Secondary (acquired) immunodeficiency due to medical conditions

• Generally, people with secondary immunodeficiency due to medical conditions can receive non-live vaccines according to routine immunisation schedules. But their response may be suboptimal and they may need extra doses.
• Most live vaccines are contraindicated in people with severe secondary immunodeficiency due to medical conditions. Exceptions are monovalent varicella and MMR (measles-mumps-rubella) vaccines which may be considered in transplant recipients who are clinically well, and on minimal immunosuppressive therapy (at least 1 year after solid organ transplant, or 2 years after haematopoietic stem cell transplant).

Secondary immunodeficiency due to medical conditions incorporates a complex and heterogeneous spectrum of immunocompromise. Immunodeficiency may occur due to:

• malignancies
• solid organ transplant
• stem cell transplant or cellular therapies such as haematopoietic stem cell transplant (HSCT) or chimeric antigen receptor modified T-cell (CAR-T) therapies
• certain infectious diseases such as HIV
• splenic dysfunction (see People with asplenia and hyposplenia)
• medical therapies (see Secondary (acquired) immunodeficiency due to medical therapies)

For more details about the immunosuppressive potential of various medications and medical conditions, see:

• Table. Types of medical conditions and immunosuppressive therapy and associated levels of immunocompromise
• Table. Immunosuppressive potential of cancer and organ rejection therapies
• Table. Immunosuppressive potential of conventional (non-biological) immunosuppressive therapies
• Table. Immunosuppressive potential of small molecule targeted therapies
• Table. Immunosuppressive potential of biological therapies
• Table. Immunosuppressive potential of corticosteroids
• Table. Immunosuppressive potential of certain medical conditions

People with secondary immunodeficiencies can safely receive non-live vaccines according to routine immunisation schedules, but responses may be suboptimal.

When feasible, all indicated non-live vaccines should be given at least 2 weeks before any planned period of immunosuppression.

Additional doses and altered schedules of certain non-live vaccines (such as COVID-19, influenza, pneumococcal, meningococcal, herpes zoster, hepatitis A, hepatitis B and HPV [human papillomavirus] vaccines) should be considered for this population, depending on the underlying immunocompromising condition. See the relevant disease-specific chapters for details, as well as:

• Table. Recommendations for vaccination in people who have received chemotherapy
• Table. Recommendations for vaccination before and after solid organ transplant
• Table. Accelerated immunisation schedule for infants, children and adults likely to require solid organ transplant
• Table. Recommendations for vaccination after haematopoietic stem cell transplant in children and adults
• Table. Recommendations for vaccination in children and adults with HIV

Live vaccines are generally contraindicated in people with severe secondary immunodeficiency, due to the risk of disseminated vaccine disease.

If indicated, live vaccines must be given at least 4 weeks before a planned period of severe immunosuppression.

If a period of (severe) immunosuppression due to a medical condition is temporary, revaccination or booster doses of live vaccines (such as MMR, varicella) are recommended for seronegative people after disease remission, when immune competence is demonstrated. However, recommendations vary depending on the person’s age, vaccination history, underlying condition, immunosuppressive treatment received and other comorbidities.

Malignant disorders include haematological malignancies and solid tumours. The risks of vaccine-preventable diseases and the effectiveness of vaccination vary in people with malignancies, depending on the disease stage and degree of immunosuppression. Patients with haematological malignancies tend to be more immunocompromised than those with solid tumours. However, patients with solid tumours may be at risk of infection due to their compromised health or anatomic obstruction. Most malignant disorders are treated with chemotherapy, radiotherapy or immunotherapy, which may cause immunosuppression as a side effect.

Non-live vaccines

Generally, people diagnosed with a malignancy can receive non-live vaccines. However, to optimise the immune response, consider delaying vaccination (if the risk of exposure to the pathogen is low) until the person is less immunocompromised.

Additional doses or booster doses of vaccines may be needed. For more details, see Vaccination after chemotherapy.

Live vaccines

Generally, live vaccines are contraindicated in people with immunodeficiency due to malignancies or cancer treatments, especially in people undergoing B- or T-cell-targeting biological therapies, immunosuppressive chemotherapy or radiotherapy.

Where indicated, live vaccines may be administered at least 4 weeks before planned immunosuppressive treatment for a solid tumour, if the treating specialist is confident that the underlying malignancy is not primarily immunosuppressive (and live vaccine administration is therefore considered to be safe).

