Immunocompromised Travelers

Introduction

Immunocompromised people make up an estimated 6% of the U.S. population, and account for 1%–2% of patients seen in U.S. travel clinics. They may pursue itineraries similar to those of immunocompetent travelers. Pre-travel preparation for people with a suppressed immune status, whether due to a health condition, medication, or other treatment, is complex. During the pre-travel consult for an immunocompromised traveler, additional issues should be considered, including the patient's increased risk for both travel-associated and other infections and diseases, the effects travel may have on the patient's underlying condition, and the patient's response, adverse reactions to, or inability to receive pre-travel vaccines and travel medications. Key points to emphasize with immunocompromised travelers during a pre-travel visit are summarized in Box 2.2.1.

For more information on altered immunocompetence and vaccine administration, see General Best Practices for Immunization: Altered Immunocompetence.

Box 2.2.1

Pre-travel considerations

Guidance regarding travel-related prophylaxis and vaccination for immunocompromised individuals is less evidence-based than routine guidance for travelers; the recommendations included here are based on the best available data and the practices of experienced healthcare professionals.

Causes of immunosuppression

Healthcare professionals should recognize that different underlying conditions and treatments produce varying degrees of immunocompromise.

Consultation with other healthcare professionals

With permission, consider consulting with the traveler's primary or specialty care professional(s) to identify whether the underlying medical condition is stable, to discuss fitness for travel, and, when necessary, to verify medications and doses. Travel medicine specialists also can use such a consultation to evaluate whether any travel-related disease-prevention or treatment measures could destabilize the underlying medical condition, either directly or through drug interactions.

Contraindications and other health risks

Healthcare professionals should assess whether the traveler's conditions, medications, or treatments constitute contraindications to, decrease the effectiveness of, or increase the risk for adverse events from any of the disease-prevention measures recommended for the proposed trip. Depending on the destination, prevention measures might include immunizations or medications for malaria chemoprophylaxis or self-treatment for travelers' diarrhea. Healthcare professionals also should assess whether health hazards at the destination could exacerbate any underlying conditions or cause more severe health outcomes in an immunocompromised traveler and determine whether specific interventions are available to mitigate these risks.

Emergency planning

All international travelers should have contingency plans in the event they become ill overseas; this is an even more critical component of pre-travel preparation for immunocompromised travelers. An immunocompromised traveler should have a plan for when and how to seek care overseas, including a plan for medical evacuation, if necessary, and a plan for how to pay for it. They should be prepared to treat common infections they may have previously had (e.g., cellulitis, urinary tract infections, infectious diarrhea) with both medication(s) and instructions. They should travel with extra doses of regular medications, in case of travel delays, given that their health may be dependent on such medications (for more details, see Travel Insurance, Travel Health Insurance, and Medical Evacuation Insurance and What to Do When Sick Abroad chapters).

Immune status and vaccinations

Overall considerations for vaccine recommendations (e.g., destination, likely risk for exposure to disease) are the same for immunocompromised travelers as for other travelers. Healthcare professionals should weigh the risk for severe illness or death from a vaccine-preventable disease against potential adverse events, such as those from administering a live vaccine to an immunocompromised patient. It may not be safe for an immunocompromised traveler to receive live vaccines (e.g., yellow fever or measles vaccines), in which case the traveler should consider changing the itinerary, altering the planned travel activities, or deferring the trip. Knowledge of disease activity or endemicity (e.g., for measles, see CDC's Global Measles Outbreaks webpage; for yellow fever, see Yellow Fever and Yellow Fever Vaccine and Malaria Prevention Information, by Country chapters) may help guide decision-making. After careful consideration regarding risk versus benefit, some travelers may wish to accept the risk of disease at destination.

Approach to immunizations

Take a careful history and consider the nature of underlying diseases when preparing anyone for international travel. Keep in mind that not all medical conditions necessitate special considerations for pre-travel immunizations (Table 2.2.1). Recommend and provide all appropriate travel vaccines to those with chronic health conditions. Two categories of travelers requiring special consideration regarding immunizations are those with limited immune deficits and those with severe immune compromise. Vaccine recommendations for different categories of immunocompromised adults are listed in Table 2.2.2 and Table 2.2.3.

