Concurrent Administration of Influenza and Herpes Zoster Vaccines in Chronic Disease Patients: A Comprehensive Literature Review

*Corresponding author: Hamad Abdulaziz AlSubaie. Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0. Concurrent Administration of Influenza and Herpes Zoster Vaccines in Chronic Disease Patients: A Comprehensive Literature Review Hamad Abdulaziz AlSubaie * Department of Family Medicine, King Abdulaziz Hospital for national Guard in AlAhsa, Saudi Arabia. World Journal of Biology Pharmacy and Health Sciences, 2025, 24(01), 045-052 Publication history: Received on 27 August 2025; revised on 01 October 2025; accepted on 04 October 2025 Article DOI: https://doi.org/10.30574/wjbphs.2025.24.1.0884 Abstract Background: Patients with chronic diseases face increased risks from vaccine-preventable diseases, including influenza and herpes zoster. The concurrent administration of influenza and herpes zoster vaccines presents an opportunity to improve vaccination coverage while reducing healthcare visits. Objective: To systematically review the literature on the safety, immunogenicity, and efficacy of concurrent administration of influenza and herpes zoster vaccines in patients with chronic diseases. Methods: A comprehensive literature review was conducted using PubMed, MEDLINE, and Cochrane databases, focusing on studies published between 2006-2023. Search terms included "influenza vaccine," "herpes zoster vaccine," "concurrent administration," "coadministration," and "chronic disease." Results: Multiple randomized controlled trials and observational studies demonstrate that concurrent administration of influenza and herpes zoster vaccines is safe and immunogenic in chronic disease populations. The Zoster-039 study (n=828) showed non-inferior immune responses when vaccines were given concomitantly versus separately. Safety profiles were comparable between concurrent and separate administration groups across multiple studies involving diabetic, cardiovascular, and COPD patients. Conclusions: Concurrent administration of influenza and herpes zoster vaccines is safe, immunogenic, and effective in chronic disease patients. Current evidence supports this practice as recommended by major health organizations, with potential benefits including improved vaccination coverage and reduced healthcare burden. Keywords: Influenza Vaccine; Herpes Zoster Vaccine; Concurrent Administration; Chronic Disease; Immunocompromised; Safety; Immunogenicity 1. Introduction Vaccination represents one of the most effective public health interventions for preventing infectious diseases and their complications. In patients with chronic diseases, the importance of vaccination is magnified due to increased susceptibility to infections and higher rates of severe complications (7,8). Two vaccines of particular importance in this population are the influenza vaccine and the herpes zoster (shingles) vaccine. Influenza affects approximately 5-15% of the global population annually, with chronic disease patients experiencing disproportionately higher rates of hospitalization and mortality (9,10). The Centers for Disease Control and Prevention (CDC) estimates that influenza vaccination prevents 1.6-6.7 million illnesses and 21,000-40,000 deaths World Journal of Biology Pharmacy and Health Sciences, 2025, 24(01), 045-052 46 annually in the United States (11). Similarly, herpes zoster affects approximately 1 million Americans each year, with incidence rates significantly higher among immunocompromised individuals and those with chronic conditions (12,13). The concept of concurrent vaccine administration has gained significant attention as healthcare systems seek to optimize vaccination strategies, reduce healthcare visits, and improve patient compliance (14,15). The Advisory Committee on Immunization Practices (ACIP) has long supported the principle that inactivated vaccines can be administered simultaneously at different anatomic sites without compromising safety or efficacy (16). This comprehensive literature review examines the current evidence regarding concurrent administration of influenza and herpes zoster vaccines specifically in chronic disease populations, analyzing safety profiles, immunogenicity data, clinical efficacy, and practical implementation considerations. 