Chapter 8Advising Travelers with Specific Needs

Elaine C. Jong, David O. Freedman

APPROACH TO THE IMMUNOCOMPROMISED TRAVELER

The pre-travel preparation of travelers with immune suppression due to any medical condition, drug, or treatment must address several categories of concern:

• Is the traveler’s underlying medical condition stable? The travel health provider may need to contact the traveler’s primary and specialty care providers (with the patient’s permission) to discuss the traveler’s fitness to travel, give specific medical advice for the proposed itinerary, and verify the drugs and doses composing the usual maintenance regimen.
• Do the conditions, medications, and treatments of the traveler constitute contraindications to or decrease the effectiveness of any of the disease-prevention measures recommended for the proposed trip? Depending on the destination, these measures include but are not limited to immunizations and drugs used for malaria chemoprophylaxis and management of travelers’ diarrhea.
• Could any of the disease-prevention measures recommended for the proposed trip destabilize the underlying medical condition, directly or through drug interactions?
• Are there specific health hazards at the destination that would exacerbate the underlying condition or be more severe in an immunocompromised traveler? If so, can specific interventions be recommended to mitigate these risks?

The traveler’s immune status is particularly relevant to immunizations. Overall considerations for vaccine recommendations, such as destination and the likely risk of exposure to disease, are the same for immunocompromised travelers as for other travelers, although the consequences of not administering an indicated vaccine may be more severe. In some complex cases when travelers cannot tolerate recommended immunizations or prophylaxis, the traveler should consider changing the itinerary, altering the activities planned during travel, or deferring the trip. For purposes of clinical assessment and approach to immunizations, immunocompromised travelers fall into 1 of 4 groups, based on mechanism and level of immune suppression. Vaccine recommendations for different categories of immunocompromised adults are shown in Table 8-01.

MEDICAL CONDITIONS WITHOUT SIGNIFICANT IMMUNOLOGIC COMPROMISE

With regard to travel immunizations, travelers whose health status places them in one of the following groups are not considered significantly immunocompromised and should be prepared as any other traveler, although the nature of the previous or underlying disease needs to be kept in mind.

1. Travelers receiving corticosteroid therapy under any of the following circumstances:
   • Short- or long-term daily or alternate-day therapy with <20 mg of prednisone or equivalent.
   • Long-term, alternate-day treatment with short-acting preparations.
   • Maintenance physiologic doses (replacement therapy).
   • Steroid inhalers.
   • Topical steroids (skin, ears, or eyes).
   • Intraarticular, bursal, or tendon injection of steroids.
   • If >1 month has passed since high-dose steroids (≥20 mg per day of prednisone or equivalent for >2 weeks) have been used. However, after short-term (<2 weeks) therapy with daily or alternate-day dosing of ≥20 mg of prednisone or equivalent, some experts will wait 2 weeks before administering measles vaccine.
2. HIV patients with >500/mm³ CD4 T lymphocytes.
3. Travelers with a history of cancer who received their last chemotherapy treatment ≥3 months previously and whose malignancy is in remission.
   • These recommendations refer primarily to corticosteroids; it remains unknown how long other drugs should be discontinued for optimal immunization.
   • When patients are on immunosuppressive medications (including tumor necrosis factor [TNF] blockers) for conditions other than hematologic malignancies and cancer, some clinicians suggest waiting only 1 month since a last dose of such medications before immunization.
4. Bone marrow transplant recipients who are >2 years posttransplant, not on immunosuppressive drugs, and without graft-versus-host disease.
5. Travelers with autoimmune disease (such as systemic lupus erythematosus, inflammatory bowel disease, rheumatoid arthritis, or multiple sclerosis [MS]) who are not being treated with immunosuppressive drugs, although definitive data are lacking. Decisions should be made on an individual basis by the clinician and traveler.
6. CDC advises following its usual guidelines for use of vaccines in MS patients who lack prior immunity and who are not experiencing an exacerbation of disease. This advice concurs with that of the National Multiple Sclerosis Society (www.nationalmssociety.org).

