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COVID-19 Resources

General Principles of COVID-19 Vaccines for Immunocompromised Patients

(Version 3.0; last updated April 5, 2021)

Input from Jeff Auletta, MD; Roy Chemaly, MD; Roy Chemaly, MD; Fareed Khawaja, MD; Genovefa Papanicolaou, MD; Josh Hill, MD; Julie Kanter, MD; Alpana Waghmare, MD; Adrian Wiestner, MD; John Wingard, MD; and Laura C. Michaelis, MD.

Please see specific FAQ for guidance on vaccination in patients who have received HCT or CAR T cells.

In the United States, two novel messenger RNA (mRNA) vaccines and one novel adenovirus vector- based vaccine have been approved through the U.S. Food and Drug Administration’s (FDA’s) Emergency Use Authorization (EUAs; Table). The BNT162b2 (Pfizer/BioNTech) and the mRNA-1273 (Moderna) COVID-19 vaccines have both been shown in large phase III clinical trials to be more than 90 percent effective at preventing lab-confirmed COVID-19 illness and severe infections.1,2 The single-dose recombinant, replication-incompetent adenovirus serotype 26 vector-based vaccine (Ad26.COV2.S; Johnson& Johnson/Janssen) reduced the incidence of symptomatic COVID-19 with a reported overall efficacy of 66.1 percent (72% in the United States) based on data from the phase III clinical trial. The overall lower efficacy was thought to be due to the newly emerging SARS-CoV-2 variant arising from South Africa (20H/501Y.V2 variant [B.1.351]), which was the predominant strain circulating in South Africa at the time of the clinical trial and accounted for 95 percent of the sequenced isolates.

Table. List of currently approved COVID-19 vaccines under Emergency Use Authorization in the United States

Platform Vaccine Manufacturing Company Age Limit (years) Number of Doses/Intervals (weeks)
mRNA BNT162b2 Pfizer and BioNTech ≥ 16 2 doses/ 3 weeks apart
mRNA mRNA-1273 Moderna ≥ 18 2 doses/ 4 weeks apart
Recombinant adenovirus vector Ad26.COV2.S Johnson & Johnson/Janssen ≥ 18 1 dose

What are mechanisms of action for the leading candidate SARS-CoV-2 vaccines?

Leading SARS-CoV-2 vaccine candidates use either conventional or novel mechanisms of action to elicit an immune response in patients. Conventional methods include administration of attenuated inactivated (killed) virus3 or recombinant viral protein3 vaccines to develop immunity. Novel approaches include replication-deficient, adenovirus vector-based vaccines that contains the SARS-CoV-2 spike protein5,6 and mRNA-based vaccines that encode for a SARS-CoV-2 spike protein.7,8 Based on phase I/II studies, candidate SARS-CoV-2 vaccines elicited both humoral and cellular immune responses.

How are the SARS-CoV-2 vaccines administered and what challenges exist for vaccination?

All except one of the vaccine candidates being tested require two separate inoculations separated by three to four weeks. Current challenges for an approved SARS-CoV-2 vaccine include manufacture to scale, distribution, storage conditions, reconstitution, and administration, particularly for the lipid nanoparticle mRNA-based vaccines, which require low temperatures for adequate vaccine preservation. Most importantly, the public must be willing to receive the vaccine.

What SARS-CoV-2 vaccines are approved for use in immunocompromised patients?

Despite several vaccine candidates being in phase II/III clinical trials, no current clinical trial of a COVID-19 vaccine has published data on immunocompromised patients. Thus, the efficacy and safety of a SARS-CoV-2 vaccine has not been established in the different immunocompromised patient populations. There are no data that preferentially support one vaccine over another in this or any population.

Why might some hematology patients not respond to vaccines?

In order to generate optimal protective immunity following vaccination, intact host immunity is needed, particularly with respect to antigen presentation, B- and T-cell activation, and plasma B cell antibody generation. Therefore, hosts lacking functional adaptive immune cells may be unable to generate a fully protective immune response to a SARS-CoV-2 vaccine approved for use in the general population.