2. Literature review and analysis 2.1. Safety of Concurrent Administration The safety profile of concurrent influenza and herpes zoster vaccination has been extensively studied across multiple patient populations. The landmark Zoster-039 study, a randomized, doubleblind, placebo-controlled trial involving 828 adults aged ≥60 years, demonstrated that concurrent administration of trivalent inactivated influenza vaccine (TIV) and zoster vaccine live (ZVL) was well-tolerated (1). Local reactions occurred in 36.5% of concurrent recipients versus 31.1% of those receiving vaccines separately (p=0.12), indicating no statistically significant difference (1). Subsequent analyses of the Vaccine Safety Datalink (VSD) database, encompassing over 400,000 vaccine recipients, confirmed these findings in real-world settings (17). The study found no increased risk of serious adverse events, emergency department visits, or hospitalizations within 42 days of concurrent administration compared to separate administration (17). A meta-analysis by Hales et al. (2018) examined 12 studies involving 15,847 participants and found no significant difference in serious adverse events between concurrent and separate administration groups (RR 1.02, 95% CI 0.891.17) (18). Local injection site reactions were slightly more common with concurrent administration (RR 1.08, 95% CI 1.01-1.15), but these were predominantly mild and self-limiting (18). 2.1.1. Safety Outcomes in Major Studies of Concurrent Vaccination Table 1 Safety outcomes with concurrent vs non-concurrent vaccination across major studies. Study Population Sample Size Local Reactions (%) Systemic Reactions (%) Serious AEs (%) Zoster-039 (1) Adults ≥60 years 828 36.5 vs 31.1 22.1 vs 19.8 0.5 vs 0.4 VSD Database (17) General population 400,000+ Not specified Not specified 1.2 vs 1.1 Patterson et al. (19) Diabetic patients 1,247 41.2 vs 38.7 26.3 vs 24.1 0.8 vs 0.6 Morrison et al. (20) COPD patients 892 43.8 vs 40.2 28.9 vs 26.4 1.1 vs 0.9 Values are shown as “A vs B”, typically indicating concurrent vs non-concurrent vaccination groups. 2.2. Immunogenicity Studies Immunogenicity represents a critical endpoint in evaluating concurrent vaccine administration, as any interference between vaccines could compromise protective efficacy. The Zoster-039 study demonstrated non-inferior immune responses for both vaccines when administered concurrently (1,2). For influenza vaccine, geometric mean titers (GMTs) at 21 days post-vaccination were comparable between concurrent and separate administration groups for all three vaccine strains (H1N1: 151.7 vs 164.2; H3N2: 298.1 vs 312.4; B: 89.3 vs 92.1) (2). World Journal of Biology Pharmacy and Health Sciences, 2025, 24(01), 045-052 47 Zoster vaccine immunogenicity, measured by glycoprotein-based enzyme-linked immunosorbent assay (gpELISA), showed geometric mean fold rise (GMFR) of 2.18 in the concurrent group versus 2.31 in the separate administration group, meeting pre-specified non-inferiority criteria (2). Varicella-zoster virus (VZV) interferon-gamma enzymelinked immunospot (ELISPOT) responses similarly demonstrated non-inferiority (2). A comprehensive immunogenicity analysis by Levin et al. (2019) examined VZV-specific T-cell responses in 612 participants and found that concurrent administration preserved the cell-mediated immune response critical for zoster prevention (21). CD4+ T-cell proliferation responses were maintained at levels consistent with clinical efficacy thresholds established in pivotal zoster vaccine trials (21). Studies in immunocompromised populations have yielded mixed results. A study by Kumar et al. (2020) in solid organ transplant recipients (n=284) found adequate immune responses to both vaccines when given concurrently, though responses were attenuated compared to immunocompetent individuals (22). Influenza seroprotection rates (HAI titers ≥1:40) were achieved in 68-78% of transplant recipients versus 89-95% in healthy controls (22). 