Current Strategies in Adult Vaccination: Preventing Infections in a Changing Environment

Educational Objectives

The goal of this program is to optimize adult immunization in clinical practice. After hearing and assimilating this program, the clinician will be better able to:

1. Improve administration of COVID-19 vaccines according to current guidelines.
2. Recognize indications for respiratory syncytial virus vaccination in adults.
3. Select appropriate pneumococcal vaccine formulations for different patient populations.

Summary

Current vaccine guideline landscape: the Advisory Committee on Immunization Practices (ACIP) was disbanded in spring 2025 and reconstituted with new members; ACIP has held two meetings with a third deferred, creating uncertainty about future recommendations; the adult immunization schedule has been updated to reflect changes in COVID-19 vaccine recommendations emphasizing shared decision-making; alternative guideline sources have emerged, including the West Coast Health Alliance (California, Hawaii, Oregon, Washington) and the Northeast Public Health Collaborative; individual states and professional organizations are also issuing vaccine recommendations

COVID-19 vaccine recommendations: on September 19, 2024, ACIP changed recommendations to require individual decision-making for all COVID-19 vaccination rather than universal recommendation; this allows coverage through all payment mechanisms; the approach is interpreted as requiring discussion with health care providers about risks and benefits; clinical information from the Centers for Disease Control and Prevention (CDC) remains unchanged from 2024/2025 guidance; US Food and Drug Administration (FDA) approval differs from CDC recommendations, with FDA approval limited to adults ≥65 yr or those with risk factors for severe disease

Regional and professional guidance for COVID-19 vaccines: the West Coast Health Alliance recommends vaccines for all who want them, with particular emphasis on children <2 yr, those never vaccinated, close contacts of high-risk individuals, pregnant or postpartum persons, vulnerable adults, and health care workers; vaccines provide protection against severe disease, hospitalization, and death; protection against infection is time-limited, typically lasting a few months; vaccination decreases risk for long COVID; for those recently infected with COVID-19, deferring vaccination ≈3 mo may be more effective, though earlier administration is safe

Available COVID-19 vaccines: Pfizer mRNA vaccine; Moderna Spikevax (original mRNA vaccine) and new MNEX spike (lower-dose mRNA encoding specific spike protein portion); Novavax protein subunit vaccine (more traditional vaccine technology); all options are available for adults; mild to moderate local and systemic reactions are common with all formulations, possibly slightly less common with Novavax

COVID-19 vaccine efficacy data: data from February 2024 across multiple CDC networks showed ≈33% protection against emergency department (ED) and urgent care visits; protection against hospitalization was higher in adults ≥65 yr; New England Journal study in VA (US veterans) population demonstrated vaccine efficacy of ≈30% for ED visits, 40% for hospitalization, and >60% for COVID-associated death; efficacy levels are comparable to influenza vaccine protection

Myocarditis and pericarditis risk with COVID-19 vaccines: observed most frequently in males aged 12 to 24 yr; highest incidence occurred 7 days after second dose of initial vaccine series, partly attributed to short interval between doses; current vaccination schedules use single-dose regimens for adults (except younger children and immunocompromised patients), eliminating close-interval dosing; almost all patients with vaccine-associated myocarditis fully recovered; risk for myocarditis from COVID-19 infection is substantially higher than risk from vaccination

Respiratory syncytial virus (RSV) vaccines for adults: recommendations—universal vaccination for all adults ≥75 yr; adults aged 50 to 64 yr (previously 60 yr) with increased risk factors for severe RSV; risk factors include nearly any chronic health condition, with nursing home residents at particularly high risk regardless of age; patient self-attestation of risk factors is sufficient for vaccination access at pharmacies without prescription; available vaccines—Aresvo and Abrysvo (stabilized prefusion F protein vaccines) and mRESVIA (Moderna mRNA vaccine encoding same target); efficacy—GSK and Pfizer vaccines demonstrated high efficacy during first season with some decline in second season; current recommendation is single lifetime dose without seasonal revaccination, though ongoing studies are evaluating boosting strategies; post-licensure data confirm trial findings; early signals of Guillain-Barré syndrome with protein vaccines have not shown statistically significant increased risk, though monitoring continues

RSV vaccine efficacy data: mRESVIA showed effectiveness in first year with decline over time but no safety concerns; a randomized controlled trial published August 30, 2024, in New England Journal examined adults ≥60 yr in Denmark with primary endpoint of RSV-associated hospitalization; demonstrated 83% relative vaccine efficacy in first season