The following immunocompromised patient populations could have attenuated or absent response to SARS-CoV-2 vaccines:

  1. Primary a. Primary and secondary immunodeficiencies involving adaptive immunity
  2. Splenectomy or functional asplenia [e.g., sickle cell disease]
  3. B cell directed therapies (e.g., blocking monoclonal antibodies against CD20 or CD22, bispecific agents like blinatumomab, CD19 or CD22-directed chimeric antigen receptor T cell [CAR-T] therapies, Bruton tyrosine kinase [BTK] inhibitors)
  4. T-cell-directed therapies (e.g., calcineurin inhibitors, antithymocyte globulin, alemtuzumab)
  5. Many chemotherapy regimens
  6. High-dose corticosteroids (≥20 mg per dose or >2 mg/kg/day daily prednisone or equivalent)
  7. Hematopoietic cell transplantation (HCT), especially within the first three to six months after autologous HCT and often longer after allogeneic HCT
  8. Underlying aberrant immunity (e.g., graft-vs.-host disease, graft rejection, absent or incomplete immune reconstitution, neutropenia ANC <500/μL, lymphopenia ALC <200/μL)

What is known about the safety and efficacy of protein-based or killed (inactivated virus) vaccines in immunocompromised patients?

Vaccine safety encompasses acute and long-term adverse effects associated with a vaccine. Based on experience with other recombinant protein-based and inactivated (killed) virus-based vaccines, no major adverse effects or unique adverse effects have been reported in immunocompromised patients.9 Common acute adverse effects associated with candidate SARS-CoV-2 vaccines reported to date include low-grade fever, myalgias, headache, nausea, fatigue and soreness/redness at the injection site. These acute adverse effects were more pronounced after the booster dose (2nd vaccine dose) in some of the trials. Long-term adverse effects have not been defined for SARS-CoV-2 vaccines and will be available once phase III trials have completed long term follow up in healthy volunteers. Initial data on safety will be available for at least two months from vaccine administration based on EUA minimum standards. A national monitoring system exists for reporting vaccine-related adverse events.

The efficacy of protein-based or inactivated (killed) SARS-CoV-2 vaccines in immunocompromised patients has yet to be studied. Prior experience with inactivated or killed virus vaccines have demonstrated some efficacy in immunocompromised patients, leading some societies to recommend vaccination of this population.10 Vaccine responses are influenced by the underlying disease and the type and timing of recent therapy. The adjuvanted recombinant (protein-based) zoster vaccine was safe and elicited robust humoral and cellular immune responses across patients with hematologic malignancies when administered during or up to six months after immunosuppressive therapy. However, response rates in patients with chronic lymphocytic leukemia (CLL) or non-Hodgkin lymphomas, many likely treated with anti-CD20 containing regimens, were lower than in the rest of the hematologic malignancies.11,12

Flu vaccines using killed virus are safe and can elicit humoral immune responses in immunocompromised patients, but response rates appear to be highly variable, reported between 15 and 63 percent of CLL patients not actively treated, and in 7 to 26 percent in patients on BTK inhibitor (ibrutinib) therapy.

The immune response to varicella zoster is a memory response, as the vast majority of people have formed antibodies against varicella zoster virus in childhood. Similarly, response to influenza is, at least in part, a memory response. In contrast, response to SARS-CoV-2 will require a de novo immune response and much less is known about how well immunocompromised patients will be able to generate such a response.

Potential considerations for testing prior to administration of SARS-CoV-2 vaccine in an immunocompromised patient include complete blood count with differential, peripheral blood B- and T-cell immunophenotype, quantitative immunoglobulins (IgG, IgM, IgA), and tetanus and pneumococcal titers, to determine if a patient is likely to mount a protective immune response. The impact of these parameters on responses to SARS-CoV-2 vaccines is unknown.

What is known about the safety and efficacy of attenuated live vaccines in immunocompromised patients?

Live attenuated vaccines carry the risk of converting to pathogenic strains with particular risk in immunocompromised patients. It is unclear if a live attenuated SARS-COV-2 vaccine will have the same major risk, but due to the theoretical concerns, a live vaccine should be avoided in immunocompromised patients. Another potential risk from live-attenuated vaccines in general is the possible transmission of the virus to close contacts of the vaccines. The only live SARS-CoV-2 vaccines are in production in India and Turkey.

