Cystic fibrosis (CF) is a complex genetic disorder that profoundly affects the respiratory and digestive systems. Over the past few decades, advances in treatment—particularly the introduction of CFTR modulator therapies such as ivacaftor-lumacaftor and elexacaftor-tezacaftor-ivacaftor—have significantly extended life expectancy. This shift in longevity has brought long-term complications to the forefront of clinical care. The most common of these complications is cystic fibrosis-related diabetes (CFRD). CFRD develops when progressive pancreatic fibrosis and inflammation disrupt the production and secretion of insulin. Unlike type 1 diabetes, there is no autoimmune destruction of beta cells; unlike type 2 diabetes, insulin resistance is not the primary defect. Instead, CFRD is a distinct disease characterized by both insulin deficiency and intermittent insulin resistance, the latter usually triggered by infection or inflammation.

The intersection of CF and diabetes creates a cascade of health vulnerabilities. Lung function declines more rapidly in patients with CFRD compared to those with CF alone, and the risk of severe pulmonary exacerbations is substantially elevated. Managing blood glucose levels is made more difficult by the high-calorie, high-fat nutritional requirements of CF, the need for frequent antibiotic courses, and the metabolic stress of chronic inflammation. Within this clinical picture, preventive medicine takes on heightened importance. Vaccinations are a foundational strategy for preserving lung function, maintaining metabolic stability, and preventing avoidable hospitalizations in this high-risk population.

Why People with CFRD Are at Greater Risk from Infections

Compromised Immune Defenses

The immune system in CF is chronically activated but functionally impaired. Thick mucus traps bacteria in the airways, creating a persistent nidus for infection. Furthermore, high blood glucose levels directly impair white blood cell function, particularly neutrophil chemotaxis and phagocytosis. Hyperglycemia also impairs the complement system and reduces antibody production in response to new antigens. This means that even a relatively mild viral illness, such as rhinovirus or influenza, can rapidly escalate into a serious secondary bacterial infection, including hospital-acquired pathogens like Pseudomonas aeruginosa or methicillin-resistant Staphylococcus aureus. The result is often a vicious cycle: infection worsens hyperglycemia, which further impairs immune clearance, prolonging the infection and accelerating lung function decline.

The Metabolic Toll of Infection

When a patient with CFRD contracts a respiratory infection, the body mounts a stress response characterized by the release of cortisol and pro-inflammatory cytokines like interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha). These hormones induce profound insulin resistance. In a person with limited pancreatic insulin reserves, this leads to severe hyperglycemia. High blood glucose further impairs immune function and accelerates fluid and electrolyte shifts, increasing the risk of diabetic ketoacidosis (DKA) or hyperosmolar hyperglycemic state (HHS). Hospitalizations for DKA are not uncommon in CFRD patients during pulmonary exacerbations. Vaccination helps break this dangerous cycle by reducing the frequency and severity of infections, thereby preserving metabolic stability.

Evidence-Based Vaccination Schedule for CFRD

Patients with CFRD should follow an intensified vaccination schedule that accounts for their immunocompromised status. The Centers for Disease Control and Prevention (CDC) recommends several key vaccines for adults with diabetes and chronic lung disease, and the Cystic Fibrosis Foundation offers specific guidance for the CF population. Additionally, the Advisory Committee on Immunization Practices (ACIP) provides category A recommendations for many of these vaccines in immunocompromised adults.

Influenza Vaccination

Annual influenza vaccination is the single most important vaccine for patients with CFRD. Influenza triggers severe pulmonary exacerbations and can cause weeks of metabolic instability. The high-dose or adjuvanted quadrivalent flu vaccine is often preferred over the standard dose for patients with CF because it elicits a more robust immune response. Studies have demonstrated that influenza vaccination significantly reduces the rate of hospitalizations for respiratory complications in the CF population. The vaccine should be administered annually, ideally by early fall, to ensure protection throughout the entire flu season. The injectable inactivated vaccine is recommended; the live attenuated intranasal spray is generally not advised for patients with chronic pulmonary conditions or compromised immunity. It is important to note that egg allergy is no longer a contraindication to receiving any licensed influenza vaccine, including those grown in eggs.

Pneumococcal Vaccination

Streptococcus pneumoniae is a common cause of pneumonia and bacteremia in patients with chronic lung disease. The pneumococcal vaccination schedule for adults with CFRD has evolved with the introduction of higher-valency conjugate vaccines. Current CDC and ACIP guidelines recommend a single dose of PCV20 (pneumococcal conjugate vaccine covering 20 serotypes) for adults aged 19 and older who have not previously received a pneumococcal conjugate vaccine. Alternatively, patients may receive PCV15 followed by PPSV23 (pneumococcal polysaccharide vaccine) at least one year later. For those who have already received PPSV23 but not a conjugate vaccine, PCV20 is indicated at least one year after the last PPSV23 dose. In some cases, revaccination with PPSV23 may be considered for those at highest risk, such as patients with advanced lung disease or prior invasive pneumococcal disease. Ensuring up-to-date pneumococcal immunization is essential for preventing invasive pneumococcal disease, which can be catastrophic in a patient with compromised lung function.

