3.2 Immunizations for Special Populations: Pregnancy, Asplenia, Immunocompromised, and Chronic Conditions

3.2 Immunizations for Special Populations: Pregnancy, Asplenia, Immunocompromised, and Chronic Conditions

Core Clinical Principle: High-risk patient populations exhibit altered immunological responses, heightened vulnerability to invasive encapsulated infections, or potential physiological risks to fetal development. Pharmacy technicians must strictly identify which vaccines are mandatory, which are contraindicated, and the exact timing thresholds that govern safe administration in maternal health, asplenia, immunosuppression, and chronic disease states.

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1. Maternal Immunization: Pregnancy and Lactation

Maternal vaccination serves a dual purpose: protecting the pregnant individual against severe illness and mortality while facilitating active transplacental IgG transfer to protect the infant during the vulnerable first six months of life before pediatric vaccine series achieve protective titers.

+---------------------------------------------------------------------------------------------------+
|                              MATERNAL IMMUNIZATION PROTOCOLS (PREGNANCY)                          |
|                                                                                                   |
|   VACCINE              GESTATIONAL TIMING              CLINICAL RATIONALE                         |
|   ------------------   -----------------------------   ----------------------------------------   |
|   Inactivated Flu      Any Trimester (Seasonally)      Prevents severe maternal cardiopulmonary   |
|   (IIV / RIV)                                          complications and newborn influenza.       |
|                                                                                                   |
|   Tdap                 27 through 36 Weeks Gestation   Optimizes transplacental transfer of       |
|                        (EVERY single pregnancy)        maternal anti-pertussis IgG antibodies.    |
|                                                                                                   |
|   RSV (Abrysvo ONLY)   32 through 36 Weeks Gestation   Protects infant against severe lower       |
|                        (Sept–Jan in contiguous US)     respiratory tract disease (LRTD).          |
|                                                                                                   |
|   COVID-19             Any Trimester                   Prevents severe maternal ICU admission,    |
|   (Updated mRNA)                                       stillbirth, and preterm delivery.          |
+---------------------------------------------------------------------------------------------------+

Tdap in Pregnancy: The 27–36 Week Window

• Recommended During Every Pregnancy: ACIP recommends administering one dose of Tdap during EACH pregnancy, regardless of the patient's prior history of receiving Td or Tdap.
• Optimal Timing: Administered between 27 and 36 weeks gestation (preferably early in this window, around weeks 27–30). This allows 2 to 4 weeks for maternal B-cell antibody production and active neonatal Fc receptor-mediated transplacental IgG transport, resulting in high cord-blood pertussis antibody titers.
• Postpartum Catch-Up: If a patient has never received Tdap and it was not administered during pregnancy, CDC recommends postpartum Tdap; a patient who previously received Tdap does not need an additional postpartum dose solely because the pregnancy window was missed.

Maternal RSV Vaccination (Abrysvo)

• Approved Formulation: Only Pfizer's Abrysvo (unadjuvanted bivalent RSVpreF) is approved and recommended by ACIP for pregnant individuals. GSK's Arexvy and Moderna's mResvia are NOT approved in pregnancy.
• Timing: Administer one dose at 32 0/7 through 36 6/7 weeks gestation from September through January across most of the continental United States. CDC does not currently recommend another maternal RSV vaccine dose in a subsequent pregnancy; the infant should receive recommended monoclonal antibody protection instead.
• Alternative Strategy: If maternal Abrysvo is given >=14 days before delivery, the newborn generally does not need infant RSV antibody. If the mother is unvaccinated, maternal status is unknown, or delivery occurs <14 days after vaccination, an eligible infant younger than 8 months receives nirsevimab (Beyfortus) or clesrovimab (Enflonsia); only nirsevimab is recommended for eligible high-risk children entering a second RSV season.

Contraindicated Vaccines During Pregnancy

• Live Vaccines: MMR, Varicella, Live Attenuated Influenza (LAIV), and Live Oral Typhoid (Ty21a) are contraindicated during pregnancy. Yellow fever is a precaution, not an absolute contraindication: if travel is unavoidable and exposure risk outweighs vaccination risk, it may be given after clinical assessment; otherwise defer travel or issue a waiver.
• Conception Deferral: Women receiving live vaccines must be advised to avoid pregnancy for at least 28 days (4 weeks) after vaccination.
• Accidental Administration: If a live vaccine is inadvertently given during pregnancy, the patient should be reassured that adverse fetal outcomes have not been documented, and pregnancy termination is NOT recommended.
• Lactation Safety: Breastfeeding is not a contraindication to most vaccines, including MMR and varicella. Yellow fever vaccination is generally avoided while breastfeeding because rare infant meningoencephalitis has occurred; if travel cannot be avoided, the clinician weighs exposure risk and follows current CDC guidance.