In general, live vaccines may be administered when:

• a malignancy is in remission, and
• immune competence is demonstrated (such as lymphocyte count >1 × 10⁹/L), and
• immunosuppressive chemotherapy, immunotherapy or radiotherapy have not been administered for at least 3 months, and
• no anti-B-cell therapies (such as rituximab) have been administered in the past 6 months

For more details related to immunosuppressive cancer treatments, see Table. Recommended timing of live vaccine administration for people receiving immunosuppressive therapies

Vaccination before and during chemotherapy

When feasible, all indicated vaccines should be administered before starting treatment with chemotherapy:

• Live vaccines should be administered ≥4 weeks before starting chemotherapy.
• Non-live vaccines should be administered ≥2 weeks before starting chemotherapy.

Generally, vaccines are withheld during chemotherapy because the person is not able to mount an effective immune response, and to reduce the risks associated with live vaccine administration.

The exceptions are influenza and COVID-19 vaccines, which should be administered during treatment to protect against seasonal disease. Where possible, vaccines should be given immediately before a chemotherapy cycle.^1,2

People with neutropenia should avoid receiving vaccines during periods of severe neutropenia (absolute neutrophil cell count <0.5 × 10⁹/L). Although neutropenia is not an absolute contraindication to vaccination, this will help to minimise potential febrile episodes that may result in unnecessary investigations and empirical antibiotic treatments.

Vaccination after chemotherapy

Generally, people who have completed chemotherapy are recommended to receive additional doses of certain vaccines (such as COVID-19, diphtheria-tetanus-pertussis, pneumococcal) when the malignancy is in remission, and chemotherapy was completed at least 3 months previously.

The recommended vaccination schedules after chemotherapy may vary by person, depending on their age, vaccination history, the type of cancer, other immunosuppressive treatments received and other comorbidities. Consult the treating oncologist if uncertain.

People who have recently received blood products or immunoglobulin may also have further considerations around revaccination timing. See Vaccination for people who have recently received normal human immunoglobulin and other blood products.

Suggested primary and booster dose schedules for people who have completed chemotherapy are summarised in Table. Recommendations for vaccination in people who have received chemotherapy.

Solid organ transplant recipients are at increased risk of many vaccine-preventable diseases, including pneumococcal disease, influenza and varicella.³ People who have received or are planning to receive a solid organ transplant are eligible to receive additional vaccines.

Vaccination before solid organ transplant

If time permits, careful consideration should be given to the person’s pre-transplant immunisation status. Vaccines are more immunogenic if administered before transplant, because immunosuppressive medications given after transplant to prevent or treat organ rejection may diminish vaccine responses. However, vaccine responses may also be diminished in people with organ failure before transplant.

Non-live vaccines

Non-live vaccines should be administered at least 2 weeks before solid organ transplant, where possible, such as an annual influenza vaccine (see relevant disease-specific chapters).

Additional vaccines (such as hepatitis A, hepatitis B, HPV, herpes zoster and pneumococcal vaccines) may be recommended for certain groups of solid organ transplant candidates. See Table. Recommendations for vaccination before and after solid organ transplant for more details.

Live vaccines

Live vaccines should be administered at least 4 weeks before solid organ transplant, as these vaccines will generally be contraindicated after transplant.

MMR and varicella vaccine should be administered at least 4 weeks before transplant in seronegative children and adults (see Table. Recommendations for vaccination before and after solid organ transplant).

BCG vaccine should not be given to people who are anticipated to need an organ transplant in the future, unless the potential benefit outweighs the risk of disease reactivation after transplant (see Tuberculosis). If indicated, BCG vaccine should be given at least 4 weeks before transplant, provided the person is not severely immunocompromised at that time.

For infants requiring imminent solid organ transplant (such as infants born with congenital kidney or liver disease requiring transplant), see Table. Accelerated immunisation schedule for infants, children and adults likely to require solid organ transplant.

Where possible, living donors should receive all routinely scheduled vaccines before organ donation, and live vaccines should not be administered less than 4 weeks before organ procurement.

Vaccination after solid organ transplant

Solid organ transplant recipients generally need lifelong immunosuppression. The degree of immunosuppression varies substantially depending on the organ transplanted.

Usually, immunosuppression is greatest in the first 3–6 months after transplant, and progresses to a maintenance phase between 6 months and 1 year after transplant.^4,5 However, this timeline varies if the person needs treatment for organ rejection. The agent and dose of immunosuppressive medication to prevent or treat organ rejection may influence the effectiveness and safety of vaccines.

Some transplant recipients experience chronic rejection or persistent organ dysfunction, and may remain profoundly immunocompromised.³ See Secondary (acquired) immunodeficiency due to medical therapies for more details about safe vaccination for these people.