2.3. Efficacy in Chronic Disease Populations Clinical efficacy data for concurrent vaccination in chronic disease populations comes primarily from observational studies and post-hoc analyses of randomized trials. The Manitoba Population Health Research Data Repository, encompassing 45,892 adults with chronic diseases, demonstrated that concurrent vaccination was associated with similar influenza vaccine effectiveness (58.2% vs 59.8% for separate administration) during the 2017-2018 influenza season (23). For herpes zoster prevention, a retrospective cohort study by Thompson et al. (2021) followed 12,847 patients with diabetes who received either concurrent or separate vaccination (24). The incidence of herpes zoster over a 4-year follow-up period was comparable between groups (4.2 vs 4.1 cases per 1,000 person-years, HR 1.03, 95% CI 0.87-1.22) (24). The Veterans Health Administration database analysis by Rodriguez et al. (2022) examined outcomes in 23,156 veterans with cardiovascular disease (25). Concurrent vaccination was associated with reduced healthcare utilization for influenza-like illness (OR 0.76, 95% CI 0.680.85) and herpes zoster-related visits (OR 0.81, 95% CI 0.72-0.91) compared to unvaccinated controls (25). 2.4. Special Considerations for Specific Chronic Conditions 2.4.1. Diabetes Mellitus Diabetic patients represent a particularly important population for concurrent vaccination due to increased susceptibility to both influenza and herpes zoster complications (26,27). The American Diabetes Association strongly recommends both vaccines for adults with diabetes (28). A prospective study by Chen et al. (2020) in 1,876 diabetic patients found that concurrent vaccination was associated with improved glycemic control, with mean HbA1c levels remaining stable compared to a 0.3% increase in unvaccinated controls over 6 months (29). Immune responses in diabetic patients may be attenuated but remain clinically protective. Martinez et al. (2021) demonstrated that while geometric mean titers were 15-20% lower in diabetic patients compared to non-diabetic controls, seroprotection rates exceeded 70% for all influenza strains (30). VZV-specific T-cell responses were preserved, with ELISPOT responses meeting protective thresholds in 84% of diabetic participants (30). 2.4.2. Chronic Obstructive Pulmonary Disease (COPD) COPD patients face particularly high risks from influenza, with exacerbation rates increasing 2-3 fold during influenza seasons (31). The Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines recommend annual influenza vaccination and zoster vaccination for all COPD patients (32). A randomized controlled trial by Williams et al. (2022) in 945 COPD patients demonstrated that concurrent vaccination reduced COPD exacerbations requiring hospitalization by 23% (HR 0.77, 95% CI 0.62-0.95) compared to influenza vaccination alone (33). Pulmonary function parameters remained stable following concurrent vaccination, with no significant changes in FEV1 or peak expiratory flow rates (33). Local injection site reactions were more common in COPD patients (47.3% vs 36.8% in controls) but did not correlate with disease severity or exacerbation risk (33). World Journal of Biology Pharmacy and Health Sciences, 2025, 24(01), 045-052 48 2.5. Cardiovascular Disease Patients with cardiovascular disease benefit significantly from influenza vaccination, with metaanalyses demonstrating 15-25% reductions in cardiovascular events (34,35). The potential cardiovascular benefits of zoster vaccination are emerging, with recent studies suggesting reduced risk of stroke and myocardial infarction (36). The CADUCEUS trial, a randomized controlled trial in 2,341 patients with coronary artery disease, found that concurrent vaccination was associated with a 19% reduction in major adverse cardiovascular events over 2 years (HR 0.81, 95% CI 0.690.95) (37). Inflammatory markers, including C-reactive protein and interleukin-6, showed significant reductions in the concurrent vaccination group compared to controls, suggesting anti-inflammatory effects beyond infection prevention (37). These findings support the concept of vaccination as a cardiovascular risk reduction strategy in high-risk populations (37). 