RSV prevention in infants: Abrysvo is approved for use during pregnancy at 32 to 36 wk gestation to protect infants; RSV is the most common cause of infant hospitalization; pregnancy vaccination is recommended seasonally (September through January in most US regions); alternative strategy uses long-acting monoclonal antibodies (nirsevimab or clesirovimab) administered directly to infants; both strategies should not be used together; Abrysvo demonstrated 77% efficacy against severe medically attended RSV-associated lower respiratory tract infections in infants; nirsevimab showed ≈75% efficacy for medically attended RSV; clesirovimab demonstrated ≈60% efficacy for medically attended RSV and 84% for hospitalization

Influenza vaccines: universal recommendation—indicated for all individuals ≥6 mo unless contraindicated; contraindications include severe previous reaction to vaccine type and relative contraindication for history of Guillain-Barré syndrome; since 2023, no special considerations are needed for egg allergy regardless of vaccine preparation method; 2025/2026 formulation—change in H3N2 component compared with previous year; H1N1 and B components unchanged; all vaccines are trivalent (one influenza B lineage, Yamagata, disappeared during pandemic and has not been seen since 2021)

Influenza vaccines for older adults: recommended formulations for adults ≥65 yr include higher antigen dose or adjuvanted vaccines, ie, Fluzone High-Dose (4 times standard hemagglutinin dose), adjuvanted Fluad, or recombinant Flublok (3 times standard antigen); the same vaccines are recommended for solid organ transplant patients; high-dose vaccine demonstrates slightly better efficacy than standard dose in most pooled data; recent randomized controlled trials from Denmark and Spain showed small but significant improvements in hospitalization rates with high-dose formulation; recombinant Flublok (approved for ages ≥9 yr) shows slightly higher vaccine efficacy than standard dose and sustained protection

Influenza vaccine policy change: ACIP recommended discontinuing thimerosal-containing influenza vaccines; thimerosal is a mercury-containing preservative used in multidose vials for decades with no known health effects; recommendation had limited impact as most vaccines already single-dose formulations without preservative

Influenza season and vaccine efficacy: 2023-2024 season was most severe in more than a decade with high hospitalization rates; Southern Hemisphere data for 2024-2025 showed ≈50% vaccine effectiveness against both outpatient visits and hospitalizations, suggesting good strain match; Japan had experienced large outbreak in 2024

Influenza vaccination in pregnancy: multiple studies demonstrate safety and effectiveness for pregnant individuals and protection of infants during early life; increased risk for severe disease exists during pregnancy, especially in third trimester; vaccination during pregnancy protects infants during early life when they are most vulnerable

Influenza vaccination timing: vaccination is typically avoided in July and August despite vaccine availability; optimal timing is September and October to balance adequate immunity before peak season while accounting for waning efficacy; vaccination should continue throughout the season as influenza activity can extend late into spring

Pneumococcal vaccines: available formulations: 3 protein conjugate vaccines are currently available (PCV20 [Prevnar 20, 20-valent], PCV15 [Vaxneuvance, 15-valent], and PCV21 [Capvaxive, 21-valent]); polysaccharide vaccine (Pneumovax) previously used in combination strategies; simplified dosing—single dose of PCV20 or PCV21 completes pneumococcal vaccination series for adults at any age; the only exception is revaccination after bone marrow or stem cell transplant; this represents major simplification from previous multidose strategies

Pneumococcal vaccine recommendations: universal vaccination now begins at age 50 yr (previously 65 yr); rationale for age reduction is that invasive pneumococcal disease rates are now similar in 50 to 64 yr age group compared with ≥65 yr age group due to pediatric vaccination program success; adults aged 19 to 49 yr with immunocompromising conditions, cerebrospinal fluid leak, or cochlear implant should receive vaccination; adults aged 19 to 49 yr with chronic medical conditions also indicated for vaccination (frequently overlooked group)

PCV20 vs PCV21 selection: PCV21 contains 8 different serotypes not found in PCV20 despite similar total serotype numbers; PCV21 provides more updated coverage for serotypes circulating in adults; PCV20 includes serotype 4, which may be problematic in certain western states; Alaska Public Health specifically prefers PCV20 over PCV21 due to serotype 4 prevalence; for most patients in other regions, PCV21 may offer slightly more benefit; CDC app and website are available to determine which vaccine is due based on patient vaccination history

