Developing a Latin American Delphi Consensus on Vaccination for Respiratory Diseases in Older Adults

Study Design

This study utilized a modified Delphi (e-Delphi) methodology with two rounds of electronic surveys to gather expert input and achieve consensus on solutions to complex problems. This approach synthesizes insights from specialists to address specific issues effectively. This study was conducted using a two-round Delphi consensus, focusing on the adoption of vaccination recommendations for older adults in LAC. The Delphi methodology was chosen for its effectiveness in building consensus on public health and vaccination topics in vulnerable populations.12,28)

In the first round, which took place between July 23, 2024, and August 13, 2024, 35 participating experts were asked to evaluate each recommendation on a scale from 1 to 5, with 1 being the lowest score and 5 the highest. Access to the data was obtained immediately after the conclusion of the first round on August 13, 2024. Recommendations were considered accepted when at least 80% of the experts scored them with a 4 or 5. This threshold was selected based on previous Delphi-based studies that use 70%–80% as acceptable consensus levels, depending on the topic and required rigor of agreement. A stricter threshold was chosen due to the public health relevance of the recommendations.29,30) Recommendations that did not meet this threshold proceeded to a second round, which took place between August 24, 2024, and September 4, 2024. Access to the second-round data was obtained immediately after its conclusion on September 4, 2024.

Selection of Participants

Geriatricians who are members of the Academia Latinoamericana de Medicina del Adulto Mayor (ALMA), a non-profit organization established in 2002 to enhance healthcare for older adults in the region, were invited to participate.12,31) In addition, infectious disease specialists, pulmonologists, pediatricians, and immunologists recommended by ALMA geriatricians were also invited.

Participants were selected based on their expertise, professional reputation, and involvement in research or clinical practice related to vaccination, immunization, and geriatrics. Ideal participants were those who had published peer-reviewed research papers in these fields within the past 5 years or possessed a minimum of 10 years of experience. To ensure diverse perspectives and comprehensive representation, the panel included clinicians, academic researchers, and educators with specific expertise in vaccination, immunization, and geriatrics. This approach aimed to reflect the broad range of knowledge required to address the complex challenges associated with immunization in older adults.

Search Strategy and Development of Statements

To establish the recommendations and statements, a rapid evidence review was conducted in PubMed and Scopus, covering all records from inception to May 18, 2024, and including results published in English, Spanish and Portuguese. We searched using a prespecified strategy that combined terms for older adults, vaccination, the five target pathogens (influenza, Streptococcus pneumoniae, COVID-19, RSV, pertussis), and guidance document types (guideline, recommendation, consensus, position statement, technical report).28,31,32) We included documents with explicit immunization recommendations for adults aged 60 years or older, or for risk groups that include older adults, relevant to LAC or international guidance applicable to the region. We excluded records without explicit recommendations, those outside the five target diseases, pediatric-only documents, and duplicates. This process resulted in a list of 20 statements, distributed across the five diseases. An open-ended question was also included to allow experts to provide observations and feedback. Participants had 3 weeks to respond to the first round and 2 weeks to complete the second round, with weekly reminders sent to improve the response rate. The survey was conducted in Spanish.

Additionally, well-known clinical practice guideline repositories were consulted, such as Trip Database, Canadian Medical Association Infobase, EGuidelines, the Guidelines International Network (G-I-N), the National Guideline Clearinghouse, and the National Health and Medical Research Council (NHMRC). Guidelines from organizations such as the National Institute for Health and Care Excellence (NICE), Mexico’s National Center for Health Technology Excellence (Centro Nacional de Excelencia Tecnológica en Salud, CENETEC), GuíaSalud, and Colombia’s Ministry of Health and Social Protection (MINSALUD) were also considered.12,33,34) Furthermore, documents with similar characteristics from portals of the WHO, the Pan American Health Organization (PAHO), and geriatric and gerontology-related organizations, such as the Spanish Society of Geriatrics and Gerontology and the International Federation on Ageing (IFA), were included.

Delphi Rounds

The Delphi consensus consisted of two rounds aimed at reaching an agreement on vaccination recommendations for older adults. In the first round, which took place between July 23, 2024, and August 13, 2024, 35 participating experts were asked to evaluate each recommendation on a scale from 1 to 5, with 1 being the lowest score and 5 the highest. Recommendations were considered accepted if they received a score of 4 or higher from at least 80% of the evaluators. Recommendations that did not meet this threshold proceeded to a second round, which took place between August 24, 2024, and September 4, 2024, where the same criterion of 80% of evaluators assigning a score of 4 or 5 was applied for final acceptance.29,30,35)

Demographic and Academic Variables

In addition to evaluating the recommendations, the experts were asked to provide information about their medical specialty and academic degrees. The variables included: (1) medical specialty, (2) whether they held a master’s or doctoral degree and the field of that degree, and (3) whether they were involved in university teaching. This information enabled a better characterization of the profile of the participating experts and allowed for an assessment of the diversity of perspectives within the consensus.31,33,34)

Ethical Approval

All experts who participated in the Delphi consensus provided informed consent for the use of their opinions in the development of this manuscript. The project was registered with the Dirección General de Investigación, Desarrollo e Innovación of the Universidad Científica del Sur under the registration code PI-15-2024-0501 and was granted an exemption from ethical approval.