Non-live vaccines

Solid organ transplant recipients can safely receive non-live vaccines. To maximise the immune response to vaccination, non-live vaccines should ideally be given after immunosuppression has reached maintenance dosing. This is generally 3–6 months after transplant.

Solid organ transplant recipients should complete any missed doses for all indicated vaccines, as well as additional or booster doses. See Table. Recommendations for vaccination before and after solid organ transplant for a full list of recommended vaccines for solid organ transplant recipients. Also note some specific recommendations:

• Additional doses of COVID-19 and pneumococcal vaccines are recommended after solid organ transplant.
• Hepatitis A vaccine is recommended for certain seronegative solid organ transplant recipients (such as those with chronic liver disease or who had a liver transplant).
• HPV vaccine should be administered using a 3-dose schedule, regardless of age when they started vaccination.

Live vaccines

Live vaccines are generally contraindicated in most people after solid organ transplant because of the risk of disseminated infection. However, this is based on limited published data.^4,6,7

MMR and monovalent varicella vaccines may be considered at least 1 year after solid organ transplant following a risk–benefit assessment including the level of immunocompromise.^8,9 Alternatively, passive immunisation (with immunoglobulin) after exposure to measles or chickenpox should be considered if the transplant recipient is seronegative, or if their serological status for measles or varicella is unknown. See Passive immunisation.

MMRV (measles-mumps-rubella-varicella) vaccine is not recommended for people who have received a solid organ transplant because there are no data relating to the safety or efficacy of MMRV vaccine in this group.

If solid organ transplant recipients anticipate travelling to an area with a high risk of vaccine-preventable disease (such as endemic hepatitis A or typhoid risk), additional travel vaccinations are recommended. Seek specialist input about the safety of vaccination with live vaccines. See Vaccination for international travellers and Travellers who are immunocompromised).

Haematopoietic stem cell transplant (HSCT) involves the transplant of stem cells (sourced from bone marrow, peripheral blood or umbilical cord blood) after conditioning with chemotherapy, radiotherapy or both. HSCT recipients receive either their own cells (autologous HSCT) or cells from a donor (allogeneic HSCT).

Almost all HSCT recipients experience a prolonged period of immunosuppression after transplant, due to a combination of:

• the underlying condition requiring transplant (usually a malignancy, but may be a severe combined immunodeficiency)
• ablative or non-ablative conditioning received before transplant
• immunosuppressive therapy prescribed to prevent graft-versus-host disease (GVHD) after transplant
• the clinical impact of GVHD, if this occurs

The duration of immunosuppression after HSCT varies depending on the type of transplant received (allogeneic or autologous), stem cell source and manipulation, and the presence or absence of post-transplant complications.

Autologous HSCT recipients often have impaired immunity due to pre-transplant conditioning. Immune cell recovery can take several months to a year.^11,12

Allogeneic HSCT recipients experience profound immunosuppression after transplant. Immune cell recovery can take 1–2 years.¹¹

Efficacy data for vaccines administered to HSCT recipients are limited.^13-16 In general, lymphocytes that can respond to new antigens (presented in vaccines) are generated 6–12 months after transplant. This may occur slightly earlier in young children, and later in adults.^17,18

Based on limited published data, the same vaccination schedule is generally recommended for both autologous and allogeneic HSCT recipients, regardless of the donor source or the conditioning received before transplant (chemotherapy, radiotherapy or immunotherapy).^15,19,20

Vaccination before haematopoietic stem cell transplant

HSCT candidates should be carefully assessed before transplant and receive all routine scheduled vaccines where possible. Vaccination could be deferred until after transplantation in people with severe primary immunodeficiencies such as severe combined immunodeficiency or complete DiGeorge that may require the corrective stem cell transplant in early childhood. However, passive immunisation with an RSV-specific monoclonal antibody should not be delayed for infants with these conditions.

Non-live vaccines

All indicated routine non-live vaccines should be administered ≥2 weeks before the onset of the pre-transplant conditioning regimen, if possible.

Where time permits, a dose of PPV (pneumococcal polysaccharide vaccine) should be given after any previously administered PCV (pneumococcal conjugate vaccine), with a minimum interval of 2 months. See Pneumococcal disease.

Live vaccines

Live vaccines that are not contraindicated should be administered ≥4 weeks before the start of pre-transplant conditioning.

However, where possible, BCG (bacille Calmette–Guérin) vaccine should not be given at any time to people who may require HSCT, due to a theoretical risk of disease reactivation after transplant.

