Cancer Chemotherapeutic Agents

Cancer chemotherapeutic agents are classified as severely immunosuppressive, as demonstrated by increased rates of opportunistic infections and blunting of responses to certain vaccines among patient groups. Some of these agents are less immunosuppressive than others (e.g., tamoxifen and trastuzumab, given to breast cancer patients, are less immunosuppressive than alkylating agents or antimetabolites), but clinical data to support safety with live vaccines are lacking. Vaccination following immunotherapies (e.g., checkpoint inhibitors, CAR-T cell treatments) has not been well studied, and until additional data are available, avoid vaccinating patients receiving these treatments with live attenuated vaccines for 3–6 months after treatment or until they have had immune reconstitution.

High-Dose Corticosteroids

Most clinicians consider a dose of >2 mg/kg of body weight or ≥20 mg per day of prednisone (or its 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 vaccines. Furthermore, the immune response to vaccines could be impaired. Clinicians should wait ≥1 month after discontinuation of high-dose systemic corticosteroid therapy before administering a live-virus vaccine.

Transplant-Related Immunosuppressive Drugs

Regard anyone receiving transplant-related immunosuppressive drugs as severely immunocompromised. Examples of transplant-related immunosuppressive drugs include azathioprine, belatacept, cyclosporine, everolimus, mycophenolate mofetil, prednisone, sirolimus, and tacrolimus.

Tumor Necrosis Factor Blockers

Tumor necrosis factor (TNF) blockers (e.g., adalimumab, certolizumab pegol, etanercept, golimumab, infliximab) blunt the immune response to certain chronic infections and certain vaccines. When used alone or in combination regimens with other disease-modifying agents to treat rheumatoid disease, TNF blockers are associated with an impaired response to HepA, influenza, and pneumococcal vaccines, suggesting that for better protection, all doses in the HepA and pneumococcal series should be given before travel. The use of live vaccines is contraindicated for most people receiving these therapies.

Vaccine Considerations for Travelers with Severe Immune Compromise

Inform severely immunocompromised people that their response to vaccination might be muted. The immunosuppressive regimen does not predict the decrease in response to vaccination. No basis exists for interpreting laboratory studies of general immune parameters to predict vaccine safety or efficacy. Recent data in solid organ transplant recipients vaccinated before transplant suggest that a prolonged phase of protective antibody titers can exist after transplant. In general, serologic testing for response to most travel-related vaccines is not clinically recommended.

The length of time clinicians should wait after discontinuation of immunosuppressive therapies before administering a live vaccine is not uniform and depends on the therapy. For cancer chemotherapy, radiation therapy, and highly immunosuppressive medications (exclusive of lymphocyte-depleting agents and organ transplant immunosuppression), the waiting period is 3 months. For lymphocyte-depleting agents (alemtuzumab, rituximab), the waiting period is ≥6 months, although IDSA guidelines suggest that the waiting period should be ≥1 year. For immunosuppressive corticosteroid regimens, the waiting period is 1 month. Restarting immunosuppression after live vaccination has not been studied, but some experts would recommend waiting ≥1 month. Special considerations for travelers with severe immune compromise apply for several travel-related vaccines.

Cholera

The safety and effectiveness of the oral live attenuated bacterial cholera vaccine, Vaxchora, has not been established in immunocompromised people. An older formulation of CVD 103-HgR vaccine was not associated with serious or systemic adverse events in patients with HIV, although the data are limited.

Ebola

Safety and efficacy of Ebola Zaire live recombinant vaccine (ERVEBO, rVSV-ZEBOV vaccine [Merck Sharp & Dohme Corp.]) has not been adequately assessed in immunocompromised adults. A small number of adults living with HIV have been vaccinated with ERVEBO, and additional studies are ongoing to investigate its use in people living with HIV without severe immune compromise. The risk from vaccination with ERVEBO in immunocompromised people should be weighed against the risk for Ebola virus disease.

Hepatitis A

Data indicate that immunocompromised people, notably those being treated with immunosuppressive drugs, can have inadequate or slow seroconversion after a single dose of HepA vaccine. Limited data also suggest that modified dosing regimens, including a doubling of the standard antigen dose or administration of additional doses prior to travel, might increase response rates.