MEDICAL CONDITIONS AND TREATMENTS ASSOCIATED WITH LIMITED IMMUNE DEFICITS

Asymptomatic HIV Infection

Asymptomatic HIV-infected people with CD4 cell counts of 200–500/mm³ are considered to have limited immune deficits. CD4 counts increased by antiretroviral drugs, rather than nadir counts, should be used to categorize HIV-infected people. The exact time at which reconstituted lymphocytes are fully functional is not well defined. To achieve a maximal vaccine response with minimal risk, many clinicians advise a delay of 3 months after reconstitution, if possible, before immunizations are administered. While seroconversion rates and geometric mean titers of antibody in response to vaccines may be less than those measured in healthy controls, most vaccines can elicit seroprotective levels of antibody in most HIV-infected patients in this category.

Transient increases in HIV viral load, which return quickly to baseline, have been observed after administration of several different vaccines to HIV-infected people. The clinical significance of these increases is not known, but they do not preclude the use of any vaccine.

Multiple Sclerosis

The Multiple Sclerosis Council for Clinical Practice Guidelines, published in 2001, contain the clinical practice guidance on “Immunizations and Multiple Sclerosis.” The expert panel that developed this guidance used CDC recommendations as their foundation. Updated comments are posted on the National Multiple Sclerosis Society website (www.nationalmssociety.org).  People with MS who are having a serious relapse (exacerbation) interfering with the activities of daily living should defer immunization until 4–6 weeks after onset of the relapse.

Inactivated vaccines are generally considered safe for people with MS. Administration of tetanus, hepatitis B, or influenza vaccines does not appear to increase the short-term risk of relapses in people with MS. However, published studies are lacking on the safety and efficacy of other vaccines (such as those against pneumonia, meningitis, typhoid, polio, hepatitis A, human papilloma virus, and pertussis). Inactivated vaccines are theoretically safe for people being treated with an interferon medication, glatiramer acetate, mitoxantrone, or natalizumab, although efficacy data are lacking.

In the past, many practicing neurologists have strongly advised their MS patients against the use of live-virus vaccines at any time. Live-virus vaccines should not be given to people during therapy with immunosuppressants, such as mitoxantrone, azathioprine, methotrexate, or cyclophosphamide, or during chronic corticosteroid therapy. However, a few published studies suggest that measles, rubella, and varicella vaccines may be safe in people with MS if administered several weeks in advance of, or several weeks after, immunosuppressive therapy. Yellow fever vaccine and smallpox vaccine have not been studied in people with MS and should not be given unless there is a compelling reason to do so (such as unavoidable direct exposure) and there has been a consultation with the patient’s neurologist.

Other Chronic Conditions

Chronic medical conditions that may be associated with varying degrees of immune deficit include asplenia, chronic renal disease, chronic liver disease (including hepatitis C), diabetes mellitus, and complement deficiencies. Because no information is available regarding possible increased adverse events or decreased vaccine efficacy following administration of live, attenuated viral or bacterial antigen vaccines to patients with these diseases, caution should be used if considering the administration of live vaccines to such patients. Factors to consider in assessing the general level of immune competence of these patients include disease severity, duration, clinical stability, complications, and comorbidities.

A blunted response to hepatitis B vaccine has been reported in patients with chronic liver disease; a decreased response to hepatitis B vaccine has also been observed in patients with diabetes. Additional doses of hepatitis B vaccine beyond the primary 3-dose series may be necessary. Double-dose hepatitis B vaccine preparations are used to promote optimal immunization of people with chronic renal failure and other patients with absent or suboptimal response to standard hepatitis B vaccine doses. Adjuvanted hepatitis B candidate vaccines undergoing clinical trials appear to be more effective for immunization of liver transplant patients and patients with renal insufficiency.

