9.3 Adult Immunization Schedules & ACIP Recommendations

Adult Immunization Schedules & ACIP Recommendations

Executive Summary: Vaccines represent one of the highest-impact, most cost-effective clinical preventive services in ambulatory care. The Advisory Committee on Immunization Practices (ACIP) of the CDC publishes annual, evidence-based recommendations outlining routine adult vaccination schedules by age and medical condition. Ambulatory care pharmacists must master recent major schedule updates, including conjugate pneumococcal vaccination algorithms (PCV20 vs. PCV15 + PPSV23), high-dose influenza preferential recommendations for older adults, the recombinant zoster (Shingrix) 2-dose series, maternal and older adult RSV indications, and clinical shared decision-making for HPV in adults aged 27–45.

1. Influenza Vaccination: Universal & Enhanced Formulations

Universal Recommendation

• Target Population: Annual influenza vaccination is recommended for all persons aged ≥ 6 months who do not have contraindications, ideally administered in September or October prior to widespread community influenza circulation.

Enhanced Formulations for Adults Aged ≥ 65 Years

Due to immunosenescence (age-related decline in innate and adaptive immune responsiveness), older adults mount lower antibody titers and experience higher rates of influenza-related hospitalization and death. ACIP preferentially recommends three enhanced influenza vaccine formulations for all adults aged ≥ 65 years:

1. High-Dose Inactivated Influenza Vaccine Quadrivalent (HD-IIV4, Fluzone High-Dose): Contains 4 times the antigen content (60 mcg of hemagglutinin per strain vs. 15 mcg in standard-dose vaccines; total 240 mcg), demonstrating superior relative efficacy in preventing laboratory-confirmed influenza.
2. Recombinant Influenza Vaccine Quadrivalent (RIV4, Flublok): Contains 3 times the antigen content (45 mcg of hemagglutinin per strain; total 180 mcg) produced via insect cell baculovirus expression technology, completely egg-free.
3. Adjuvanted Inactivated Influenza Vaccine Quadrivalent (aIIV4, Fluad): Formulated with the MF59 oil-in-water squalene adjuvant to amplify and broaden the immune response.

• Clinical Rule: If none of these three preferentially recommended enhanced vaccines is available at the time of the clinic encounter, an age-appropriate standard-dose unadjuvanted inactivated influenza vaccine should be administered without delay.

Egg Allergy Guidelines (Updated ACIP Consensus)

Persons with a history of egg allergy of any severity (including hives, angioedema, respiratory distress, lightheadedness, or anaphylaxis requiring epinephrine) may receive any licensed, recommended, and age-appropriate influenza vaccine (inactivated, recombinant, or live attenuated). Special settings, allergy consultation, or extended 30-minute observation periods are no longer required.

2. Pneumococcal Immunization Algorithms (PCV15, PCV20, PPSV23)

ACIP recommendations for pneumococcal vaccination protect against invasive pneumococcal disease (bacteremia, meningitis) and pneumococcal pneumonia caused by Streptococcus pneumoniae.

Qualifying Indications for Pneumococcal Vaccination

1. All Adults Aged ≥ 65 Years (universal age-based recommendation).
2. Adults Aged 19–64 Years with Underlying Chronic Conditions:
   • Chronic Medical Conditions: Diabetes mellitus, chronic heart disease (heart failure, cardiomyopathies; excluding hypertension alone), chronic lung disease (COPD, asthma, emphysema), chronic liver disease (cirrhosis, hepatitis), cigarette smoking, alcoholism.
   • Immunocompromising Conditions & High-Risk Anatomical Defects: Chronic kidney disease (CKD Stages 3–5, ESRD/dialysis), nephrotic syndrome, anatomic or functional asplenia (sickle cell disease), congenital or acquired immunodeficiencies, HIV infection, generalized malignancy, hematologic cancers (leukemia, lymphoma, multiple myeloma), solid organ transplant, immunosuppressive medications (high-dose systemic steroids, biologics, chemotherapy), cochlear implants, and cerebrospinal fluid (CSF) leaks.

Pneumococcal Vaccine Regimen Options for Naive Adults

For pneumococcal vaccine-naive patients (those who have never received any pneumococcal conjugate or polysaccharide vaccine):

┌────────────────────────────────────────────────────────────────────────┐
│            PNEUMOCOCCAL VACCINATION IN NAIVE ADULTS (≥65 or 19-64 RISK) │
├──────────────────────────────────┬─────────────────────────────────────┤
│ OPTION 1: PCV20 (Prevnar 20)     │ OPTION 2: PCV15 (Vaxneuvance)       │
│ • Administer 1 DOSE PCV20 ALONE  │ • Administer 1 DOSE PCV15           │
│ • SERIES COMPLETE!               │   FOLLOWED BY                       │
│ • No subsequent PPSV23 required  │ • 1 DOSE PPSV23 (Pneumovax 23)      │
│                                  │   - Interval: ≥ 1 YEAR later        │
│                                  │     (Shortened to ≥ 8 WEEKS for     │
│                                  │     immunocompromised, CSF leak,    │
│                                  │     or cochlear implants)           │
└──────────────────────────────────┴─────────────────────────────────────┘

Navigation of Prior Pneumococcal Vaccination History

• If Patient Previously Received PPSV23 Only: Administer 1 dose of PCV20 or PCV15 at least 1 year after the last PPSV23 dose. (If PCV15 is selected, no further PPSV23 is required).
• If Patient Previously Received PCV13 Only: Administer 1 dose of PCV20 at least 1 year after PCV13 OR complete the previously recommended PPSV23 series as scheduled.
• If Patient Received PCV13 + PPSV23 Prior to Age 65: At age ≥ 65, administer 1 dose of PCV20 (at least 5 years after the last pneumococcal vaccine dose) to provide broader serotype coverage.