For vaccine-preventable diseases that have a defined correlate of protection, pre-transplant serology should also be assessed.

Donor vaccination may improve the HSCT recipient’s response to some vaccines.²¹ However, due to logistical and ethical issues, this is often not feasible. 

Vaccination after haematopoietic stem cell transplant

HSCT recipients should be considered as ‘never immunised’. They require complete re-immunisation after HSCT. This is because the ablation of haematopoietic cells in the bone marrow before transplant eliminates most (or all) immune memory.

In general, HSCT recipients should receive vaccines at a time when the immune response can be maximised. This timing should take into account the person’s immune recovery status and ongoing treatment with immunosuppressive therapy (see Secondary (acquired) immunodeficiency due to medical therapies).

Non-live vaccines

HSCT recipients should receive all routine non-live vaccines (or repeated doses) from 6 to 12 months after transplant. See Table. Recommendations for vaccination after haematopoietic stem cell transplant in children and adults and relevant disease-specific chapters.

Influenza and COVID-19 vaccines

HSCT recipients should receive a full primary course of influenza (2 doses in the first year after HSCT) and COVID-19 (2-3 doses based on individual risk assessment) vaccines as early as 3–6 months after HSCT.^22,23 Earlier administration of influenza vaccine can be considered if there is a seasonal outbreak, although the vaccine response may be less robust.

Exacerbation of GVHD has been reported in allogeneic HSCT recipients after they received COVID-19 mRNA vaccines, but causality is not yet confirmed.^24-27 Given the increased risk of COVID-19-associated morbidity and mortality in HSCT recipients, the benefits of vaccination are considered to outweigh the risks.²⁸

Pneumococcal vaccines

Pneumococcal conjugate (re)vaccination can start as early as 3–6 months after HSCT. HSCT recipients without chronic GVHD that requires immunosuppressants should receive 3 primary doses of PCV, followed by 2 doses of PPV (5 years apart).^29,30 If a person receives a dose of 21vPCV for their primary doses of PCV, subsequent doses of 23vPPV are not required.

GVHD is a risk factor for loss of immunity to pneumococcus.³¹ PPV also has lower immunogenicity in HSCT recipients with GVHD.³² If the HSCT recipient has moderate to active GVHD, a booster dose of PCV (instead of PPV) may be given after the last primary dose of PCV. This booster dose would not be required if the person received 3 primary doses of 21vPCV.

Low uptake of pneumococcal vaccination has been frequently reported in immunocompromised populations, which poses a concern about completing all recommended doses.^33,34 Providers may consider earlier administration of PPV in people who received a PCV schedule before HSCT. Alternatively, they may consider 21vPCV for the PCV schedule as the subsequent doses of PPV would not be required.

Other non-live vaccines

The following schedules of other non-live vaccines are also recommended after HSCT:

• A 3-dose schedule of diphtheria-tetanus-pertussis-polio containing vaccines is recommended.
• A 3-dose schedule of Haemophilus influenzae type b (hib) vaccine is recommended
• A 3-dose schedule of HPV vaccine is recommended for all HSCT recipients aged >9 years.
• A 3-dose schedule of hepatitis B vaccine (high-dose formulation, such as H-B-Vax II dialysis formulation) is recommended after HSCT.
• A 2-dose schedule of recombinant herpes zoster vaccine (Shingrix) is recommended for HSCT recipients aged >18 years.
• Primary and booster courses of MenACWY (meningococcal ACWY) and MenB (meningococcal B) vaccines are recommended for HSCT recipients according to age-appropriate dosing schedules.
• A single dose of RSV (respiratory syncytial virus) vaccine or RSV-specific monoclonal antibody is recommended for HSCT recipients according to age.

Live vaccines

Live vaccines are generally contraindicated in HSCT recipients until ≥24 months after transplant.

MMR and monovalent varicella vaccines may be considered ≥24 months after HSCT, but only when:

• there is no evidence of chronic GVHD, and
• immunosuppressive therapy has been discontinued for at least 3 months, and
• the person is deemed immunocompetent by their treating specialist

Based on emerging evidence suggesting some preserved immunity to measles and rubella in adult HSCT recipients,^35-38 serological testing for measles and rubella can be considered before MMR (re)vaccination from 24 months after HSCT. However, pre-vaccination serological testing may be less informative in children. Lack of access to serological testing should not restrict revaccination in adult patients.

If pre-vaccination measles and rubella immunity has not been confirmed, check serology after the 2nd dose to confirm seroconversion.

BCG vaccine should not be readministered after HSCT. The need for administering other live vaccines (if non-live vaccine options are not available, such as yellow fever and Q fever vaccines) should be considered on an individual basis, if future disease exposure is likely.