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2. Anatomic and Functional Asplenia

Patients with anatomic asplenia (surgical splenectomy, congenital asplenia) or functional asplenia (Sickle Cell Disease, hemoglobinopathies, severe celiac disease) lack splenic macrophage phagocytosis and IgM-secreting marginal zone B-cells. They face life-threatening susceptibility to encapsulated bacterial pathogens, leading to Overwhelming Post-Splenectomy Infection (OPSI) with rapid-onset septic shock and a mortality rate exceeding 50%.

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|                           VACCINE PROTOCOLS FOR ASPLENIA / SICKLE CELL DISEASE                    |
|                                                                                                   |
|   TARGET PATHOGEN               RECOMMENDED VACCINE REGIMEN & SCHEDULE                            |
|   ----------------------------  ---------------------------------------------------------------   |
|   Streptococcus pneumoniae      - PCV20 (Single Dose), OR                                         |
|   (Pneumococcal)                - PCV15 (1 Dose) followed by PPSV23 >=8 Weeks Later.              |
|                                                                                                   |
|   Neisseria meningitidis        - MenACWY (MenQuadfi / Menveo): 2-Dose Primary Series             |
|   (Meningococcal Serogroups     (spaced >=8 weeks apart) + Booster Every 5 Years for life.        |
|    A, C, W, Y and B)            - MenB (Bexsero or Trumenba 3-dose series at         |
|                                 0, 1-2, 6 mo) + Booster at 1 Year and Every 2-3 Years.            |
|                                                                                                   |
|   Haemophilus influenzae type b - Hib (ActHIB / Hiberix / PedvaxHIB): 1 Dose in adulthood        |
|   (Hib)                         if not previously vaccinated during childhood.                    |
+---------------------------------------------------------------------------------------------------+

Timing for Elective vs. Emergency Splenectomy

• Elective Splenectomy (Planned Surgery): Administer all indicated vaccines (Pneumococcal, MenACWY, MenB, Hib) at least 14 days prior to surgery to maximize splenic antigen capture and antibody titer generation.
• Emergency Splenectomy (Trauma): Defer vaccination until post-operative day 14 (or at hospital discharge) because immediate post-surgical immunologic paralysis blunts antibody seroconversion.

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3. Altered Immunocompetence (Immunosuppression)

Immunocompromise arises from congenital immunodeficiencies, HIV infection, malignant neoplasms, solid organ or hematopoietic stem cell transplants, and immunosuppressive pharmacotherapy.

Defining Severe Immunosuppression Thresholds

1. High-Dose Systemic Corticosteroids: Defined by ACIP as receiving >=20 mg/day of prednisone (or >=2 mg/kg/day for children) for 14 or more consecutive days. Live vaccines are contraindicated during therapy and for at least 1 month (28 days) after cessation.
   • Non-Immunosuppressive Steroid Regimens: <20 mg/day prednisone, short courses (<14 days), alternate-day physiologic replacement, topical, inhaled, or intra-articular injections do NOT contraindicate live vaccines.
2. HIV Infection:
   • CD4 < 200 cells/mm3 (or CD4% < 15%): Severe immunosuppression. ALL live vaccines (MMR, Varicella, LAIV) are strictly CONTRAINDICATED.
   • CD4 >= 200 cells/mm3 (and CD4% >= 15%) for >=6 months: MMR (2 doses >=28 days apart) and Varicella (2 doses >=3 months apart) may be administered if non-immune.
3. Biologic DMARDs and Targeted Immunosuppressants: TNF-alpha inhibitors (infliximab, adalimumab, etanercept), anti-CD20 monoclonal antibodies (rituximab), IL-6 inhibitors, and JAK inhibitors contraindicate live vaccines. Inactivated vaccines should be given at least 2 weeks prior to initiating biologics.

Recombinant Zoster Vaccine (Shingrix) in Immunocompromised Adults

• Indications: Shingrix is a non-live, recombinant glycoprotein E adjuvanted vaccine indicated for all immunocompromised adults aged 19 years and older (including patients with HIV, solid organ transplant, hematologic malignancy, and autoimmune diseases on immunosuppression).
• Dosing Schedule: 2-dose series (0 and 2–6 months; can use an accelerated 0 and 1–2 month schedule if immunosuppression is imminent).

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4. Chronic Medical Conditions