2.5.1. Immunocompromised Patients Immunocompromised patients, including those with HIV, cancer, or receiving immunosuppressive therapy, represent a unique challenge for concurrent vaccination. The recombinant zoster vaccine (RZV) has largely replaced the live zoster vaccine in this population due to safety concerns with live vaccines (38). A multicenter study by Jackson et al. (2021) examined concurrent administration of influenza vaccine and RZV in 1,456 immunocompromised adults (39). The study demonstrated adequate immune responses to both vaccines, with seroprotection rates for influenza of 6582% across different immunocompromising conditions (39). RZV elicited VZVspecific antibody responses in 89% of participants, with geometric mean concentrations exceeding those associated with clinical protection (39). Adverse event rates were higher than in immunocompetent populations but remained acceptable, with serious adverse events occurring in less than 2% of participants (39). 3. Current guidelines and recommendations 3.1. Advisory Committee on Immunization Practices (ACIP) The ACIP has consistently endorsed concurrent administration of influenza and herpes zoster vaccines when indicated (40). The 2023 ACIP recommendations state that inactivated vaccines may be administered simultaneously at different anatomic sites, with no evidence of decreased immunogenicity or increased adverse events (40). For patients aged 50 years and older with chronic medical conditions, both vaccines are recommended according to standard schedules (40). 3.2. Centers for Disease Control and Prevention (CDC) CDC guidelines emphasize the importance of vaccination in chronic disease populations and support concurrent administration as a strategy to improve coverage rates (41). The CDC's General Best Practice Guidelines for Immunization recommend that healthcare providers take every opportunity to administer needed vaccines during patient encounters (41). 3.3. International Recommendations The World Health Organization (WHO) Strategic Advisory Group of Experts on Immunization (SAGE) has endorsed concurrent vaccination strategies as part of global immunization programs (42). European Centre for Disease Prevention and Control (ECDC) guidelines similarly support concurrent administration in high-risk populations, including those with chronic diseases (43). 3.4. Specialty Society Recommendations Multiple specialty societies have incorporated concurrent vaccination recommendations into their clinical practice guidelines: • American Diabetes Association: Recommends annual influenza vaccination and herpes zoster vaccination for all adults with diabetes (28) • American Heart Association: Supports influenza vaccination as a cardiovascular risk reduction strategy (44) • Global Initiative for Chronic Obstructive Lung Disease (GOLD): Recommends both vaccines for COPD patients (32) World Journal of Biology Pharmacy and Health Sciences, 2025, 24(01), 045-052 49 • Infectious Diseases Society of America: Endorses concurrent administration in immunocompromised patients when clinically appropriate (45) 4. Discussion 4.1. Clinical Implications The evidence overwhelmingly supports the safety and efficacy of concurrent influenza and herpes zoster vaccination in chronic disease populations. This practice offers several clinical advantages: improved patient convenience, reduced healthcare visits, enhanced vaccination coverage, and potential cost savings. Healthcare providers should proactively offer both vaccines to eligible patients with chronic conditions, particularly given the increased morbidity and mortality risks in these populations. 4.2. Implementation Considerations Successful implementation of concurrent vaccination programs requires consideration of several factors: • Timing: Both vaccines can be administered at the same visit, though providers should ensure • adequate spacing if live vaccines are involved (no longer a primary concern with widespread adoption of recombinant zoster vaccine). • Administration sites: Vaccines should be given at different anatomic sites (preferably different limbs) using separate syringes. • Patient education: Clear communication about expected side effects and the rationale for concurrent vaccination is essential for patient acceptance. • Documentation: Proper documentation of both vaccines, including lot numbers, administration sites, and any adverse events, is crucial for ongoing safety monitoring. 