{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,29]],"date-time":"2026-01-29T02:57:19Z","timestamp":1769655439224,"version":"3.49.0"},"reference-count":48,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T00:00:00Z","timestamp":1769472000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"National Key R&D Program of China","doi-asserted-by":"publisher","award":["2024YFC2310600"],"award-info":[{"award-number":["2024YFC2310600"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]},{"name":"State Key Laboratory of Drug Regulatory Science","award":["2024SKLDRS0209"],"award-info":[{"award-number":["2024SKLDRS0209"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background: Streptococcus pneumoniae (Spn) is a leading bacterial pathogen responsible for severe invasive diseases, including meningitis, sepsis, and pneumonia. Current pneumococcal vaccines, which are all based on capsular polysaccharide antigens, provide limited protection and are further compromised by post-vaccination serotype replacement. Pneumococcal surface protein A (PspA), a highly conserved virulence factor expressed across diverse serotypes, has emerged as a promising candidate antigen for novel protein-based vaccines. However, progress in this field has been hindered by the absence of standardized in vitro functional antibody assays. Methods: This study established a robust functional antibody detection method for PspA-based protein vaccines by modifying the conventional multiplex opsonophagocytic killing assay (MOPA), originally designed for polysaccharide-based vaccines. Using polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) typing, a target strain panel was selected and developed to include representative strains from PspA Family 1-Clade 2 and Family 2-Clades 3 and 4. The MOPA protocol was optimized by extending the phagocytic reaction time to enhance sensitivity. Specificity was confirmed through recombinant PspA competitive inhibition assays. Results: The assay demonstrated high linearity (R2 \u2265 0.98) between opsonophagocytic index (OI) and serum dilution, along with acceptable repeatability (CV \u2264 30%) and intermediate precision (CV \u2264 50%). Both preclinical and clinical serum samples exhibited potent bactericidal activity against diverse PspA families, independent of capsule type. Conclusions: This study provided a standardized framework to support the development and regulatory assessment of protein-based pneumococcal vaccines.<\/jats:p>","DOI":"10.3390\/vaccines14020127","type":"journal-article","created":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T15:41:56Z","timestamp":1769528516000},"page":"127","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Development and Validation of a Functional Antibody Assay for Evaluating Protein-Based Pneumococcal Vaccines"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0009-0005-5936-038X","authenticated-orcid":false,"given":"Jiangjiao","family":"Li","sequence":"first","affiliation":[{"name":"State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing 102629, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kang","family":"Li","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing 102629, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Youyou","family":"Wang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing 102629, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yang","family":"Huang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing 102629, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiuwen","family":"Sui","sequence":"additional","affiliation":[{"name":"CanSino Biologics Research Center, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xiao","family":"Xu","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing 102629, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Huijing","family":"Du","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing 102629, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bochao","family":"Wei","sequence":"additional","affiliation":[{"name":"CanSino Biologics Research Center, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ying","family":"Yang","sequence":"additional","affiliation":[{"name":"CanSino Biologics Research Center, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jinming","family":"Zhang","sequence":"additional","affiliation":[{"name":"CanSino Biologics Research Center, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Liang","family":"Kong","sequence":"additional","affiliation":[{"name":"CanSino Biologics Research Center, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4197-0065","authenticated-orcid":false,"given":"Tao","family":"Zhu","sequence":"additional","affiliation":[{"name":"CanSino Biologics Research Center, Tianjin 300457, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bin","family":"Wang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Drug Regulatory Science, NHC Key Laboratory of Research on Quality and Standardization of Biotech Products, National Institutes for Food and Drug Control, Beijing 102629, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"383","DOI":"10.1080\/21645515.2015.1087625","article-title":"Rationale and prospects for novel pneumococcal vaccines","volume":"12","author":"Moffitt","year":"2016","journal-title":"Hum. Vaccines Immunother."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1186\/s41479-024-00151-x","article-title":"Pneumococci remain the main cause of complicated pediatric pneumonia in the post-pandemic era despite extensive pneumococcal vaccine use","volume":"16","author":"Pinho","year":"2024","journal-title":"Pneumonia"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"194","DOI":"10.1080\/21645515.2015.1052198","article-title":"Next generation protein based Streptococcus pneumoniae vaccines","volume":"12","author":"Pichichero","year":"2016","journal-title":"Hum. Vaccines Immunother."