Asplenic patients are susceptible to overwhelming sepsis with encapsulated bacterial pathogens. Although response to vaccines may be less than in people with a functioning spleen, many clinical guidelines recommend immunization against meningococcal, pneumococcal, and Haemophilus influenzae disease in these patients, regardless of travel plans.

• Limited data show that vaccine response in people who have had a splenectomy was more impaired if splenectomy was performed because of hematologic malignancy rather than for splenic trauma.
• The meningococcal A/C/Y/W-135 conjugate vaccine is indicated for both pediatric and adult populations at risk.
• Although the polysaccharide-protein conjugate vaccines against disease due to Streptococcus pneumoniae (PCV13) and H. influenzae type b (Hib conjugate vaccine) infections appear to elicit an increased immune response and duration of protection in vaccine recipients, there are few published clinical studies and there are no approved indications for use of these vaccines in adults at this time.

People with terminal complement deficiencies appear to have increased susceptibility to meningococcal infections and should be immunized against meningococcal disease.

Severe Immune Compromise (Non-HIV)

Severely immunocompromised people include those who have active leukemia or lymphoma, generalized malignancy, aplastic anemia, graft-versus-host disease, or congenital immunodeficiency; others in this category include people who have received recent radiation therapy, people who have had solid-organ or bone marrow transplants, within 2 years of transplantation, or transplant recipients who are still taking immunosuppressive drugs.

People with chronic lymphocytic leukemia have poor humoral immunity, even early in the disease course, and rarely respond to vaccines. Complete revaccination with standard childhood vaccines should begin 12 months after bone marrow transplantation. However, measles, mumps, and rubella (MMR) vaccine should be administered 24 months after transplant if the recipient is presumed to be immunocompetent. Influenza vaccine should be administered 6 months after transplant and annually thereafter.

For solid-organ transplants, the risk of infection is highest in the first year after transplant, so travel to high-risk destinations should be postponed until after that time. Vaccine doses received while concurrently receiving immunosuppressive therapy or during the 2 weeks before starting therapy are not considered valid. At least 3 months after therapy is discontinued, patients should be revaccinated with all vaccines that are still indicated. People taking any of the following categories of medications are considered severely immunocompromised:

• High-dose corticosteroids—Most clinicians consider a dose of either >2 mg/kg of body weight or ≥20 mg per day of prednisone or equivalent in people who weigh >10 kg, when administered for ≥2 weeks, as sufficiently immunosuppressive to raise concern about the safety of vaccination with live-virus vaccines. Furthermore, the immune response to vaccines may be impaired. Clinicians should wait ≥1 month after discontinuation of high-dose systemic corticosteroid therapy before administering a live-virus vaccine.
• Alkylating agents (such as cyclophosphamide)
• Antimetabolites (such as azathioprine, 6-mercaptopurine)
• Transplant-related immunosuppressive drugs (such as cyclosporine, tacrolimus, sirolimus, mycophenolate mofetil, and mitoxantrone)
• Cancer chemotherapeutic agents, excluding tamoxifen but including low-dose methotrexate weekly regimens, are classified as severely immunosuppressive, as evidenced by increased rates of opportunistic infections and blunting of responses to certain vaccines among patient groups. Limited studies show that methotrexate monotherapy had no effect on the response to influenza vaccine, but it did impair the response to pneumococcal vaccine.
• TNF blockers such as etanercept, rituximab, adalimumab, and infliximab blunt the immune response to certain vaccines and certain chronic infections. When used alone or in combination regimens with methotrexate to treat rheumatoid disease, TNF blockers were associated with an impaired response to influenza vaccine and to pneumococcal vaccine as well.
  • Despite measurable impairment of the immune response, postvaccination antibody titers were often sufficient to provide protection for most people; therefore, treatment with TNF blockers does not preclude immunization against influenza and pneumococcal disease.
  • Although the potential benefits of live-viral and live-bacterial vaccines in patients receiving TNF blockers need to be weighed carefully against potential risks, most clinicians would be reluctant to use vaccines such as yellow fever in this situation, as the safety of using live vaccines is unknown for these agents.