Table 2.2.1

Preparing travelers with limited immune deficits

Asplenia and complement deficiency/inhibitors

Asplenia is associated with varying degrees of immune deficit. For vaccination purposes, people with asplenia generally are not considered immunocompromised, and live vaccines are not contraindicated. People with anatomic or functional asplenia (including those with sickle cell disease or complement deficiency) and people taking eculizumab or ravulizumab (complement inhibitors used to treat paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome, and other diseases) are susceptible to overwhelming and rapidly progressive sepsis with certain bacterial pathogens, especially meningococcus, even with indicated immunizations.

Although response to vaccines might be diminished compared with people who have a functioning spleen, immunization against Haemophilus influenzae type b, meningococcal, and pneumococcal disease is recommended for patients with asplenia, regardless of travel plans. Because age-appropriate dosing and schedules for this population differ from immunocompetent hosts, consult the recommended immunization schedules at Immunization Schedules and the summaries in Table 2.2.2 and Table 2.2.3.

In addition to meningococcal vaccination, for those on complement inhibitors (and perhaps those with asplenia and comorbidities that increase the risk of infection or who are traveling to the meningitis belt), daily antibiotic prophylaxis with penicillin VK, ciprofloxacin, or azithromycin should be considered to avoid illness when traveling. For those with asplenia, travel with penicillin VK, ciprofloxacin, or azithromycin should be discussed in case they develop fever or other evidence of illness for initiation of self-treatment as a bridge while seeking health care. Risk is highest in the meningitis belt (see Meningococcal Disease chapter), but meningococcal disease could happen at any time. People with asplenia should consider avoiding travel to destinations lacking immediate access to high-standard medical care.

Table 2.2.2: Immunization of immunocompromised persons, live vaccines*

Table 2.2.3: Immunization of immunocompromised persons, non-live vaccines*^,†

Chronic diseases

Factors to consider when assessing the level of immune competence of patients with chronic diseases include clinical stability, comorbidities, complications, duration, severity, and any potentially immunosuppressing treatment (see Travelers with Chronic Illnesses chapter). The pre-travel health consultation is an opportunity to ensure that these individuals are vaccinated with recommended routine vaccinations (e.g., hepatitis B and pneumococcal vaccines) in addition to travel-related vaccines.

Hypogammaglobulinemia and intravenous immune globulin (IVIG) repletion

Many people with hypogammaglobulinemia or other indications receive periodic doses of intravenous immune globulin (IVIG), which can interfere with the immune response to measles, mumps, rubella (MMR) and varicella vaccine. If considering vaccination with MMR or varicella vaccine, administer the vaccine at least 14 days before the next scheduled IVIG dose. If they have recently received IVIG, there should be a delay of 8–11 months before they are given MMR or varicella vaccine (Table 3-6), rendering it challenging to give vaccine. IVIG may be adequate prophylaxis against measles and chickenpox for those who remain unvaccinated. Yellow fever (YF) vaccine can be administered at any time before or after or simultaneously with an antibody-containing product.

Multiple sclerosis

Inactivated non-live vaccines, including hepatitis A, hepatitis B, human papillomavirus, influenza, tetanus, meningococcal, pertussis, pneumococcal, injectable polio and typhoid, and recombinant zoster vaccines, can be safely used in patients with multiple sclerosis (MS) receiving or not receiving immunomodulatory therapy. In the event of a clinical relapse, however, vaccination should be delayed until patients have stabilized or have begun to improve, typically 4–6 weeks after the relapse began. mRNA COVID-19 vaccines are recommended for all patients with MS.