Solid organ transplant candidates who are unvaccinated, undervaccinated, or seronegative for HepA should receive a 2-dose HepA vaccine series. People with immunocompromising conditions should start a 2-dose HepA vaccine series as soon as travel is considered. Immunocompromised people traveling in <2 weeks should simultaneously receive the initial dose of HepA vaccine and HepA immune globulin (IG); administer the vaccine and the IG in separate limbs. Testing for the presence of HAV antibody after vaccination is recommended for immunocompromised people whose subsequent clinical management depends on knowledge of their immune status and people for whom revaccination might be indicated. Because response to HepA vaccine might be reduced in people with HIV infection, perform postvaccination serologic testing on all people with HIV infection ≥1 month after they complete the HepA vaccine series.

Hepatitis B

The humoral immune response to HepB vaccine is reduced in immunocompromised children and adults. Limited data indicate that modified dosing regimens could increase response rates. As with dialysis patients, use a 3-dose series of 40 µg Recombivax HB at 0, 1, and 6 months, or a 4-dose series of 40 µg Engerix-B at 0, 1, 2, and 6 months. Heplisav-B (HepB-CpG) is an adjuvanted vaccine and is administered as 2 doses, 1 month apart, in people ≥18 years old. Postvaccination serologic testing after any HepB vaccination series is recommended to confirm response and guide the need for revaccination in immunocompromised people.

Japanese Encephalitis

Although recommended for numerous destinations (see Sec. 5, Part 2, Ch. 13, Japanese Encephalitis), no data are available on the safety or efficacy of Japanese encephalitis (JE) vaccines in immunocompromised patients. JE vaccine should be given to at-risk travelers. As with other vaccines, immunocompromised patients likely will have decreased intensity and durability of protection, and more frequent booster doses might be indicated.

Rabies

Immunocompromised people deemed at risk for vaccine-preventable rabies should receive a 3-dose series of vaccine on days 0, 7, and 21 or 28, but not the 2-dose series (day 0 and day 7) recommended in 2021 for immunocompetent people. Furthermore, administer the vaccine as an intramuscular injection, not as an intradermal injection as recommended by some authorities outside the United States. Serologic postvaccination testing might be indicated. For postexposure rabies prophylaxis, all severely immunocompromised people should generally receive rabies vaccine at days 0, 3, 7, 14, and 28, plus human rabies immune globulin, regardless of previous vaccination history.

Smallpox / Monkeypox

JYNNEOS (Imvamune, Imvanex) is an approved by the US Food and Drug Administration (FDA) vaccine for prevention of smallpox and monkeypox, but it is not commercially available. JYNNEOS is a live, attenuated, nonreplicating, virus-derived vaccine that is indicated for first responders participating in smallpox or monkeypox outbreaks. Unlike the live, replication-competent smallpox vaccine (ACAM2000), JYNNEOS is not contraindicated for use in immunocompromised people and should be safe. Immunocompromised people might, however, have a diminished immune response to the vaccine.

Tick-Borne Encephalitis

Immunocompromised people might have a diminished immune response to killed tick-borne encephalitis vaccine, which is FDA-approved and safe for this population.

Typhoid Fever

CDC recommends administering injectable Vi capsular polysaccharide vaccine (Typhim Vi, ViCPS) rather than live, oral Salmonella typhi vaccine Ty21A (Vivotif) for at-risk, immunocompromised patients. Data on the safety and efficacy of typhoid vaccines in immunocompromised patients are lacking.

Yellow Fever

Contraindications

In general, strongly discourage unvaccinated travelers with severe immune compromise from traveling to destinations where infection with YF virus is a risk. Severe immunosuppression is a contraindication to YF vaccination because these patients are at increased risk of developing a serious adverse event (e.g., life-threatening YF vaccine–associated viscerotropic disease, YF vaccine–associated neurologic disease). Additionally, YF vaccination is contraindicated in people with a history of a thymus disorder associated with abnormal immune cell function (e.g., myasthenia gravis or thymoma); this contraindication applies regardless of whether the person has undergone therapeutic thymectomy (see Sec. 5, Part 2, Ch. 26, Yellow Fever). No data are available to support IgA deficiency as a contraindication to YF vaccination.