Severe Immune Compromise Due to Symptomatic HIV/AIDS

Knowledge of the HIV-infected traveler’s current CD4 T-lymphocyte count is necessary for pre-travel consultation. HIV-infected people with CD4 cell counts <200/mm³, history of an AIDS-defining illness, or clinical manifestations of symptomatic HIV are considered to have severe immunosuppression (see Chapter 3, HIV and AIDS) and should not receive live attenuated viral or bacterial vaccines because of the risk that the vaccine could cause serious systemic disease. The response to inactivated vaccines also will be suboptimal; thus, vaccine doses received by HIV-infected people while CD4 cell counts are <200/mm³ should be ignored, and the person should be revaccinated ≥3 months after immune reconstitution with antiretroviral therapy.

In newly diagnosed, treatment-naïve patients with CD4 cell counts <200/mm³, travel should be delayed pending reconstitution of CD4 cell counts with antiretroviral therapy. This delay will minimize risk of infection and avoid immune reconstitution illness during the travel.

Household Contacts

Household contacts of severely immunocompromised patients may be given live-virus vaccines such as yellow fever, MMR, or varicella vaccines but should not be given the live attenuated influenza vaccine.

SPECIAL CONSIDERATIONS FOR IMMUNOCOMPROMISED TRAVELERS

Yellow Fever Vaccine

Travelers with severe immune compromise should be strongly discouraged from travel to destinations that present a true risk for yellow fever (YF). If travel to an area where YF vaccine is recommended (see Maps 3-18 and 3-19) is unavoidable and the vaccine is not given, these travelers should be carefully instructed in methods to avoid mosquito bites and be provided with a vaccination medical waiver (see Chapter 3, Yellow Fever).

Patients with limited immune deficits or asymptomatic HIV going to YF-endemic areas may be offered YF vaccine and monitored closely for possible adverse effects. As vaccine response may be suboptimal, such vaccinees are candidates for serologic testing 1 month after vaccination. For information about serologic testing, contact your state health department or CDC’s Division of Vector-Borne Diseases at 970-221-6400. Data from clinical and epidemiologic studies are insufficient at this time to evaluate the actual risk of severe adverse effects associated with YF vaccine among recipients with limited immune deficits.

If international travel requirements, and not true exposure risk, are the only reasons to vaccinate a traveler with asymptomatic HIV-infection or a limited immune deficit, the physician should provide a waiver letter. Travelers should be warned that vaccination waiver documents may not be accepted by some countries; if the waiver is rejected, the option of deportation might be preferable to receipt of YF vaccine at the destination.

Malaria Chemoprophylaxis

Immunocompromised travelers to malaria-endemic areas should be prescribed appropriate drugs for malaria chemoprophylaxis and receive counseling about mosquito bite avoidance—the same as for immunocompetent travelers (see Chapter 3, Malaria). However, special concerns for immunocompromised travelers include any of the following possibilities:

• Drugs used for malaria chemoprophylaxis may interact with drugs in the traveler’s maintenance regimen.
• The underlying medical condition will predispose the immunocompromised traveler to more serious disease from malaria infection.
• A malaria infection and the drugs used to treat the malaria infection may exacerbate the underlying disease.