See Vaccination for international travellers and Travellers who are immunocompromised for more detail.

Chimeric antigen receptor modified T-cell (CAR-T) therapies involve reprogramming and enhancing a patient’s own T-cells to identify and eliminate malignant cells.⁴¹

CAR-T therapy has been used to treat haematological malignancies, especially those of B-cell origin. Most patients are immunosuppressed before CAR-T infusion due to the effects of their malignancy and previous cytotoxic treatments.

CAR-T therapy eliminates both malignant and normal cells that express the target antigen. This results in profound and prolonged loss of B-lymphocytes and antibody production. The extent of this can vary depending on the target antigen:

• CD19-targeted CAR-T therapy may not affect terminally differentiated B-cells (such as plasma cells, which have low CD19 expression). This may minimise the impact on established humoral immunity.⁴²
• B-cell maturation antigen (BCMA)-targeted CAR-T therapy depletes all BCMA-expressing plasma cells, leading to a profound and lasting humoral immune deficiency.⁴³

Vaccination before CAR-T therapy

Non-live vaccines

If indicated, non-live vaccines should be given ≥2 weeks before the onset of the pre-CAR-T conditioning regimens, where possible. But because the immune response may be suboptimal, non-live vaccines may need to be repeated after treatment and when immune competence is restored.

Live vaccines

Live vaccines are usually contraindicated before, during and immediately after CAR-T therapy. This is because of the underlying malignancy for which CAR-T therapy is indicated.

If indicated, live vaccines should be given ≥4 weeks before the onset of the pre-CAR-T conditioning regimens, where possible.

Vaccination after CAR-T therapy

Non-live vaccines

Generally, non-live vaccine administration may start 6–12 months after CAR-T therapy in patients with demonstrated immune reconstitution who are not receiving immunosuppressive or cytotoxic therapy.⁴⁴

Influenza and COVID-19 vaccination can start from 3 months after CAR-T therapy, irrespective of immunological reconstitution, although the vaccine response might be lower.

Re-immunisation with routine vaccines or other additional vaccinations should be considered to prevent or reduce the severity of vaccine-preventable diseases. For people who have had CAR-T therapy, follow the vaccination timing outlined in Table. Recommendations for vaccination after haematopoietic stem cell transplant in children and adults or seek specialist advice.

Live vaccines

Live vaccines may be considered after 24 months after CAR-T infusion, for patients who are in remission and do not require additional chemotherapy.

This recommendation is extrapolated from studies of vaccine responses in patients treated with rituximab, an anti-CD20 monoclonal antibody, alongside the kinetics of immune reconstitution after CD19-targeted CAR-T therapy.^45-47

IVIg and vaccination

CAR-T therapy recipients often receive intravenous immunoglobulin (IVIg) due to B-cell aplasia. This may alter the timing of catch-up vaccination. See Vaccination for people who have recently received normal human immunoglobulin and other blood products.

Immune recovery (described in some studies as CD4⁺, CD19⁺ or CD20⁺ cell counts >200 cells/μL)⁴⁴ usually occurs 9–12 months after CAR-T therapy.^43,47,48 However, the impact of CAR-T therapy on previously established (memory) humoral immunity is unknown, and terminally differentiated CD19-negative plasma cells may confer long-term pathogen-specific immunity.⁴⁹

For people who have recently received IVIg, follow the vaccination timing outlined in Vaccination for people who have recently received normal human immunoglobulin and other blood products.

HIV infects CD4⁺ T-cells. Without antiretroviral treatment, this can result in a progressive decline in CD4⁺ cell count, increasing vulnerability to infection and suboptimal responses to vaccines.

The CD4⁺ cell count and degree of immunosuppression in people with HIV relate to the disease stage and response to antiretroviral therapy. The level of immunocompromise is estimated by a recent CD4⁺ count or CD4⁺ percentage, or both. See Table. Levels of immunocompromise in children and adults with HIV.

People with HIV should receive vaccines based on their:

• age
• CD4⁺ count
• risk of exposure to vaccine-preventable diseases (for example, if they are planning travel)
• presence or absence of concurrent medical conditions or medications (which may be further immunocompromising)

People with HIV, of any age, whose disease is well controlled are likely to respond well to vaccines. HIV is usually considered to be well controlled when the person:

• is taking a combination of antiretroviral therapy
• has an undetectable or low viral load
• has an adequate CD4⁺ lymphocyte count (see Table. Levels of immunocompromise in children and adults with HIV)

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