If patients are unable to avoid travel to areas where YF vaccination is recommended (see Maps 5-10 and 5-11) and the immunocompromised traveler is previously unvaccinated, inform them of YF risk, carefully instruct them in methods to avoid mosquito bites, and provide them with a vaccination medical waiver in their International Certificate of Vaccination or Prophylaxis (see 

International Certificate of Vaccination or Prophylaxis, and Sec. 5, Part 2, Ch. 26, Yellow Fever). Travelers falling into this category might choose to travel during periods of lower disease activity. Warn travelers that some countries with YF vaccine entry requirements might not honor YF vaccination waiver documents and that the traveler might be refused entry or quarantined.

Precautions (Relative Contraindications)

ACIP considers certain conditions with limited immune deficits (e.g., asymptomatic HIV infection) to be precautions (as opposed to contraindications) to administration of YF vaccine. For these patients, offer YF vaccine if travel to YF-endemic areas is unavoidable, and monitor vaccine recipients closely for possible adverse effects. If country entry 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 (see /travel/page/icvp, and Sec. 5, Part 2, Ch. 26, Yellow Fever). Studies show that higher CD4+ T-lymphocyte counts and suppressed HIV viral loads seem to be the key determinants for developing protective neutralizing antibodies after YF vaccination. Patients with undetectable viral loads respond well to YF vaccination regardless of CD4+ T-lymphocyte counts, although data are limited in those with CD4+ T-lymphocyte counts <200/mL. Because vaccine response might be suboptimal, such vaccinees are candidates for serologic testing 1 month after vaccination. For information about serologic testing, contact the state health department or CDC’s Division of Vector-Borne Diseases at 970-221-6400. Current data from clinical and epidemiologic studies are insufficient to evaluate the actual risk for severe adverse effects associated with YF vaccine among recipients with limited immune deficits.

Booster Doses

Because a single dose of YF vaccine provides long-lasting protection, ACIP no longer recommends booster doses for most travelers. Additional doses of YF vaccine are recommended, however, for some people who might not have as robust or sustained immune response to YF vaccine.

People who received HSCT after receiving a dose of YF vaccine and who are sufficiently immunocompetent to be safely vaccinated should be revaccinated if travel puts them at risk for YF. People infected with HIV when they received their last dose of YF vaccine should receive a dose every 10 years if they continue to be at risk for YF and if their current CD4+ T-lymphocyte counts do not indicate precautions or contradictions. Recent data suggest that YF vaccination before solid organ transplant, even long before transplant, generally provides protective antibody levels after transplant.

Zoster

Although no extra pretravel indication exists, many travel clinics administer zoster vaccines. In 2021, the FDA approved the use of recombinant zoster vaccine (RZV), now the only available preparation in the United States, for all immunocompromised people ≥18 years of age.

ACIP recommends 2 doses of recombinant zoster vaccine for all adults ≥19 years old who are or who will be immunodeficient or immunosuppressed due to disease or therapy, regardless of travel plans. Qualifying underlying conditions include, but are not limited to, HSCT or solid organ transplant recipients, hematologic and or generalized cancer, HIV, and people receiving immunosuppressive therapy.

Household Contacts

Routine Vaccines

Three live vaccines (MMR, rotavirus, and varicella) should be administered to susceptible household contacts and other close contacts of immunocompromised patients when indicated. If a varicella vaccine recipient has a rash after vaccination, direct contact with susceptible household contacts with altered immunocompetence should be avoided until the rash resolves. Educate immunocompromised patients about the risk for fecal–oral transmission of poliovirus in countries where the oral polio vaccine is used, since there have been reports of reversion to wild type virus with associated clinical disease.

For influenza vaccination, choose inactive influenza vaccine (IIV); household and other close contacts of mildly or moderately immunocompromised patients can safely receive LAIV if they are unable to receive IIV. LAIV is contraindicated in close contacts and caregivers of severely immunocompromised people who require a protected environment.

Smallpox / Monkeypox Vaccine

ACAM2000 is a live, replicating smallpox vaccine, indicated for use in military personnel and laboratory workers with potential exposure to the virus. Recipients of the vaccine can transmit the virus to household and intimate contacts; therefore, vaccinated family or household members should implement infection control measures, particularly those with immunocompromise. JYNNEOS is an FDA-approved but not commercially available live nonreplicating smallpox/monkeypox vaccine that would not be contraindicated in immunocompromised individuals or their contacts.