Modern MS therapy often includes early immunomodulatory therapy, which may preclude safe use of live vaccines. Live attenuated vaccines can be safely used in patients with MS not receiving immunomodulatory therapy or in those receiving interferons or glatiramer acetate (not considered immunosuppressive by MS expert consensus guidelines). Live viral vaccines (including YF) should be avoided in patients receiving the following therapies: dimethyl fumarate, ponesimod, siponimod, ozanimod, teriflunomide, natalizumab, cladribine, alemtuzumab, ocrelizumab, ofatumumab, or rituximab (see "Vaccine Considerations for Travelers with Severe Immune Compromise" section later in this chapter).

Yellow fever vaccine

A small case series published in 2011 reported worsening of MS symptoms and plaques in 5 of 7 patients with relapsing-remitting MS who received the YF vaccine. In contrast, 2 other studies (published in 2020 and 2021) identified no exacerbations among 55 people with MS who received the YF vaccine at different stages of their disease and who were taking a wide variety of medications. Vaccine-induced measles has been reported in a patient on natalizumab, suggesting a similar risk for other live viral vaccines. Before administering YF vaccine to people with MS who are receiving disease-modifying therapy or nataluzimab, consider the risk of YF virus infection at the destination, as well as potential vaccine-associated risks. Because the effects of YF vaccination in patients receiving disease-modifying therapy or nataluzimab have not been fully studied, decisions about YF vaccination should be made in consultation with the patient's neurologist. For brief exposures (e.g., only a few days in a YF endemic area), vaccinating travelers with MS against YF should be avoided, a YF vaccine waiver provided (Template Letter 2: Yellow Fever Vaccine Waiver), and insect avoidance should be emphasized. Weigh the risks and benefits of vaccination, with possible modification of MS treatment, for travelers anticipating more prolonged exposures.

Preparing travelers with moderate and severe immune compromise

Moderately and severely immunocompromising conditions

Factors to consider in assessing the general level of immune competence in a patient include disease severity, duration, clinical stability, complications, comorbidities, and any potentially immune-suppressing treatment. Definitions for moderate to severe immunocompromise appear in Box 2.2.2.

For additional information about the degree of immune suppression associated with different medical conditions and treatments, providers can consult ACIP's general best practices for vaccination of people with altered immunocompetence and the Infectious Diseases Society of America (IDSA) policy statement, 2013 IDSA Clinical Practice Guideline for Vaccination of the Immunocompromised Host.

In most cases, severely immunocompromised people should not receive live vaccines, and inactivated vaccines will likely be less effective. Patients with transient severe immunosuppression should consider postponing higher risk travel until their immune function improves. For people likely to travel in the future, travel-related vaccines can be initiated before beginning immunosuppressive therapies, if feasible. Whenever possible, administer inactivated vaccines ≥2 weeks and live vaccines ≥4 weeks before starting immunosuppression.

Box 2.2.2

Chronic lymphocytic leukemia and hematopoietic stem cell transplant

People with chronic lymphocytic leukemia have poor humoral immunity, even early in the disease course, and have a decreased response to vaccines. Hematopoietic stem cell transplant (HSCT) recipients who received vaccines before their transplant should be revaccinated routinely afterward, regardless of the source of the transplanted stem cells (autologous or allogeneic). Begin complete revaccination with standard childhood vaccines 6 months after HSCT, with the exception that MMR and varicella vaccines should be administered 24 months after transplant and only if the recipient is immunocompetent. Thus, HSCT recipients ideally should delay travel ≥2 years after transplant to allow for full revaccination with MMR and varicella vaccines.

Administer inactivated influenza vaccine beginning ≥6 months after HSCT and annually thereafter. A dose of inactivated influenza vaccine can be given ≥4 months after transplant if there is a community outbreak. COVID-19 vaccines have been shown to be immunogenic even shortly after HSCT and should be given routinely as per CDC guidance. Revaccination with COVID-19 vaccines should occur 3 months after HSCT. Administer 4 doses of PCV21 beginning 3–6 months after HSCT. The first 3 doses should be separated by 4 weeks and the fourth dose of PCV21 should be administered 6 months after the third dose or 1 year after the HSCT, whichever is later. For alternative PCV15-containing regimens, see Pneumococcal Vaccine for Adults Aged ≥19 Years: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023.