3. Respiratory Syncytial Virus (RSV) & COVID-19 Vaccines

Respiratory Syncytial Virus (RSV) in Older Adults

RSV causes significant lower respiratory tract disease, hospitalization, and mortality in older adults, particularly those with cardiopulmonary comorbidities.

Current ACIP RSV Recommendations (Single Lifetime Dose)

1. Routine Universal Recommendation: Administer a single dose of any approved RSV vaccine to all adults aged ≥ 75 years.
2. Risk-Stratified Recommendation: Administer a single dose to adults aged 60–74 years who are at increased risk of severe RSV disease, including:
   • Chronic cardiovascular disease (heart failure, CAD, cardiomyopathy).
   • Chronic pulmonary disease (COPD, moderate-to-severe asthma, interstitial lung disease).
   • Endocrine disorders (Diabetes mellitus with end-organ damage or requiring insulin).
   • Chronic kidney disease (Stages 3–5) or chronic liver disease.
   • Severe obesity ($BMI \ge 40 \text{ kg/m}^2$).
   • Residents of nursing homes and long-term care facilities.
   • Moderate-to-severe immunocompromise.

• Timing & Administration: RSV vaccine is administered as a single lifetime dose (annual revaccination is not currently recommended) and can be co-administered with annual influenza and COVID-19 vaccines.

COVID-19 Vaccination (Updated Seasonal Formulations)

• Universal Schedule: ACIP recommends 1 updated seasonal dose (mRNA vaccines: Pfizer-BioNTech Comirnaty or Moderna Spikevax; or protein subunit: Novavax) for all individuals aged ≥ 6 months, administered at least 2 months after any previous COVID-19 vaccine dose.
• Older Adults (Aged ≥ 65 Years) & Immunocompromised: Recommended to receive 1 additional dose of the updated COVID-19 vaccine at least 4 months (for older adults) or at least 2 months (for immunocompromised) following the initial updated seasonal dose.

4. Recombinant Zoster (Shingrix), Tdap/Td & HPV Vaccines

Herpes Zoster: Recombinant Zoster Vaccine (RZV, Shingrix)

Herpes zoster (shingles) results from reactivation of latent varicella-zoster virus (VZV) in dorsal root or cranial nerve ganglia, often complicated by debilitating postherpetic neuralgia (PHN).

• Vaccine Composition: Shingrix is a non-live, recombinant subunit vaccine containing glycoprotein E combined with the potent AS01B adjuvant system.
• Efficacy: Exceeds 90% efficacy in preventing herpes zoster and PHN across all age groups, with sustained immunity lasting over a decade.
• Schedule & Dosing: 2-dose series administered intramuscularly (0.5 mL IM) at Months 0 and 2–6.
  • Accelerated Interval: For immunocompromised patients who would benefit from completing the series rapidly, the interval between doses may be shortened to 1 to 2 months.
• Target Populations:
  1. All immunocompetent adults aged ≥ 50 years.
  2. Immunocompromised adults aged ≥ 19 years who are or will be at increased risk of zoster.
• Key Clinical Rules:
  • Administer Shingrix regardless of whether the patient reports a prior history of chickenpox or shingles.
  • Administer Shingrix even if the patient previously received the discontinued live zoster vaccine (Zostavax); give Shingrix at least 2 months after Zostavax.
  • Do NOT administer Shingrix during an active, acute shingles outbreak; wait until acute symptoms resolve.

Tetanus, Diphtheria, Pertussis (Tdap / Td)

• Primary Adult Booster: Adults who have never received a dose of Tdap should receive 1 dose of Tdap immediately, followed by a booster dose of Td or Tdap every 10 years throughout life.
• Pregnancy Indication: Administer 1 dose of Tdap during EACH pregnancy, regardless of prior vaccination history, optimally between 27 and 36 weeks of gestation (maximizes transplacental maternal anti-pertussis IgG transfer to protect the newborn prior to their childhood DTaP series).
• Wound Prophylaxis Management:
  • Clean, Minor Wounds: Administer Td or Tdap only if ≥ 10 years have elapsed since the last tetanus-containing toxoid dose.
  • Contaminated / Dirty / Puncture / Animal Bite Wounds: Administer Td or Tdap if ≥ 5 years have elapsed since the last dose. If the patient has received < 3 prior doses or vaccination history is unknown, administer both Tdap AND Tetanus Immune Globulin (TIG 250 units IM) at separate anatomical sites.

Human Papillomavirus (HPV: 9-Valent, Gardasil 9)

Protects against high-risk oncogenic HPV types (16, 18, 31, 33, 45, 52, 58) causing cervical, anogenital, and oropharyngeal cancers, and low-risk types (6, 11) causing anogenital warts.

• Routine Vaccination: Recommended for all individuals through age 26 who were not adequately vaccinated previously.
  • 2-Dose Series (0, 6–12 months): If the primary series was initiated before the 15th birthday.
  • 3-Dose Series (0, 1–2, 6 months): If initiated at age ≥ 15 years, or for immunocompromised individuals of any age.
• Clinical Shared Decision-Making (Aged 27–45 Years): For adults aged 27 through 45 years who are not adequately vaccinated, ACIP recommends clinical shared decision-making. Pharmacists and clinicians should assess the patient's individual risk of new HPV acquisition (e.g., new sexual partners, future relationship changes), noting that HPV vaccine efficacy is highest when administered prior to exposure, though it does not treat existing infections.