The severity of malaria is increased in HIV-infected people: malaria infection increases HIV viral load and thus may exacerbate disease progression. There is a lack of published data on the safety and efficacy of CDC-recommended antimalarial regimens in the HIV-infected traveler taking highly active antiretroviral therapy (HAART) while traveling to malaria-endemic areas. Table 8-02 gives some examples of potential interactions between drugs used for malaria chemoprophylaxis and those used in HAART regimens:

• Tetracyclines have no clinically significant interactions expected with the protease inhibitors and nonnucleoside reverse transcriptase inhibitors, so doxycycline might be a reasonable recommendation for malaria chemoprophylaxis in a traveler on HAART going to a malaria-endemic area.
• Atovaquone-proguanil might be a reasonable malaria chemoprophylaxis choice for a traveler whose HAART regimen includes nelfinavir (protease inhibitor) and nevirapine (nonnucleoside reverse transcriptase inhibitor). Atovaquone is not expected to have any significant interaction with common nucleoside reverse transcriptase inhibitors, although no data are available for proguanil.
• New classes of antiretroviral drugs include entry inhibitors and integrase inhibitors, and little data are available. Since new drugs and drug combinations for HIV treatment are under continuous development, clinicians are encouraged to review the most current information regarding possible drug interactions. An interactive web-based resource for checking on drug interactions involving HAART drugs is found at the University of Liverpool website (www.hiv-druginteractions.org).

Artemisinin combination therapy, consisting of 6 oral doses of artemether-lumefantrine taken over 3 days, is one of the recommended treatments for uncomplicated malaria due to Plasmodium falciparum. For severe malaria infections, intravenous artesunate is available in the United States through an investigational new drug protocol by CDC (see Chapter 3, Malaria). Limited data have raised concerns that parasite clearance of P. falciparum after therapy with artemisinins may be delayed in malaria patients coinfected with HIV compared with those who are HIV seronegative, raising the possibility that the host’s immunity affects the efficacy of antimalarial drug treatment. The use of quinidine (and by implication quinine) in patients taking nelfinavir or ritonavir is contraindicated because of potential cumulative cardiotoxicity. However, if a patient has severe and complicated malaria, there may be no choice. In these circumstances, as in others, quinidine should be used only with close monitoring. In addition, careful monitoring should accompany quinidine therapy in patients taking amprenavir, delavirdine, or the lopinavir-ritonavir combination. Although the clinical significance, if any, is not known, several protease inhibitors have been shown in laboratory testing to inhibit the growth of malaria parasites.

Some clinical case reports suggest that asplenic people may be at higher risk of acquisition and complications of malaria, so asplenic travelers to malaria areas should be counseled to adhere conscientiously to the malaria chemoprophylaxis regimen prescribed for them.

Enteric Infections

Many foodborne and waterborne infections, such as those caused by Salmonella, Campylobacter, Giardia, and Cryptosporidium, can be severe or become chronic in immunocompromised people. Enteroaggregative Escherichia coli is an emerging enteric pathogen causing persistent diarrhea among children, adults, and HIV-infected people.

Safe food and beverage precautions should be followed by all travelers, but travelers’ diarrhea can occur despite strict adherence. Selection of antimicrobials to be used for self-treatment of travelers’ diarrhea may require special consideration of potential drug interactions among patients already taking medications for chronic medical conditions. Fluoroquinolones and rifaximin are active against several enteric pathogens and are not known to have significant interactions with HAART drugs. However, macrolide antibiotics may have significant interactions with HAART drugs (Table 8-03). Emerging therapies for diarrhea in HIV/AIDS patients may involve probiotics such as Lactobacillus rhamnosus GR-1, L. reuteri RC-14, and others.

Waterborne infections might result from swallowing water during recreational activities. To reduce the risk for cryptosporidiosis and giardiasis, patients should avoid swallowing water during swimming and should not swim in water that might be contaminated (with sewage or animal waste, for example).

Attention to hand hygiene, including frequent and thorough handwashing, is the best prevention against gastroenteritis. Hands should be washed after contact with public surfaces and also after any contact with animals or their living areas.