COVID-19 Vaccination and Updated Boosters

SARS-CoV-2 infection poses a substantial risk to individuals with CF and CFRD. The combination of underlying lung disease, immune dysfunction, and metabolic instability increases the likelihood of severe illness, hospitalization, and long COVID. Updated mRNA vaccines (targeting Omicron subvariants such as XBB.1.5) provide better protection against currently circulating strains. Patients with CFRD should receive the recommended number of doses of the updated vaccine, typically an annual booster for those who are up to date with their primary series. For moderately or severely immunocompromised individuals, including those with CF who are on immunosuppressive therapies (e.g., post-transplant or for allergic bronchopulmonary aspergillosis), additional doses may be warranted as per CDC guidelines. Vaccination against COVID-19 is safe and remains the most effective tool for preventing severe outcomes.

Respiratory Syncytial Virus (RSV) Vaccination

RSV is a significant cause of acute respiratory illness in adults, particularly those with chronic heart and lung conditions. The approval of RSV vaccines for older adults and for adults with chronic medical conditions represents a major advancement. The CDC now recommends RSV vaccination for adults aged 60 and over, and for adults aged 19–59 with chronic lung disease, including CF. Given the high burden of RSV in the CF population—where it can trigger severe exacerbations and prolonged liver function abnormalities—patients with CFRD should discuss RSV vaccination with their care team. The recombinant RSV vaccine (Arexvy) or the adjuvanted vaccine (Abrysvo) are options depending on age and prior immunization status. Administering RSV vaccine before the fall respiratory virus season is ideal.

Hepatitis B Vaccination

Liver disease is a common extrapulmonary manifestation of CF, ranging from steatosis to cirrhosis with portal hypertension. Hepatitis B infection can accelerate liver damage and complicate the management of CFRD. Hepatitis B vaccine is recommended for all adults with chronic liver disease, including those with CF-related liver disease. A standard 3-dose series (Engerix-B or Recombivax HB) is administered at 0, 1, and 6 months. For patients who may have suboptimal response due to chronic illness or immunosuppression, a high-dose formulation (Heplisav-B, 2 doses) may be considered. Post-vaccination serologic testing (quantitative anti-HBs) is sometimes performed 1–2 months after completion to confirm protective antibody levels (≥10 mIU/mL), particularly in patients at higher risk of non-response. If immunity is inadequate, a second full series is recommended.

Pertussis and Tetanus (Tdap)

Pertussis (whooping cough) is highly contagious and can trigger severe coughing fits that exacerbate lung damage and increase the risk of pneumothorax in CF patients. All adults with CFRD should receive a single dose of Tdap (tetanus, diphtheria, and acellular pertussis) if they have not previously received it. After that, a Td booster every 10 years is sufficient. For women, Tdap is also recommended during each pregnancy to provide passive protection to the newborn—important for CF families. Cocooning (vaccinating close contacts) further reduces the risk of pertussis transmission.

Herpes Zoster (Shingles) Vaccination

The recombinant zoster vaccine (Shingrix) is recommended for immunocompromised adults aged 19 and older who are at increased risk for herpes zoster (shingles). Chronic stress, steroid use, and underlying immune dysfunction may place CF patients at higher risk. Shingrix is given as two doses, 2–6 months apart, and is safe for use in patients with CF. The live zoster vaccine (Zostavax) is contraindicated in immunocompromised individuals and should not be used.

Measles, Mumps, Rubella (MMR) and Varicella

Young adults with CFRD should have documented immunity against measles, mumps, rubella, and varicella. Although these live attenuated vaccines are generally safe in patients with CF (who are not severely immunocompromised unless on high-dose corticosteroids or post-transplant), they should be administered only after careful assessment of immune status. For patients who are not on immunosuppressive therapy, MMR and varicella vaccines can be given. If there is any doubt, serologic testing for IgG antibodies can guide decisions. These vaccines are particularly important given the potential for community outbreaks.

The Role of CFTR Modulators in Vaccine Response

CFTR modulator therapies, such as elexacaftor-tezacaftor-ivacaftor, have dramatically improved lung function, reduced the frequency of pulmonary exacerbations, and improved nutritional status in many CF patients. Some evidence suggests that these therapies may also enhance the immune response to vaccinations. For example, studies have shown improved seroconversion rates to influenza and SARS-CoV-2 vaccines in patients on modulators compared to those not on therapy. This is likely due to reduced systemic inflammation and improved overall health. However, vaccine coverage should not be deferred until after modulator therapy is initiated—vaccinations should be given regardless, as the benefits of protection far outweigh any theoretical delay.

