Shots and Shields: Why Vaccines Matter Even More During Cancer Treatment

For patients undergoing cancer treatment, infection is one of the leading causes of non-cancer morbidity and mortality within the first year following diagnosis.¹ Patients receiving cytotoxic chemotherapy, anti-CD20 therapy, CAR-T therapy, or hematopoietic stem cell transplant (HSCT) are at particularly elevated risk of acquiring infections with vaccine preventable diseases due to attenuated serologic response during or after therapy or a loss of previously established vaccine immunity.^1,2,3 Although serologic response may be diminished in these populations, vaccination remains one of the most effective public health interventions for preventing severe infection, hospitalization, and death.¹ Revaccination of childhood-recommended vaccine series may be indicated in these patient populations to help supplement the decrease in effectiveness due to antineoplastic therapy.^1,2

According to CDC estimates, influenza vaccination alone prevented nearly 10 million illnesses, 120,000 hospitalizations, and nearly 8,000 deaths during the 2023–24 season. Almost 300 children died from influenza last flu season, the vast majority of whom were unvaccinated.⁴ These deaths underscore the ongoing lethality of influenza in the overall population. For immunocompromised patients, this risk is substantially increased. Observational data suggest influenza vaccination reduces hospitalization risk by approximately 30–50% in patients with solid tumors and reduces severe complications even when antibody titers are lower than what is represented in immunocompetent populations.¹ In practice, vaccination should not be delayed while waiting for optimal blood counts unless clearly contraindicated, as partial protection remains clinically meaningful.

Hospitalization for pneumonia is among the most common infectious complications of cancer treatment.¹ Pneumococcal conjugate vaccines reduce the risk of invasive disease and serious respiratory complications, including pneumonia-related hospitalization.^1,4 In hematologic malignancy populations, conjugate vaccination demonstrates improved immunogenicity compared with polysaccharide-only regimens, though response rates may range from 40–70% depending on therapy timing.^1,2 Pharmacists should verify appropriate sequencing (PCV followed by PPSV when indicated) and align timing with periods of maximal immune recovery when feasible.

In patients with cancer, COVID-19 vaccination has been associated with reduced hospitalization and mortality despite lower seroconversion rates in patients receiving anti-CD20 therapy.¹ Even when seroconversion rates are reduced (20–40% in B-cell–depleted patients), T-cell–mediated immunity likely contributes to observed reductions in severe disease.^1,3 Counseling should emphasize that lower antibody levels do not equate to lack of protection.

Patients with solid tumors and hematologic malignancies demonstrate increased susceptibility to influenza, pneumococcal disease, and other vaccine-preventable infections.^1,4 Although humoral responses may be attenuated in specific subgroups, clinical data indicate that vaccination reduces infection severity, hospitalization, and mortality.^1,3 Oncology pharmacists play a pivotal role in assessing vaccination status throughout active treatment and into survivorship.

HSCT recipients lose preexisting immunity and require revaccination with childhood vaccine series.² Live attenuated vaccines are generally deferred for at least 24 months post-transplant and considered only in the setting of adequate immune reconstitution and absence of ongoing immunosuppression.^1,2,3 Incorporating standardized revaccination checklists into follow-up visits can reduce missed or incomplete series.

CAR-T therapy and anti-CD20 agents may result in prolonged B-cell aplasia and impaired humoral responses. Nonlive vaccines remain safe but may yield reduced immunogenicity. Vaccination timing relative to therapy influences response rates.¹

Advanced age independently increases influenza and pneumococcal mortality risk.⁴ Age-related risk should be considered in addition to treatment-related risk when implementing vaccination strategies.^1,4,6

Vaccination Guidance: Where and What to Look for

The CDC and ACIP remain the gold standard for finding medically appropriate recommendations for vaccinations.⁴ These websites provide guidance on recommended schedules for immunocompetent adults and pediatric populations, as well as special populations including travel, pregnancy, healthcare workers, immigrants, refugees and international adoptions. Additionally, they offer condition-specific guidance for patients with asplenia, diabetes, cardiovascular disease, HIV infection, liver disease, lung disease, kidney disease and weakened immune systems.⁴

In oncology populations, more specific guidance is often needed. Many guidelines have published oncology-specific guidelines to aid clinical decision making regarding continued vaccination or revaccination in patients receiving various cancer therapies.^1,2

Additionally, the AMA has collaborated to create the Vaccine Integrity Project, which is an evidence-based review process to assess vaccine safety and effectiveness to help guide clinical decision making.⁷

Oncology pharmacists are uniquely positioned to develop and maintain treatment-specific vaccination reference guides within their practices that tailor guideline recommendations to align with their workflows and specific patient populations.