Reducing Risk for Other Diseases

Geographically focal infections that pose an increased risk of severe outcome for immunocompromised people include visceral leishmaniasis and several fungal infections acquired by inhalation (such as Penicillium marneffei infection in Southeast Asia and coccidioidomycosis in the Americas). Many developing areas have high rates of tuberculosis (TB), and establishing the TB status of immunocompromised travelers going to such destinations may be helpful in the evaluation of any subsequent travel-associated illness. Depending on the traveler’s degree of immune suppression, the baseline TB status may be assessed by obtaining a tuberculin skin test, chest radiograph, or Mycobacterium tuberculosis antigen-specific interferon-β assay.

Patients with advanced HIV and transplant recipients frequently take either ­primary or secondary prophylaxis for one or more opportunistic infections (such as pneumocystis, mycobacteria, and toxoplasma). Complete adherence to all indicated regimens should be confirmed before travel (see Chapter 3, HIV and AIDS).

BIBLIOGRAPHY

1. Amenta M, Dalle Nogare ER, Colomba C, Prestileo TS, Di Lorenzo F, Fundaro S, et al. Intestinal protozoa in HIV-infected patients: effect of rifaximin in Cryptosporidium parvum and Blastocystis hominis infections. J Chemother. 1999 Oct;11(5):391–5.
2. Anukam KC, Osazuwa EO, Osadolor HB, Bruce AW, Reid G. Yogurt containing probiotic Lactobacillus rhamnosus GR-1 and L. reuteri RC-14 helps resolve moderate diarrhea and increases CD4 count in HIV/AIDS patients. J Clin Gastroenterol. 2008 Mar;42(3):239–43.
3. Beran J. Safety and immunogenicity of a new hepatitis B vaccine for the protection of patients with renal insufficiency including pre-haemodialysis and haemodialysis patients. Expert Opin Biol Ther. 2008 Feb;8(2):235–47.
4. Bhadelia N, Klotman M, Caplivski D. The HIV-positive traveler. Am J Med. 2007 Jul;120(7):574–80.
5. Boerbooms AM, Kerstens PJ, van Loenhout JW, Mulder J, van de Putte LB. Infections during low-dose methotrexate treatment in rheumatoid arthritis. Semin Arthritis Rheum. 1995 Jun;24(6):411–21.
6. Brezinschek HP, Hofstaetter T, Leeb BF, Haindl P, Graninger WB. Immunization of patients with rheumatoid arthritis with antitumor necrosis factor alpha therapy and methotrexate. Curr Opin Rheumatol. 2008 May;20(3):295–9.
7. Brinkman DM, Jol-van der Zijde CM, ten Dam MM, te Boekhorst PA, ten Cate R, Wulffraat NM, et al. Resetting the adaptive immune system after autologous stem cell transplantation: lessons from responses to vaccines. J Clin Immunol. 2007 Nov;27(6):647–58.
8. CDC. Recommendations of the Advisory Committee on Immunization Practices (ACIP): use of vaccines and immune globulins for persons with altered immunocompetence. MMWR Recomm Rep. 1993 Apr 9;42(RR-4):1–18.
9. CDC. Vaccination of persons with primary and secondary immune deficiencies. Washington, DC: Public Health Foundation; 2009. Available from: http://www.cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/A/immuno-table.pdf.
10. Cohen C, Karstaedt A, Frean J, Thomas J, Govender N, Prentice E, et al. Increased prevalence of severe malaria in HIV-infected adults in South Africa. Clin Infect Dis. 2005 Dec 1;41(11):1631–7.
11. De Sousa dos Santos S, Lopes MH, Simonsen V, Caiaffa Filho HH. Haemophilus influenzae type b immunization in adults infected with the human immunodeficiency virus. AIDS Res Hum Retroviruses. 2004 May;20(5):493–6.