Solid organ transplant recipients

For solid organ transplant recipients, the risk for infection is greatest in the first year after transplant; recommend to travelers that they should postpone trips to high-risk destinations until after that time.

Medications that compromise the immune system

A variety of medications and biologic agents compromise the immune system. Per Box 2.2.2, persons who are moderate to severely immunocompromised include those on active treatment with high-dose corticosteroids (i.e., 20 mg or more of prednisone or equivalent per day when administered for 2 or more weeks), alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive, tumor necrosis factor blockers, and other biologic agents that are immunosuppressive or immunomodulatory (e.g., B-cell-depleting agents; for more information, see CDC's Altered Immunocompetence webpage). Live vaccines are contraindicated in these populations. B cell-depleting agents (e.g., cladribine, ocrelizumab, ofatumumab, ozanimod, rituximab, siponimod) and lymphocyte-depleting agents (e.g., alemtuzumab, thymoglobulin) induce major immunosuppression. Consideration of the clinical context in which these medications are given is important, as some diseases and comorbidities increase immunosuppression, as outlined in Box 2.2.2. Immunosuppressive or immunomodulatory biologic agents can produce immunocompromise by the mechanisms outlined in Table 2.2.4.

Doses of inactivated vaccines received while receiving immunosuppressive medications or during the 2 weeks before starting such medications should not be counted toward a primary vaccination series or relied upon to induce adequate immune responses. Patients should be revaccinated with all indicated inactivated vaccines at least 3 months after potent immunosuppressive therapy is discontinued.

Table 2.2.4: Immunosuppressive and immunomodulatory biologic agents that preclude use of live vaccines*

Cancer chemotherapeutic agents

Some 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., trastuzumab, given to patients with breast cancer, is 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 vaccines for 3–6 months after treatment or until they have had immune reconstitution.

High-dose corticosteroids

Most healthcare professionals consider a dose of 2 mg/kg or greater 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. Healthcare professionals should wait ≥1 month after discontinuation of high-dose systemic corticosteroid therapy before administering a live 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.

Vaccine considerations for travelers with severe immune compromise

Inform severely immunocompromised people that their response to vaccination might be suboptimal. 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 healthcare professionals 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 (e.g., 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.

Coronavirus disease 2019

U.S. COVID-19 vaccination guidance for moderately or severely immunocompromised people is updated often. The most recent guidance can be found at CDC's Interim Clinical Considerations for Use of COVID-19 Vaccines in the United States.

Cholera

The safety and effectiveness of the oral live attenuated replicating bacterial cholera vaccine, Vaxchora, has not been established in immunocompromised people. Caution is recommended when considering giving this to close contacts of immunocompromised people due to prolonged shedding and possible exposure (see Cholera chapter).

Ebola

Safety and efficacy of Ebola Zaire live replication-competent 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. Most travelers do not need this vaccine.

Hepatitis A

Data indicate that immunocompromised people, notably those being treated with immunosuppressive drugs, can have inadequate seroconversion after a single dose of hepatitis A vaccine (see Hepatitis A chapter). 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 hepatitis A should receive a 2-dose hepatitis A vaccine series. People with immunocompromising conditions should start a 2-dose hepatitis A vaccine series as soon as travel is considered. Testing for the presence of hepatitis A virus 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. Immunocompromised people traveling in <2 weeks should simultaneously receive the initial dose of hepatitis A vaccine and hepatitis A immune globulin (IG); administer the vaccine and the IG in separate limbs.

Hepatitis B

The humoral immune response to hepatitis B 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 given at least 1 month apart in people ≥18 years old. Post-vaccination serologic testing after any hepatitis B vaccination series is recommended to confirm response and guide the need for revaccination in immunocompromised people.