Although there are no data for mRNA/DNA and using other viruses to deliver vaccines, what are the theoretical considerations in immunocompromised patients?

mRNA/DNA-based and virus vector-based (usually adenovirus) vaccines have been previously proposed with some application for cancer treatment. Theoretical concerns for their use include a hyper-inflammatory response, which was described in some animal models who received adenovirus vector vaccines.10 This effect has not been demonstrated in humans. Another concern is the development of autoimmune syndromes related to the increased type I interferon response elicited by an mRNA/DNA vaccine.13

Given patients with chronic lymphocytic leukemia, lymphoma or myelodysplasia and patients after allogeneic hematopoietic cell transplantation may be prone to other immune-mediated complications, there is some concern that generating anti-SARS-CoV-2 antibodies in these patients could lead to immune enhancement and a systemic inflammatory response akin to what is seen with multisystem inflammatory syndrome in children (MIS-C).

Across RNA-based vaccine candidates, observed adverse effects reported to date have been similar to those experienced with the seasonal influenza vaccination, but may be more common given the two-dose schedule for most SARS-CoV-2 mRNA vaccines:

  • Pain at the injection site (up to 60%)
  • Fever (up to 50%)
  • Headache (up to 42%)
  • Fatigue (up to 28%)
  • Joint pain (up to 24%)

Are any trials of SARS-CoV-2 vaccines being done in immunocompromised populations?

There are no published data on SARS-CoV-2 vaccines in immunosuppressed subjects. Most SARS-CoV-2 vaccine studies require patients to be off immunosuppression for a certain period of time to be eligible. This may not be feasible in patients who are receiving therapy for solid organ transplant, graft versus host disease or hematologic malignancy. It is unclear how the different SARS-CoV-2 vaccine candidates will specifically affect different forms of immune abnormalities. Given the diversity of various immunocompromised patient populations, it is possible that candidate SARS-CoV-2 vaccines may differ in their efficacy and safety for these patients.

If immunocompromised patients were not included in the vaccine trials and are less likely to respond to a SARS-CoV-2 vaccine, should they still receive it? What is the timing in relation to chemotherapy, transplant, antibody therapy, splenectomy etc. Should higher vaccine doses or multiple vaccine types be used?

A full discussion of vaccination in patients undergoing stem-cell transplantation or CAR-T therapy is available in a separate FAQ. The risks and benefits for immunocompromised patients receiving a SARS-CoV-2 vaccine should be weighed on a case-by-case basis, with consideration of the incidence of infection in the community. This will depend on the approved vaccine formulation available, level of immunosuppression the patient has received, and the underlying reason for immunosuppressive therapy (e.g., cancer treatment, transplantation). If plans to proceed with the SARS-CoV-2 vaccine are made, vaccination is recommended at least two to four weeks prior to the planned immunosuppressive therapy, transplant or splenectomy. If the patient is receiving or has received immunosuppressive therapy, consider vaccination six months after the patient has been taken off therapy to increase the likelihood of developing immunity (see potential laboratory testing). After hematopoietic cell transplantation, inactivated vaccines have generally shown low incremental risks and have not caused or worsened graft-versus-host disease; thus, inactivated vaccines are generally started after three to six months. If SARS-CoV-2 infection rates are low in a community and a given patient is expected to have improved immune status in upcoming months, clinical judgment is appropriate when weighing the desire for protection as early as possible versus delaying vaccination to give the best chance for response. These recommendations may change, based on the results of the approved vaccine trials. Most experts recommend vaccination as long as the vaccine is safe for use, even if the expected protection rate is lower than the general population.

Importantly, vaccination does not change required precautionary behaviors such as masking, social distancing, and frequent hand hygiene. Influenza vaccination should also be administered to immunocompromised patients to reduce the burden of influenza infection and possible dual infection with SARS-CoV-2. Finally, all healthcare workers and household contacts should receive a SARS-CoV-2 vaccine when available to help protect immunocompromised patients, similar to the recommendations for influenza.

Whether or not an immunocompromised patient is known to have been previously infected with SARS-CoV-2 should not affect the decision of whether to vaccinate. Although some immunity is anticipated from experiencing a COVID-19 clinical infection, this immunity may be insufficient or wane,14,15 especially in immunocompromised hosts. However, increased adverse effects could be seen with vaccination, similar to what is observed with the second dose in a two-dose vaccine series.

Until more is known, different SARS-CoV-2 vaccines should not be given to the same patient. Although measuring titers may eventually be helpful to assess response, more information is needed. Giving more inoculations or higher doses of an approved SARS-CoV-2 vaccine is not recommended at this time.


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