Yellow Fever Vaccine

Yellow fever vaccine can be administered to household contacts when indicated.

Malaria Prophylaxis & Treatment

Malaria infection and the drugs used to treat it can exacerbate an immunocompromised traveler’s underlying condition. Moreover, asplenia, HIV, and some immunosuppressive regimens can predispose travelers to more serious malaria infection. For these reasons, stress the need for malaria prophylaxis and strict adherence to mosquito bite avoidance to immunocompromised travelers to malaria-endemic areas (see Sec. 2, Ch. 5, Yellow Fever Vaccine & Malaria Prevention Information, by Country; Sec. 4, Ch. 6, Mosquitoes, Ticks & Other Arthropods; and Sec. 5, Part 3, Ch. 16, Malaria).

People Infected with HIV

Malaria is more severe in people infected with HIV; malaria infection increases HIV viral load and could exacerbate disease progression. In addition, take extra care when researching potential drug interactions in people with HIV who are receiving antiretroviral therapy. The University of Liverpool offers an interactive web-based resource for assessing possible drug interactions (mobile application also is available).

Chemoprophylaxis

Some older maintenance regimens for HIV have been noted to interact with drugs used for malaria chemoprophylaxis. Notably, chloroquine, mefloquine, and primaquine can interact with older maintenance regimens for HIV, particularly those containing protease inhibitors (PIs). Efavirenz lowers serum levels of both atovaquone and proguanil, but no evidence suggests clinical failure of these agents when used concurrently. Efavirenz also potentially can increase the production of hemotoxic primaquine metabolites.

Most current first-line regimens for HIV (integrase and entry inhibitors) have few drug interactions. Commonly used integrase inhibitors (bicetegravir, cabotegravir, dolutegravir, elvitegravir, raltegravir), and nucleoside/nucleotide reverse transcriptase inhibitor (NRTI) combinations (brand names include Descovy-Tivicay, Truvada-Tivicay) have no known interactions with CDC-recommended malaria chemoprophylactic drugs; the cobicistat booster co-formulated with elvitegravir (Stribild, Genvoya) theoretically could increase mefloquine levels. The emtricitabine, rilpivirine, tenofovir alafenamide (TAF)/tenofovir disoproxil fumarate (TDF) combinations (Odefsey and Complera) similarly have no interactions with antimalarial drugs.

Treatment

Malaria treatment regimens, including artemisinin derivatives, quinine/quinidine, lumefantrine (part of the artemether/lumefantrine combination, Coartem), and atovaquone and proguanil potentially could have interactions with many non-nucleoside reverse transcriptase inhibitors (NNRTIs), PIs, and the CCR5 receptor antagonist, maraviroc. Seek advice from CDC or other malaria experts when treating patients for malaria who are also on antiretrovirals.

Organ Transplant Recipients

In organ transplant recipients, atovaquone-proguanil might be the most appropriate malaria prophylactic agent because other antimalarials can interact with calcineurin inhibitors and mTor inhibitors (cyclosporine, everolimus, sirolimus, tacrolimus). Chloroquine, doxycycline mefloquine, and primaquine can elevate calcineurin inhibitor levels. Chloroquine and mefloquine can interact with calcineurin inhibitors to prolong the QT interval. Some travel-related medications need to be dose-adjusted according to altered hepatic or renal function.

Enteric Infections

Many foodborne and waterborne infections (e.g., those caused by Campylobacter, Cryptosporidium, Giardia, Listeria, Salmonella, or Shigella) can be severe or become chronic in immunocompromised people. Provide all travelers with instruction on safe food and beverage precautions; travelers’ diarrhea can occur despite strict adherence. Meticulous hand hygiene, including frequent and thorough handwashing with soap and water, is the best prevention against gastroenteritis. Travelers should wash hands after contact with public surfaces, after any contact with animals or their living areas, and before preparing or eating food.