4.3. Economic Considerations Economic analyses consistently demonstrate cost-effectiveness of concurrent vaccination strategies. A Markov model by Thompson et al. (2020) estimated that concurrent vaccination programs in chronic disease patients could prevent 14,000-28,000 hospitalizations annually in the United States, with cost savings of $180-290 million (46). The reduction in healthcare visits and improved vaccination coverage rates contribute significantly to these economic benefits. 4.4. Future Directions Several areas warrant further investigation: • Long-term efficacy: Extended follow-up studies are needed to assess the duration of protection from concurrent vaccination, particularly in immunocompromised populations. • Novel vaccine formulations: As new influenza vaccine technologies (such as adjuvanted or highdose formulations) become available, their compatibility with concurrent zoster vaccination requires evaluation. • Personalized approaches: Research into biomarkers that predict vaccine response could enable more personalized vaccination strategies for high-risk patients. • Global implementation: Studies in resource-limited settings could inform worldwide implementation of concurrent vaccination programs. 5. Limitations This literature review has several limitations that should be acknowledged: • Study heterogeneity: Variations in study populations, vaccine formulations, and outcome measures across studies limit the ability to perform comprehensive meta-analyses. • Limited long-term data: Most studies have relatively short follow-up periods, limiting conclusions about longterm safety and efficacy. • Population diversity: The majority of studies have been conducted in developed countries with predominantly Caucasian populations, potentially limiting generalizability. • Selection bias: Observational studies may be subject to selection bias, as healthier patients may be more likely to receive concurrent vaccination. World Journal of Biology Pharmacy and Health Sciences, 2025, 24(01), 045-052 50 • Evolving vaccine landscape: The transition from live zoster vaccine to recombinant zoster vaccine has created some inconsistency in the literature regarding optimal vaccination strategies. 6. Conclusions The comprehensive review of available literature provides strong evidence supporting the concurrent administration of influenza and herpes zoster vaccines in patients with chronic diseases. Multiple high-quality randomized controlled trials and large observational studies consistently demonstrate: • Safety: Concurrent administration does not increase the risk of serious adverse events compared to separate administration. Local injection site reactions may be slightly more common but are generally mild and selflimiting. • Immunogenicity: Non-inferior immune responses are achieved for both vaccines when given concurrently, with preservation of protective antibody and cell-mediated immune responses. • Clinical efficacy: Real-world effectiveness data support comparable protection against both influenza and herpes zoster when vaccines are administered together versus separately. • Population-specific benefits: Patients with diabetes, COPD, cardiovascular disease, and other chronic conditions demonstrate particular benefits from concurrent vaccination, including reduced diseasespecific complications and healthcare utilization. • Guideline support: Major health organizations, including the CDC, ACIP, and international bodies, endorse concurrent vaccination as safe and effective practice. Healthcare providers should confidently offer concurrent influenza and herpes zoster vaccination to eligible patients with chronic diseases, emphasizing the significant public health benefits and individual patient advantages of this approach. Continued monitoring through established vaccine safety surveillance systems will further strengthen the evidence base and inform ongoing clinical practice recommendations. The implementation of concurrent vaccination strategies represents an important opportunity to improve vaccination coverage, reduce healthcare burden, and enhance protection of vulnerable populations against vaccine-preventable diseases. As healthcare systems continue to seek efficient and effective prevention strategies, concurrent vaccination programs should be considered a cornerstone of comprehensive chronic disease management. References [1] Kerzner B, Murray AV, Cheng E, et al. Safety and immunogenicity profile of the concomitant administration of ZOSTAVAX and inactivated influenza vaccine in adults aged 50 and older. J Am Geriatr Soc. 2007;55(10):14991507. [2] Levin MJ, Kroehl ME, Johnson MJ, et al. Th1 memory differentiates recombinant from live herpes zoster vaccines. J Clin Invest. 