after the CD4 cell count has risen above 100 cells/mm³ for at least six months, providing that twelve months of MAI therapy have been completed. A negative culture for MAI may provide additional reassurance.

Prophylaxis in HIV-infected children is recommended in the first year of life if the CD4 cell count falls below 750 cells/mm³; in children aged one to two, below 500 cells/mm³; children aged two to six, 75 cells/mm³, and in children of six years or older, below 50 cells/mm³.

In the United Kingdom there is no consensus about MAI prophylaxis and many clinics do not routinely administer MAI prophylaxis.

Pneumocystis pneumonia

Prophylaxis should be offered to everyone with a CD4 cell count below 200 cells/mm³, or unexplained fever for more than two weeks, or a history of oropharyngeal candidiasis (thrush). Prophylaxis consists of one double-strength co-trimoxazole tablet a day. This drug is usually known by the brand name Septrin in the United Kingdom.

In children prophylaxis is recommended for all infants of HIV-infected mothers, regardless of whether HIV infection of the child has been confirmed. Prophylaxis should commence no later than four to six weeks after birth and should continue until HIV-negative status is confirmed. In HIV-positive children the need for prophylaxis should be reviewed after the first year of life, and discontinuation may be recommended if the CD4 cell count is above 500 cells/mm³ at this point.

In pregnant women PCP prophylaxis during the first trimester may be changed to aerosolised pentamidine if concerns exist about the possible effects of Septrin on the unborn child. However, there is no evidence that Septrin causes birth defects.

Primary prophylaxis may be safely discontinued in individuals with a sustained CD4 cell count increase above 200 cells/mm³ for at least three to six months.

Secondary prophylaxis (to prevent a recurrence) can be discontinued after a sustained CD4 cell increase above 200 cells/mm³ for at least six months. Prophylaxis should be resumed if the CD4 count subsequently falls below 200 cells/mm³.

Salmonellosis

Long-term therapy is recommended to prevent a recurrence in people diagnosed with salmonella. Ciprofloxacin is usually the first choice. It is unclear whether or not such treatment can be discontinued after a sustained CD4 increase on HAART.

Toxoplasmosis

Prophylaxis should be offered to everyone who is toxoplasmosis-positive with a CD4 count below 100. PCP prophylaxis using Septrin appears to offer protection against toxoplasmosis too. People with CD4 counts below 100 not taking Septrin should be tested on a regular basis for toxoplasmosis antibodies if previously negative.

Secondary prophylaxis in people who have been successfully treated for toxoplasmosis should consist of pyrimethamine, sulphadiazine and leucovorin to prevent relapse. It can be discontinued if the CD4 cell count increases above 200 cells/mm³ and is sustained for at least six months. Secondary prophylaxis should be resumed if the CD4 count subsequently falls below 200.

Tuberculosis

Tuberculosis exposure should be tested in anyone who is diagnosed HIV-positive, and anyone who is positive should undergo chest X-ray and clinical examination to eliminate the possibility of active tuberculosis. In the United States it is recommended that anyone with a positive result but no clinical evidence of tuberculosis should nevertheless receive nine months treatment with isoniazid as prophylaxis, or two months treatment with pyrazinamide and rifampin or rifabutin. Rifampin should not be administered with protease inhibitors or non-nucleoside reverse transcriptase inhibitors, with the exception of efavirenz, ritonavir/saquinavir, ritonavir and possibly nevirapine.

See Rifabutin in Drugs used by people with HIV: Antibiotic drugs for details of dose reduction recommendations when used with protease inhibitors or NNRTIs.

Tuberculosis exposure should be checked annually in those who test negative for TB on the first occasion.

Varicella zoster virus

For the prophylaxis of chickenpox, HIV-infected children and adults who are susceptible to VZV (i.e. those who have no history of chickenpox or shingles or no detectable antibody against VZV) should be administered VZV immune globulin within 96 hours after close contact with someone who has chickenpox or shingles.

Reference

Masur H et al. Guidelines for preventing opportunistic infections among HIV-infected persons - 2002. Recommendations of the US Public Health Service and the Infectious Diseases Society of America. Ann Intern Med 137: 435-478, 2002.