Travelers’ Diarrhea

Selecting antimicrobial drugs for appropriate self-treatment of travelers’ diarrhea (see Sec. 2, Ch. 6, Travelers’ Diarrhea) requires special consideration of potential drug interactions in patients already taking medications for chronic medical conditions. Fluoroquinolones, rifaximin, and rifamycin SV are active against several enteric bacterial pathogens and are not known to have major interactions with highly active antiretroviral therapy (HAART) drugs. Macrolide antibiotics can, however, interact with HAART drugs. Fluoroquinolones and azithromycin are generally well tolerated in combination with calcineurin inhibitors and mTor inhibitors, but in rare instances increase a prolonged QT interval (caution in those >500 ms).

Waterborne Diseases

To reduce the risk for cryptosporidiosis, giardiasis, and other waterborne infections, immunocompromised travelers should avoid swallowing water during swimming and other water-based recreational activities and should not swim in water that might be contaminated with sewage or animal waste. Travelers with liver disease should consider avoiding direct exposure to salt water because of the risk for Vibrio spp. exposure, and all immunocompromised people should avoid raw seafood. Patients and clinicians should be aware of the risk for infection or colonization with multidrug-resistant organisms during travel; remind immunosuppressed travelers who become ill to report recent travel to their doctors.

Reducing Risk for Other Diseases

Geographically focal infections that pose an increased risk for severe outcomes for immunocompromised people include visceral leishmaniasis (see Sec. 5, Part 3, Ch. 15, Visceral Leishmaniasis) and inhaled fungal infections such as Talaromyces marneffei (formerly Penicillium marneffei) in Southeast Asia, and coccidioidomycosis (see Sec. 5. Part 4, Ch. 1, Coccidioidomycosis / Valley Fever) and histoplasmosis (see Sec. 5, Part 4, Ch. 2, Histoplasmosis) in the Americas.

Coronavirus Disease 2019

People with immunocompromising conditions or who are on immunosuppressive therapy are at increased risk for severe illness, hospitalization, and death if infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19). Moreover, moderately or severely immunocompromised people might routinely shed infectious virus for ≤20 days (see Sec. 5, Part 2, Ch. 3, COVID-19).

Counsel moderately and severely immunocompromised people to be up to date with their COVID-19 vaccinations before travel. Because people who are immunocompromised might have a less robust immune response to COVID-19 vaccines, even those whose vaccinations are up to date should maintain awareness of the COVID-19 situation at their destination. In the pretravel consultation, discuss the possible options of reconsidering travel or delaying travel to destinations where COVID-19 transmission is currently high and risk for infection is greater.

CDC also provides COVID-19 cruise ship information. SARS-CoV-2 spreads easily on cruise ships; outbreaks can overwhelm onboard medical capacity, and ship-to-shore medical evacuations can be challenging (see Sec. 8, Ch. 6, Cruise Ship Travel).

In addition to helping ensure that moderately and severely immunocompromised travelers are up to date with their COVID-19 vaccinations, provide information on the importance of taking protective measures (e.g., wearing a well-fitting mask or respirator while in public indoor spaces, avoiding spending time in poorly ventilated indoor locations). Suggest to immunocompromised travelers that they also consider wearing a well-fitting mask or respirator when outdoors during sustained close contact with others. Advise close contacts (e.g., household members, caregivers) of immunocompromised people to adhere to the same precautions. See the latest guidance and recommendations regarding COVID-19 vaccinations, boosters, and therapeutic options.

Tuberculosis

Establishing the tuberculosis status of immunocompromised travelers going to regions endemic for tuberculosis can be helpful in the evaluation of subsequent illness (see Sec. 5, Part 1, Ch. 23, . . . perspectives: Testing Travelers for Mycobacterium tuberculosis Infection). Depending on the traveler’s degree of immune suppression, the baseline tuberculosis status might be assessed by a tuberculin skin test, Mycobacterium tuberculosis antigen–specific interferon-γ assay (i.e., QuantiFERON-TB Gold or T-SPOT TB, both generally more sensitive in immunocompromised patients than skin testing), or chest radiograph. The need for posttravel testing (often 3 months after travel) depends on exposure risk during the trip, medical conditions, and other factors.

People with HIV and transplant recipients might require primary or secondary prophylaxis for opportunistic infections (e.g., Mycobacterium, Pneumocystis, and Toxoplasma spp.). Adherence to all indicated prophylactic regimens should be confirmed before travel.

The following authors contributed to the previous version of this chapter: Camille Nelson Kotton, Andrew T. Kroger, David O. Freedman

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