Zoster (shingles) vaccine: Shingrix is adjuvanted recombinant vaccine given as 2-dose series; recommended for all adults ≥50 yr and adults aged 19 to 49 yr with immunocompromising conditions; highly effective with 97% efficacy in adults ≥50 yr and ≈90% efficacy in older age groups; protection sustained ≤8 yr with no booster currently needed; despite high efficacy, only ≈18% of eligible adults ≥50 yr had received 2 doses as of 2022; recent data suggest vaccination is associated with decreased risk for cardiovascular disease, stroke, and dementia, possibly related to preventing varicella-zoster virus reactivation effects

Tdap vaccine and pertussis resurgence: adult formulation contains tetanus toxoid, reduced-dose diphtheria, and reduced-dose acellular pertussis antigens; natural and vaccine-induced immunity to pertussis wanes over time, leading to cyclic outbreaks; 2024 saw approximately 5-fold increase in pertussis cases compared with 2023; acellular pertussis vaccines are effective but protection is time-limited; pertussis rates remain much lower than pre-vaccine era, and breakthrough infections in vaccinated children are less severe; adult recommendations: routine vaccination at age 11 to 12 yr; at least one dose for adults if not previously received; can be given every 10 yr with tetanus booster

Tdap in pregnancy: recommended in every pregnancy regardless of interval between pregnancies; vaccination produces high maternal antibody levels that transfer to infant; provides high levels of infant protection especially during the first 3 mo when risk is highest, extending to ≈6 mo; infant pertussis rates have decreased since pregnancy vaccination program began, despite suboptimal vaccination coverage of ≈55%; prenatal Tdap vaccination is more effective than cocooning strategy (vaccinating family members around newborn)

Human papillomavirus (HPV) vaccine: single formulation (9-valent) is currently available in the United States; no changes to cervical cancer screening recommendations based on vaccination status, though future modifications are possible given high vaccine efficacy; routine adolescent vaccine requiring only 2 doses if started before age 15 yr; if started at age ≥15 yr, 3 doses required; routine vaccination is recommended through age 26 yr; vaccination can be considered for adults aged 27 to 45 yr, though benefit is limited after HPV exposure; early vaccination is critical for maximum benefit; vaccine is highly effective at decreasing HPV infection with evidence of herd immunity; HPV vaccine uptake lags behind other adolescent vaccines and further declined during the COVID-19 pandemic

Hepatitis B vaccines: newer options—HEPLISAV-B is adjuvanted vaccine given as 2-dose series (rather than traditional 3 doses); demonstrates higher response rates in vaccine nonresponders and those at higher risk for nonresponse; PreHevbrio is another new hepatitis B vaccine with higher response rates than traditional comparator but requires 3-dose series; newer vaccines should be considered for populations with lower expected response to traditional hepatitis B vaccines

Monkeypox (MPOX ): new Clade 1 lineage circulating in the US as of early 2025, first identified in Southern California; Clade 1 may cause more severe disease than Clade 2, which caused 2022 US outbreak; vaccines are available for at-risk populations, primarily men who have sex with men and transgender women who have sex with men; 2-dose series provides complete protection; many high-risk individuals already vaccinated from 2022 outbreak; vaccines readily available, though may require public health site access

Practical considerations for vaccine side effects: for patients experiencing significant reactions to COVID-19 vaccines, Novavax (available at Costco and other locations) may be an alternative, and new Moderna MNEX spike uses lower dose and may produce fewer side effects; for influenza vaccines, alternatives to high-dose formulations include adjuvanted Fluad or recombinant Flublok if patients experience severe reactions; for Shingrix, second dose provides longer-lasting protection but decision to complete series after severe first-dose reaction is personal; even if second dose is delayed beyond 6 mo, no need to restart series; for patients with severe reactions, timing vaccination when patient can rest may be advisable

Readings

Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Winston was recorded at the Primary Care Medicine: Principles and Practice 2025, held on October 22-24, 2025, in San Francisco, CA, and presented by University of California, San Francisco. For information about upcoming CME activities from this presenter, please visit https://virtualce.ucsf.edu. Audio Digest thanks Dr. Winston and University of California, San Francisco for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

Lecture ID:

IM730801

Qualifies for:

ABIM MOC, Infectious Disease, Clinical Pharmacology

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.