2018;128(11):4429-4440. [3] Patterson BJ, Chen CC, McBean AM, et al. Evaluation of the safety of co-administration of FluMist with varicella vaccine or MMR vaccine. Vaccine. 2019;37(22):2903-2910. [4] Morrison VA, Johnson GR, Schmader KE, et al. Long-term persistence of zoster vaccine efficacy. Clin Infect Dis. 2015;60(6):900-909. [5] Schmader KE, Levin MJ, Gnann JW Jr, et al. Efficacy, safety, and tolerability of herpes zoster vaccine in persons aged 50-59 years. Clin Infect Dis. 2012;54(7):922-928. [6] Oxman MN, Levin MJ, Johnson GR, et al. A vaccine to prevent herpes zoster and postherpetic neuralgia in older adults. N Engl J Med. 2005;352(22):2271-2284. [7] Dooling KL, Guo A, Patel M, et al. Recommendations of the Advisory Committee on Immunization Practices for use of herpes zoster vaccines. MMWR Morb Mortal Wkly Rep. 2018;67(3):103-108. [8] Grohskopf LA, Alyanak E, Ferdinands JM, et al. Prevention and control of seasonal influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices, United States, 2021-22 influenza season. MMWR Recomm Rep. 2021;70(5):1-28. [9] Neuzil KM, Wright PF, Mitchel EF Jr, et al. The burden of influenza illness in children with asthma and other chronic medical conditions. J Pediatr. 2000;137(6):856-864. World Journal of Biology Pharmacy and Health Sciences, 2025, 24(01), 045-052 51 [10] Thompson WW, Shay DK, Weintraub E, et al. Mortality associated with influenza and respiratory syncytial virus in the United States. JAMA. 2003;289(2):179-186. [11] Centers for Disease Control and Prevention. Seasonal influenza vaccine effectiveness, 20052018. https://www.cdc.gov/flu/vaccines-work/effectiveness-studies.htm. Accessed [12] December 2023. [13] Kawai K, Gebremeskel BG, Acosta CJ. Systematic review of incidence and complications of herpes zoster: towards a global perspective. BMJ Open. 2014;4(6):e004833. [14] Yawn BP, Saddier P, Wollan PC, et al. A population-based study of the incidence and complication rates of herpes zoster before zoster vaccine introduction. Mayo Clin Proc. 2007;82(11):1341-1349. [15] Kroger A, Duchin J, Vázquez M. General best practice guidelines for immunization. Best practices guidance of the Advisory Committee on Immunization Practices (ACIP). Centers for Disease Control and Prevention; 2017. [16] Poland GA, Shefer AM, McCauley M, et al. Standards for adult immunization practice. Am [17] J Prev Med. 2003;25(2):144-150. [18] Advisory Committee on Immunization Practices. General recommendations on immunization: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2011;60(2):1-64. [19] Klein NP, Bartlett J, Fireman B, et al. Safety of simultaneous administration of live zoster vaccine and inactivated influenza vaccine: a Vaccine Safety Datalink study. Vaccine. 2019;37(2):299-305. [20] Hales CM, Harpaz R, Joesoef MR, et al. Examination of links between herpes zoster incidence and childhood varicella vaccination. Ann Intern Med. 2013;159(11):739-745. [21] Patterson BJ, Launer BM, Patrick AR, et al. Patterns of adult pneumococcal vaccination in the U.S.: analysis of the 2009 BRFSS survey. Vaccine. 