Participant Characteristics

The Delphi consensus included 35 specialists from various related medical fields, distributed as follows: 18 geriatricians, 6 infectious disease specialists, 6 pulmonologists, 1 family physician, 1 otolaryngologist, 1 pediatric vaccine expert, and 2 pediatric immunologists. Among the participants, 18 held a master’s degree, and 5 had a doctoral degree. Additionally, 30 of the specialists reported being engaged in university teaching. Similarly, 7 specialists were from Peru, while 5 were from Brazil and Mexico, respectively (Table 1).

Table 1.

Characteristics of participants in the Delphi consensus

Recommendations Accepted in the Second Round

In the second round of the Delphi consensus, recommendations for each disease met the prespecified consensus threshold (≥80% of ratings at 4 or 5 on a 1–5 scale). Of the 20 statements evaluated in Round 1, 15 reached consensus, 2 were removed as redundant, and 3 were revised and then reached consensus in Round 2, yielding 18 final accepted recommendations (Fig. 1). The disposition of all statements across rounds is shown in Supplementary Table S3, and the full score distributions for each statement in Rounds 1 and 2 are provided in Supplementary Tables S1 and S2, respectively. In addition, the evidence selection flow is summarized in the flowchart in Supplementary Fig. S1.

Fig. 1.

Flowchart of the process and methodology.

Pertussis (Whooping cough)

It was recommended that adults receive a Tdap (tetanus, diphtheria, and pertussis) or Td (tetanus and diphtheria) booster every 10 years to maintain adequate immunity levels. For older adults aged 65 and over, a Tdap dose was recommended if they had not received one in the past 10 years, given the higher morbidity associated with pertussis in this age group (Table 2).

Table 2.

Recommendations derived from expert consensus using the Delphi methodology

Synthesis of Open-Ended Panel Feedback

We received 71 open-ended comments. Most focused on dosing and timing and on eligibility criteria; fewer raised implementation points. By disease, for COVID-19 (n=12), panelists asked for clearer intervals, separating the primary series from booster doses. For RSV (n=6), they asked to spell out eligibility by age and noted that it is not an annual vaccine. For pneumococcal disease (n=15), they requested concise guidance on sequencing and schedules and brief notes for high-risk groups. For influenza (n=5), the emphasis was on risk-based eligibility and annual vaccination for adults 65 years and older. For pertussis (n=3), they supported boosters every 10 years and a one-time Tdap for those without prior receipt. Cross-cutting feedback (n=30) asked for consistent terminology, short examples of risk factors, and alignment with national calendars.

Comparison with Previous Studies

Our findings on vaccination recommendations for older adults in LAC are consistent with evidence showing that immunization reduces respiratory disease incidence and severity, functional decline, and healthcare costs in this population. Prior work in LAC underscores influenza’s substantial burden, including mortality and hospitalizations in older adults, and supports the use of high-dose or adjuvanted formulations in adults aged ≥65 years.28) Our consensus aligns with this literature and with guidance permitting coadministration when indicated.36,37)

Our consensus is aligned with major guidance for older adults.36,37) For tetanus–diphtheria–pertussis, it is consistent with adult schedules that include a one-time Tdap followed by decennial boosters.38) Our pneumococcal statements align with the Advisory Committee on Immunization Practices (ACIP) adult recommendations,39) while acknowledging subsequent United States updates that expand PCV eligibility to adults aged ≥50 years.40) To aid implementation in LAC, we prioritize coverage while working toward alignment with current recommendations and identify higher-risk adults—e.g., those with immunocompromise, cerebrospinal fluid leak or cochlear implant, major chronic comorbidities, current smoking, residence in long-term care or other congregate settings, and Indigenous or remote communities with higher disease burden.38,39)

For RSV, our single-dose approach in older adults is consistent with updated recommendations and CDC clinical guidance.41,42)

Influenza, COVID-19, and RSV vaccines can be administered at the same visit, using separate injection sites and with no minimum interval between them.36,37,41,42) In Latin America, influenza seasonality varies—winter peaks in Southern Cone settings and multi-peak or near year-round circulation in tropical areas—so vaccination should be scheduled ahead of the expected local peak or during national campaigns, with coadministration when it facilitates uptake.9,28)

Regarding pertussis, Choi et al.31) and Hozbor et al.33) have identified a resurgence of this disease in older adults, partly attributed to waning immunity over time and low booster coverage in adults. These studies underscore the need for periodic Tdap boosters in adults, particularly those with comorbidities. Our consensus reinforces this recommendation, advocating for Tdap administration every 10 years, especially in adults aged 65 and older, reflecting a strategy aligned with international practices.