Coordinating Vaccination Across the Care Team

Effective vaccine delivery in CFRD requires careful coordination. The CF care team typically includes a pulmonologist, endocrinologist, dietitian, nurse coordinator, pharmacist, and social worker. Embedding vaccine assessment into routine CF clinic visits improves adherence. Standing orders that allow nurses to administer vaccines during quarterly visits reduce the burden on patients and families. The electronic health record should be configured to track immunization history, provide prompts for due vaccines, and document vaccination in registry systems. Collaboration with community pharmacies and primary care providers can further improve access, especially for seasonal vaccines like influenza and COVID-19. For patients who are hospitalized for pulmonary exacerbations, using that opportunity to catch up on overdue vaccines can significantly reduce missed opportunities.

Safety and Immune Response in CFRD

A common question is whether vaccines are as effective in patients with CF. Research indicates that while the immune response can be blunted in advanced disease or during periods of poor glycemic control, most patients mount protective antibody levels to routine vaccines. The safety profile of vaccines in CF is excellent. Standard adverse events such as local injection site pain, fatigue, and low-grade fever are common but self-limited. There is no evidence that vaccines exacerbate CF lung disease or worsen glycemic control in the short term. Concerns about disease exacerbations are unfounded; the benefit of preventing severe infection vastly outweighs any theoretical risk. Patients with a history of severe allergic reaction to a vaccine component should consult with an allergist or immunologist. However, most patients with CF and CFRD can safely receive all standard vaccines, including those with preservatives or adjuvants.

Overcoming Barriers to Vaccination

Despite strong evidence, vaccination rates in the adult CF population remain suboptimal. Common barriers include a lack of awareness about specific recommendations (such as for RSV or pneumococcal vaccines), concern about side effects, logistical challenges in getting to appointments, needle phobia, and misinformation circulating online. Education is key. Clear, consistent messaging from the entire care team—especially during annual CFRD review visits—about the metabolic and respiratory benefits of vaccination can improve uptake. Offering vaccinations in the CF clinic at the same time as regular lab draws, pulmonary function tests, or CFTR modulator therapy monitoring reduces the number of visits required. Automated reminder systems, including text messages or patient portal notifications, can prompt patients when vaccines are due. For patients who travel to CF centers far from home, arranging vaccination at local pharmacies or primary care offices with shared electronic records can improve compliance.

Vaccination Before Lung Transplantation

Many patients with advanced CF and CFRD will eventually be evaluated for lung transplant. Pre-transplant vaccination is critical because post-transplant immunosuppression markedly impairs vaccine responses and prohibits the use of live vaccines. Ideally, the full vaccination series (including pneumococcal, influenza, COVID-19, RSV, Tdap, hepatitis B, and zoster) should be completed before listing. The transplant team should review immunization records at the time of evaluation and coordinate any catch-up vaccines. Live vaccines (MMR, varicella, yellow fever, live influenza, zoster) must be given at least 4 weeks before transplant or are otherwise contraindicated post-transplant. This process requires forward planning and close communication between the CF center and the transplant program.

The Role of Family and Caregivers

Protecting patients with CFRD also involves vaccinating close contacts. Household members and caregivers should receive annual influenza and COVID-19 vaccines to reduce the risk of introducing infections into the home. They should also have up-to-date Tdap and, if eligible, RSV vaccine. This "cocooning" strategy is especially important because many CF patients acquire infections from family members. The Cystic Fibrosis Foundation provides comprehensive resources for managing CFRD, including disease-specific vaccination guidelines that emphasize family vaccination.

Practical Steps for Protecting Patients with CFRD

Patients and caregivers can take ownership of the vaccination schedule by maintaining an up-to-date immunization record and reviewing it at every annual visit. A simple checklist can help: annual influenza, updated COVID-19, pneumococcal (PCV20 or PCV15 + PPSV23), RSV (if age/risk appropriate), hepatitis B series, Tdap (once then Td every 10 years), zoster (Shingrix series), and documentation of MMR/varicella immunity. Travel vaccines (yellow fever, hepatitis A, typhoid, meningococcal) should be discussed at least 4–6 weeks before planned international travel.

Prioritizing vaccination is one of the most effective actions a person with CFRD can take to protect their lung function and maintain metabolic stability. By reducing the burden of acute respiratory infections, vaccines allow patients to focus on the daily demands of CF care—airway clearance, enzyme replacement, insulin management, and nutritional support—and enjoy a higher quality of life. The integration of preventive immunizations into the standard CFRD care plan is not just an option; it is a standard of care that can reduce hospitalizations, slow lung function decline, and improve outcomes.