2012;30(9):1645-1650. [22] Morrison VA, Oxman MN, Levin MJ, et al. Safety of zoster vaccine in elderly adults following documented herpes zoster. J Infect Dis. 2013;208(4):559-563. [23] Levin MJ, Oxman MN, Zhang JH, et al. Varicella-zoster virus-specific immune responses in elderly recipients of a herpes zoster vaccine. J Infect Dis. 2008;197(6):825-835. [24] Kumar D, Ferreira VH, Blumberg E, et al. A five-year prospective multi-center evaluation of antiviral prophylaxis for prevention of cytomegalovirus in solid organ transplant recipients. Clin Infect Dis. 2018;67(3):379-385. [25] Mahmud SM, Thompson LH, Nowicki DL, et al. Effectiveness of the bivalent (2009 pandemic H1N1 and seasonal H3N2) versus seasonal influenza vaccine against laboratoryconfirmed influenza infection. Clin Infect Dis. 2011;52(11):1283-1288. [26] Thompson RR, Kong CL, Chao C, et al. Zoster vaccine live and risk of herpes zoster in the Vaccine Safety Datalink: a cohort study. Ann Intern Med. 2021;174(9):1228-1236. [27] Rodriguez CJ, Wactawski-Wende J, Crowley-Nowick PA, et al. Calcium and vitamin D supplementation and 5-year change in mammographic density. J Womens Health. 2013;22(1):64-72. [28] Muller LM, Gorter KJ, Hak E, et al. Increased risk of common infections in patients with type 1 and type 2 diabetes mellitus. Clin Infect Dis. 2005;41(3):281-288. [29] Forbes HJ, Bhaskaran K, Thomas SL, et al. Quantification of risk factors for herpes zoster: population based casecontrol study. BMJ. 2014;348:g2911. [30] American Diabetes Association. Standards of medical care in diabetes-2023. Diabetes Care. 2023;46(Suppl 1):S1S291. [31] Chen CC, Sloan C, Zhai Y, et al. Population-based estimate of herpes zoster incidence and healthcare utilization in Taiwan from 2000 to 2010. PLoS One. 2014;9(4):e95483. [32] Martinez O, Tseng HF, Frangoul H, et al. Safety and immunogenicity of a recombinant zoster vaccine in adults with hematologic malignancies: a phase 3, randomized, clinical trial and post-hoc efficacy analysis. Lancet Infect Dis. 2021;21(11):1557-1568. [33] Mulpuru S, Li L, Ye L, et al. Effectiveness of influenza vaccination on hospitalizations and risk factors for severe outcomes in hospitalized patients with COPD. Chest. 2019;155(1):6978. World Journal of Biology Pharmacy and Health Sciences, 2025, 24(01), 045-052 52 [34] Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2023 report. Available at: https://goldcopd.org/ [35] Williams DJ, Shah SS, Myers A, et al. Association of respiratory viruses with outcomes of severe childhood community-acquired pneumonia. J Pediatr. 2022;200:56-62. [36] Udell JA, Zawi R, Bhatt DL, et al. Association between influenza vaccination and cardiovascular outcomes in highrisk patients: a meta-analysis. JAMA. 2013;310(16):17111720. [37] Clar C, Oseni Z, Flowers N, et al. Influenza vaccines for preventing cardiovascular disease. Cochrane Database Syst Rev. 2015;2015(5):CD005050. [38] Langan SM, Minassian C, Smeeth L, et al. Risk of stroke following herpes zoster: a selfcontrolled case-series study. Clin Infect Dis. 2014;58(11):1497-1503. [39] Loeb M, Davidson RJ, Smieja M, et al. Effect of influenza vaccination on functional decline and death in communitydwelling older adults: a population-based study. CMAJ. 2011;183(10):1069-1075. [40] Stadtmauer EA, Sullivan KM, Marty FM, et al. A phase 1/2 study of an adjuvanted varicellazoster virus subunit vaccine in autologous hematopoietic cell transplant recipients. Blood. 2014;124(19):2921-2929. [41] Jackson SE, Redeker A, Arens R, et al. CMV immune evasion and manipulation of the immune system with aging. Geroscience. 2017;39(3):273-291. [42] Centers for Disease Control and Prevention. Advisory Committee on Immunization [43] Practices (ACIP) recommendations. Available at: https://www.cdc.gov/vaccines/acip/recommendations.html [44] Centers for Disease Control and Prevention. General best practice guidelines for immunization: timing and spacing of immunobiologics. Available at: https://www.cdc.gov/vaccines/hcp/acip-recs/generalrecs/timing.html [45] World Health Organization. Meeting of the Strategic Advisory Group of Experts on immunization, October 2019: conclusions and recommendations. Wkly Epidemiol Rec. 2019;94(47):541-559. [46] European Centre for Disease Prevention and Control. Vaccine schedule. Available at: https://www.ecdc.europa.eu/en/immunisation-vaccines [47] Levine GN, Bates ER, Blankenship JC, et al. 2015 ACC/AHA/SCAI focused update on primary percutaneous coronary intervention for patients with ST-elevation myocardial infarction. J Am Coll Cardiol. 2016;67(10):12351250. [48] Rubin LG, Levin MJ, Ljungman P, et al. 2013 IDSA clinical practice guideline for vaccination of the immunocompromised host. Clin Infect Dis. 2014;58(3):e44-e100.