Japanese encephalitis

Although recommended for numerous destinations, no data are available on the safety or efficacy of Japanese encephalitis (JE) vaccines in immunocompromised patients (see Japanese Encephalitis chapter). 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

When possible, delay pre-exposure prophylaxis until a temporary immunocompromising condition has resolved or immunosuppressive medications can be withheld. For persons with ongoing immunosuppression, titers should be performed after primary vaccination. Check an antibody titer no sooner than 1 week (preferably 2–4 weeks) after pre-exposure (PrEP) dose 2; if the titer is less than 0.5 IU/mL, administer a booster dose and repeat titer check, but an antibody titer should be checked no sooner than 1 week (preferably 2–4 weeks) after completion of the 2-dose PrEP series and all booster doses, including those administered within 3 years of the primary series and in response to a low titer during the serial titer checks recommended for risk categories 1 and 2 (see Rabies chapter). If the titer is <0.5 IU/mL, a booster dose should be administered, followed by a subsequent titer check. If 2 such booster doses fail to elicit an acceptable antibody titer, persons without adequate titers should avoid high-risk activities.

For rabies post-exposure prophylaxis, immunocompromised persons who have had serologic confirmation of an adequate immune response to a prior PrEP or PEP regimen and who have not had clinically relevant changes that would alter their ability to respond to booster vaccination may receive a 2-dose booster vaccination series on days 0 and 3. Immunocompromised persons with a history of vaccination but no documentation of an adequate serological response, those previously vaccinated but with changes to their immune system that may negatively impact response to vaccination, and those without a history of prior vaccination should receive a full 5-dose vaccination regimen (days 0, 3, 7, 14, and 28) and rabies immune globulin. Regardless of the 2-dose or 5-dose PEP series administered, all patients with concern for an immune-compromising condition should undergo serologic confirmation no sooner than 1 week after completing the series. Many of these consultations will require case-by-case consultation by medical staff who are in the best position to deduce whether a patient may not respond adequately to a vaccination series. Immunocompromised travelers may experience difficulty accessing reliable post-vaccination serological testing services. In these situations, pursuing the 5-dose vaccination series with rabies immune globulin may be necessary; serological confirmation should be pursued once available.

Smallpox/mpox

JYNNEOS is a U.S. Food and Drug Administration (FDA)-approved live non-replicating smallpox/mpox vaccine that would not be contraindicated in immunocompromised individuals or their contacts when otherwise indicated.

ACAM2000 is a live, replicating smallpox/mpox vaccine indicated for use in military personnel and laboratory workers with potential exposure to the smallpox virus. Although it is not FDA approved for this purpose, it may protect against mpox. It is contraindicated for use in immunocompromised persons. Recipients of the vaccine can transmit the virus to household and intimate contacts; therefore, vaccinated family and household members should implement infection control measures, particularly those with immunocompromise.

Tick-borne encephalitis

Immunocompromised people might have a diminished immune response to killed tick-borne encephalitis vaccine, which is FDA approved and safe for immunocompromised persons. This vaccine should be administered as indicated based on risk of exposure (see Tick-Borne Encephalitis chapter).

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 (see Typhoid and Paratyphoid Fever chapter). 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 Yellow Fever chapter). 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 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 (also known as the "Yellow Card"; see Yellow Fever Vaccine and Malaria Prevention Information, by Country, Mosquitoes, Ticks, and Other Arthropods, and Yellow Fever chapters). 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. 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. If country entry requirements, and not true exposure risk, are the only reasons to vaccinate a traveler with a limited immune deficit, the physician should provide a waiver (see Yellow Fever and Template Letter 2: Yellow Fever Vaccine Waiver). For information about serologic testing, contact the state health department or CDC's Division of Vector-Borne Diseases at 970-221-6400.

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. 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 pre-travel indication exists, some travel clinics may encourage travelers to get this as per ACIP guidelines, especially if they are going on longer trips, to avoid getting shingles while traveling. 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.

Household contacts

Routine vaccines

Three live routine vaccines (MMR, rotavirus, and varicella) can 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. Although there are no reports of oral typhoid vaccine being administered to household contacts of an immunocompromised person subsequently resulting in disease transmission, some may wish to defer from using it in that setting.