Gaps in Coverage

Despite strong scientific consensus supporting vaccination in these populations, recent policy changes and Medicare reimbursement restructuring have introduced new barriers to vaccine access.^1,5

Most ACIP-recommended adult vaccinations are reimbursed under Medicare Part D, which oncology clinics typically cannot directly bill. As a result, vaccines often must be administered in retail pharmacy settings rather than within oncology practices, creating additional coordination challenges and potential barriers to timely immunization. Medicare Part B continues to cover influenza, pneumococcal, hepatitis B (in intermediate or high-risk patient populations clearly defined), COVID-19 vaccines, and other reasonable and necessary vaccines to treat an injury or exposure to a disease. However, specialty clinic vaccination needs become complicated when only some, but not all, vaccines can be administered in the clinic.⁵

This is especially pronounced in the post-transplant/cellular therapy population in which revaccination with complete childhood vaccine series is recommended to re-attenuate serological immunity to preventable infectious diseases.^1,2 Receiving some or all of the required vaccines at the retail pharmacy may result in care fragmentation, documentation gaps, and increasing patient coordination.^5,7 Retail pharmacists may also need education to understand the need for certain vaccinations in adult oncology patients depending on their treatment history.⁸

Furthermore, the American Pharmacists Association Public Vaccine Access Map demonstrates state-level differences in pharmacist prescriptive authority and collaborative practice requirements. Although most states permit pharmacist vaccine administration, variability in scope and billing may influence timeliness of vaccination which directly impacts oncology populations who require time-sensitive vaccination.⁹ As vaccine administration increasingly shifts to the retail pharmacy setting, oncology practices must adopt proactive coordination strategies to maintain preventive care standards.^1,5 Oncology pharmacists are again uniquely positioned to help overcome these barriers through proactive scheduling, cross-setting coordination, documentation reconciliation, and partnership with retail pharmacies.

Overcoming Certain Challenges

One challenge encountered by retail pharmacists because of the CMS updated vaccine coverage guidance is the denial of coverage when billing Part D. If this occurs, retail pharmacists should attempt to bill Part B for coverage.⁵

Another challenge when these vaccines are administered in the retail setting is the stock of available vaccines. Most of these vaccinations are not normally stocked by retail pharmacies because they are not routinely given to typical retail pharmacy patient populations. These vaccinations are often stocked in quantities of 10 vials and are expensive, so if a retail pharmacy is not expected to utilize this stock, there is a potential to lose revenue.⁸ A potential solution is for clinic pharmacists to partner with local retail pharmacies and refer patients to specific pharmacies to ensure vaccine availability and appropriate stock utilization.^7,8 This partnership also establishes a direct route of communication if a prior authorization is necessary for these vaccine prescriptions due to the coverage shift.^5,7

Adequate education to retail pharmacists and patients is paramount when the need for atypical vaccination schedules arise due to treatment.^1,2,8 Many institutions have unique vaccination timelines based on a compilation of the data, so it is important to provide patients and retail pharmacies accurate vaccine schedules and timelines to ensure a smooth transition of care.^1,2

Implementation challenges in 2026 are shaped not only by clinical complexity but also by reimbursement architecture and state-level regulatory variability.^5,9 CMS billing, differences in pharmacy practices, and navigation barriers influence vaccine delivery pathways.⁵

Vaccination in oncology and transplant populations remains supported by robust clinical evidence. The evolving reimbursement landscape amplifies the need for coordinated, pharmacist-led implementation strategies. Preserving preventive standards of care will require deliberate collaboration across oncology clinics, retail pharmacies, and health systems to ensure that immunocompromised patients receive timely and complete protection against preventable infectious diseases.