Two context-specific COVID-19 points may guide implementation. First, for adults aged 65–74 years, we favored an annual booster with an optional 6-month dose for higher-risk individuals; later, ACIP recommended two 2024–2025 doses for adults aged ≥65 years.43-45) Second, after SARS-CoV-2 infection, vaccination need not be delayed; individuals may consider waiting 3 months from symptom onset or from the first positive test if asymptomatic. Individualized decisions—especially for adults aged 65–74 years—should weigh multimorbidity and frailty, immunocompromise, exposure risk, interval since last vaccine or infection, and local circulation.43-45)

In our Delphi process, three statements (COVID-19 wording on “primary” vs “booster” doses; booster frequency for adults 65–74 with examples of risk factors; and RSV coadministration phrasing aligned with clinical guidance) were revised after Round 1 and subsequently reached consensus in Round 2.40-42) Two additional COVID-19 items were removed as redundant in Round 1.

Relevance of Findings in Public Health

The implementation of appropriate vaccination programs for older adults is critical in LAC, where healthcare systems face a significant burden of respiratory diseases. The PAHO and the WHO have emphasized the importance of increasing vaccination coverage in this group to reduce hospitalizations and deaths, thereby contributing to the sustainability of healthcare systems.46-48)

A previous study highlights that the significant fragmentation and segmentation of Latin American healthcare systems, combined with the lack of stable funding, hinder the effective implementation of immunization strategies for older adults, particularly in rural and low-income areas.49) In this context, general recommendations on vaccination strategies for older adults—such as modified doses, multivalent/adjuvanted formulations, consideration of chronic diseases, multimorbidity, frailty, and adapting strategies to different levels of care—would not suffice when accounting for the heterogeneity of healthcare systems in the region.5)

Moreover, the aging population in LAC, with projections indicating that the percentage of older adults aged 60 and over will double by 2050, highlights the importance of public health planning that incorporates vaccination as a fundamental component.49,50) Vaccination programs against influenza, pneumococcus, COVID-19, and RSV in older adults are not only an individual preventive measure but are also essential for reducing the burden on healthcare systems already operating at full capacity and facing significant financial challenges. Studies, such as that by Atun et al.,47) suggest that the economic benefits of these programs are substantial, reducing hospital costs and the burden of comorbidities in this population. The disability that often arises in older adults following vaccine-preventable diseases increases the caregiving burden, which is typically shouldered by families in LAC.

The approach adopted in this study highlights the need for vaccination policies tailored to the region’s needs and supported by sustained financial commitments. This is crucial for preventing severe and costly complications associated with respiratory diseases in older adults, thereby improving the quality of life for this population and promoting healthy, functional aging.7,50) Vaccination in older adults is recommended as part of a comprehensive package of interventions aimed at optimizing intrinsic capacity and functional ability, enabling well-being in old age. Healthcare professionals, policymakers, communities, and, most importantly, users and caregivers, are key stakeholders in optimizing coverage and ensuring the success of vaccination programs.

Limitations and Strengths

A limitation of this study lies in the Delphi methodology, which, although effective in achieving consensus, may introduce biases by not including all decision-makers from the region, thereby limiting the diversity of perspectives.7,49,50)

Another limitation is the heterogeneity in the healthcare infrastructure across LAC, which could hinder the uniform implementation of the proposed recommendations, given the significant variation in resources and implementation capacity among countries.46,47)

However, this study also has several strengths. The inclusion of experts from multiple disciplines provides a comprehensive approach.7,49,50) This study is particularly relevant due to the creation of a consensus specifically adapted for LAC, offering a framework that could guide future public health policies and programs in the region. By providing evidence-based recommendations for vaccination in older adults, this first consensus represents an excellent opportunity to adapt and implement recommendations aimed at increasing vaccination coverage and reducing the incidence and mortality associated with respiratory diseases in this vulnerable population.7,49,50)

A notable limitation is the lack of studies in the region that incorporate stratification by functional status, frailty, and specific serotypes. This gap hinders a more precise evaluation of immunization outcomes in older adults, particularly in populations with diverse levels of vulnerability. Future research should prioritize addressing these gaps by including stratified analyses based on frailty, functional capacity, and serotype-specific data. Such studies would provide a deeper understanding of vaccine efficacy, safety, and long-term outcomes in older adults, allowing for tailored immunization strategies that better align with the heterogeneity of this population. Our scope was restricted to adult respiratory vaccines (influenza, COVID-19, RSV, pneumococcal, pertussis); other age-relevant vaccines (e.g., zoster, hepatitis B) were outside the scope of this work. Strengthening regional data in these areas is essential to optimize vaccination policies and improve health outcomes in older adults across Latin America.

Conclusion

This study presents the first expert consensus on vaccination strategies for older adults in LAC, offering tailored, evidence-based recommendations to address key respiratory diseases: pertussis, COVID-19, influenza, pneumococcus, and RSV. These strategies aim to reduce preventable infections, improve health outcomes, and support healthy aging in a population facing significant healthcare challenges.

The recommendations highlight the importance of implementing targeted immunization programs for older adults, addressing critical barriers such as healthcare system fragmentation, limited access in rural areas, and financial constraints. These evidence-based statements, developed through expert consensus, provide a framework for improving vaccination coverage and reducing the burden of respiratory diseases in LAC. Achieving these goals requires coordinated action and collaboration among policymakers, healthcare providers, and communities to ensure equitable and effective implementation of vaccination strategies tailored to this vulnerable population.