For influenza vaccination, choose inactive influenza vaccine (IIV); household and other close contacts of mildly or moderately immunocompromised patients can safely receive the live attenuated influenza vaccine (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/mpox vaccine

JYNNEOS is an FDA-approved live non-replicating smallpox/mpox vaccine that would not be contraindicated in immunocompromised individuals or their contacts when indicated.

ACAM2000 is a live, replicating smallpox/mpox vaccine, indicated for use in military personnel and laboratory workers with potential exposure to the smallpox and mpox viruses. 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.

Yellow fever vaccine

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

Malaria prophylaxis and treatment

Asplenia and some immunosuppressive conditions and treatments can predispose travelers to more serious malaria infections. Furthermore, such patients may be more likely to experience drug interactions with malaria treatments (e.g., QT prolongation or altered mental status with tacrolimus and mefloquine). For these reasons, stress the need for malaria chemoprophylaxis and strict adherence to mosquito bite avoidance to immunocompromised travelers to malaria-endemic areas (see Yellow Fever Vaccine and Malaria Prevention Information, by Country, Mosquitoes, Ticks, and Other Arthropods, and Malaria chapters).

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 medications. Seek advice from CDC or other malaria experts when treating patients for malaria when needed. Increasing resistance to artemisinin drugs in both Asia and Africa means that immunocompromised persons with malaria treated with artemether/lumefantrine orally or artesunate IV need to be followed closely for recrudescence after initial clinical recovery.

Organ transplant recipients

In organ transplant recipients, atovaquone-proguanil is the favored malaria prophylactic agent because other antimalarials can interact with calcineurin inhibitors and mTor inhibitors (e.g., 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, and Shigella) can be severe or become chronic in immunocompromised people. Provide all travelers with instruction on safe water, food, and beverage precautions (see Food and Water Precautions for Travelers chapter); travelers' diarrhea can occur despite strict adherence. Meticulous adherence to clean drinking water, food precautions, and hand hygiene, including frequent and thorough handwashing with soap and water, is essential for the prevention of 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 requires special consideration of potential drug interactions in patients already taking medications for chronic medical conditions (see Travelers' Diarrhea chapter). Fluoroquinolones, rifaximin, and rifamycin SV are active against several enteric bacterial pathogens, although resistance is noted. 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, or 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 healthcare professionals 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 and inhaled fungal infections such as Talaromyces marneffei (formerly Penicillium marneffei) in Southeast Asia and coccidioidomycosis in the Americas (see Leishmaniasis chapter). Risk for COVID-19 and tuberculosis may occur in any country. 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.

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 SARS-CoV-2. Moreover, moderately or severely immunocompromised people may routinely shed infectious virus for a prolonged time (see COVID-19 chapter).

Counsel moderately and severely immunocompromised people to be up to date with their COVID-19 vaccinations before travel, including to get an extra dose of vaccine before travel if indicated. 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 pre-travel 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. SARS-CoV-2 spreads easily on cruise ships; outbreaks can overwhelm onboard medical capacity, and ship-to-shore medical evacuations can be challenging (see Cruise Ship Travel chapter).

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. In case they develop COVID-19 at destination, they should travel with COVID-19 test kits, and have a plan in place for seeking treatment. The oral treatment nirmatrelvir/ritonavir has significant drug interactions which may preclude safe use, and the other oral option, molnupiravir, may be less effective. Intravenous therapy with remdesivir may not be readily available. See the latest guidance and recommendations regarding COVID-19 vaccinations, boosters, and therapeutic options (Interim Clinical Considerations for COVID-19 Treatment in Outpatients).

Tuberculosis

Establishing the tuberculosis status of immunocompromised travelers going to regions endemic for tuberculosis can be helpful in the evaluation of subsequent illness (see Tuberculosis chapter). 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 gamma 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 post-travel testing (often 3 months after travel) depends on exposure risk during the trip, medical conditions, and other factors.