12. Douvin C, Simon D, Charles MA, Deforges L, Bierling P, Lehner V, et al. Hepatitis B vaccination in diabetic patients. Randomized trial comparing recombinant vaccines containing and not containing pre-S2 antigen. Diabetes Care. 1997 Feb;20(2):148–51.
13. Duchini A, Goss JA, Karpen S, Pockros PJ. Vaccinations for adult solid-organ transplant recipients: current recommendations and protocols. Clin Microbiol Rev. 2003 Jul;16(3):357–64.
14. Eigenberger K, Sillaber C, Greitbauer M, Herkner H, Wolf H, Graninger W, et al. Antibody responses to pneumococcal and hemophilus vaccinations in splenectomized patients with hematological malignancies or trauma. Wien Klin Wochenschr. 2007;119(7-8):228–34.
15. Fomin I, Caspi D, Levy V, Varsano N, Shalev Y, Paran D, et al. Vaccination against influenza in rheumatoid arthritis: the effect of disease modifying drugs, including TNF alpha blockers. Ann Rheum Dis. 2006 Feb;65(2):191–4.
16. Furst DE, Breedveld FC, Kalden JR, Smolen JS, Burmester GR, Bijlsma JW, et al. Updated consensus statement on biological agents, specifically tumour necrosis factor {alpha} (TNF{alpha}) blocking agents and interleukin-1 receptor antagonist (IL-1ra), for the treatment of rheumatic diseases, 2005. Ann Rheum Dis. 2005 Nov;64 Suppl 4:iv2-14.
17. Geretti AM, Doyle T. Immunization for HIV-positive individuals. Curr Opin Infect Dis. 2010 Feb;23(1):32–8.
18. Huang DB, Mohanty A, DuPont HL, Okhuysen PC, Chiang T. A review of an emerging enteric pathogen: enteroaggregative Escherichia coli. J Med Microbiol. 2006 Oct;55(Pt 10):1303–11.
19. Kamya MR, Gasasira AF, Yeka A, Bakyaita N, Nsobya SL, Francis D, et al. Effect of HIV-1 infection on antimalarial treatment outcomes in Uganda: a population-based study. J Infect Dis. 2006 Jan 1;193(1):9–15.
20. Kapetanovic MC, Saxne T, Sjoholm A, Truedsson L, Jonsson G, Geborek P. Influence of methotrexate, TNF blockers and prednisolone on antibody responses to pneumococcal polysaccharide vaccine in patients with rheumatoid arthritis. Rheumatology (Oxford). 2006 Jan;45(1):106–11.
21. Kaplan JE, Masur H, Holmes KK. Guidelines for preventing opportunistic infections among HIV-infected persons—2002. Recommendations of the US Public Health Service and the Infectious Diseases Society of America. MMWR Recomm Rep. 2002 Jun 14;51(RR-8):1–52.
22. Kofidis T, Pethig K, Ruther G, Simon AR, Strueber M, Leyh R, et al. Traveling after heart transplantation. Clin Transplant. 2002 Aug;16(4):280–4.
23. Laurence JC. Hepatitis A and B immunizations of individuals infected with human immunodeficiency virus. Am J Med. 2005 Oct;118 Suppl 10A:75S–83S.
24. Matulis G, Juni P, Villiger PM, Gadola SD. Detection of latent tuberculosis in immunosuppressed patients with autoimmune diseases: performance of a Mycobacterium tuberculosis antigen-specific interferon gamma assay. Ann Rheum Dis. 2008 Jan;67(1):84–90.
25. Mishra LC, Bhattacharya A, Sharma M, Bhasin VK. HIV protease inhibitors, indinavir or nelfinavir, augment antimalarial action of artemisinin in vitro. Am J Trop Med Hyg. 2010 Jan;82(1):148–50.
26. Nevens F, Zuckerman JN, Burroughs AK, Jung MC, Bayas JM, Kallinowski B, et al. Immunogenicity and safety of an experimental adjuvanted hepatitis B candidate vaccine in liver transplant patients. Liver Transpl. 2006 Oct;12(10):1489–95.
27. Skinner-Adams TS, McCarthy JS, Gardiner DL, Andrews KT. HIV and malaria co-infection: interactions and consequences of chemotherapy. Trends Parasitol. 2008 Jun;24(6):264–71.