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1128\/MMBR.65.2.187-207.2001","article-title":"Pneumococcal virulence factors: Structure and function","volume":"65","author":"Jedrzejas","year":"2001","journal-title":"Microbiol. Mol. Biol. Rev."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"e00937-20","DOI":"10.1128\/mBio.00937-20","article-title":"A New Pneumococcal Capsule Type, 10D, is the 100th Serotype and Has a Large cps Fragment from an Oral Streptococcus","volume":"11","author":"Ganaie","year":"2020","journal-title":"mBio"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"e0054021","DOI":"10.1128\/JCM.00540-21","article-title":"Structural, Genetic, and Serological Elucidation of Streptococcus pneumoniae Serogroup 24 Serotypes: Discovery of a New Serotype, 24C, with a Variable Capsule Structure","volume":"59","author":"Ganaie","year":"2021","journal-title":"J. Clin. Microbiol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"7479","DOI":"10.1016\/j.vaccine.2020.09.068","article-title":"Seroepidemiological analysis of anti-pneumococcal surface protein A (PspA) immunoglobulin G by clades in Japanese population","volume":"38","author":"Morino","year":"2020","journal-title":"Vaccine"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1962","DOI":"10.1016\/S0140-6736(10)62225-8","article-title":"Serotype replacement in disease after pneumococcal vaccination","volume":"378","author":"Weinberger","year":"2011","journal-title":"Lancet"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"80","DOI":"10.1016\/j.epidem.2010.03.005","article-title":"Evidence that pneumococcal serotype replacement in Massachusetts following conjugate vaccination is now complete","volume":"2","author":"Hanage","year":"2010","journal-title":"Epidemics"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1016\/j.imbio.2009.12.004","article-title":"The immunising effect of pneumococcal nasopharyngeal colonisation; protection against future colonisation and fatal invasive disease","volume":"215","author":"Richards","year":"2010","journal-title":"Immunobiology"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Flasche, S., Van Hoek, A.J., Sheasby, E., Waight, P., Andrews, N., Sheppard, C., George, R., and Miller, E. (2011). Effect of pneumococcal conjugate vaccination on serotype-specific carriage and invasive disease in England: A cross-sectional study. PLoS Med., 8.","DOI":"10.1371\/journal.pmed.1001017"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"354","DOI":"10.25259\/ijmr_1811_23","article-title":"Pre- & post-vaccine trends in pneumococcal serotypes & antimicrobial resistance patterns","volume":"160","author":"Peela","year":"2024","journal-title":"Indian J. Med. Res."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1111\/j.1469-0691.2012.03943.x","article-title":"A century of pneumococcal vaccination research in humans","volume":"18","author":"Grabenstein","year":"2012","journal-title":"Clin. Microbiol. Infect."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1901","DOI":"10.1111\/jam.14079","article-title":"Construction and evaluation of a whole-cell pneumococcal vaccine candidate","volume":"125","author":"Mohammadzadeh","year":"2018","journal-title":"J. Appl. Microbiol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1116","DOI":"10.1093\/infdis\/jit502","article-title":"Broadly protective protein-based pneumococcal vaccine composed of pneumolysin toxoid-CbpA peptide recombinant fusion protein","volume":"209","author":"Mann","year":"2014","journal-title":"J. Infect. Dis."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Masomian, M., Ahmad, Z., Gew, L.T., and Poh, C.L. (2020). Development of Next Generation Streptococcus pneumoniae Vaccines Conferring Broad Protection. Vaccines, 8.","DOI":"10.3390\/vaccines8010132"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Li, S., Liang, H., Zhao, S.H., Yang, X.Y., and Guo, Z. (2023). Recent progress in pneumococcal protein vaccines. Front. Immunol., 14.","DOI":"10.3389\/fimmu.2023.1278346"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"3025","DOI":"10.1016\/j.vaccine.2014.03.066","article-title":"Safety and immunogenicity of an investigational vaccine containing two common pneumococcal proteins in toddlers: A phase II randomized clinical trial","volume":"32","author":"Prymula","year":"2014","journal-title":"Vaccine"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4610","DOI":"10.1016\/j.vaccine.2015.06.078","article-title":"Safety and immunogenicity of a trivalent recombinant PcpA, PhtD, and PlyD1 pneumococcal protein vaccine in adults, toddlers, and infants: A phase I randomized controlled study","volume":"33","author":"Brooks","year":"2015","journal-title":"Vaccine"},{"key":"ref_20","first-page":"927","article-title":"Typing of the PspA protein among Streptococcus pneumoniae strains isolated from children in Nanjing Children\u2019s Hospital","volume":"33","author":"Zhong","year":"2013","journal-title":"Chin. J. Microbiol. Immunol."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Lane, J.R., Tata, M., Briles, D.E., and Orihuela, C.J. (2022). A Jack of All Trades: The Role of Pneumococcal Surface Protein A in the Pathogenesis of Streptococcus pneumoniae. Front. Cell. Infect. Microbiol., 12.","DOI":"10.3389\/fcimb.2022.826264"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"6834","DOI":"10.1016\/j.vaccine.2018.08.045","article-title":"The diversity of the proline-rich domain of pneumococcal surface protein A (PspA): Potential relevance to a broad-spectrum vaccine","volume":"36","author":"Mukerji","year":"2018","journal-title":"Vaccine"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Kono, M., Hotomi, M., Hollingshead, S.K., Briles, D.E., and Yamanaka, N. (2011). Maternal immunization with pneumococcal surface protein A protects against pneumococcal infections among derived offspring. PLoS ONE, 6.","DOI":"10.1371\/journal.pone.0027102"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"2163","DOI":"10.1128\/IAI.01199-09","article-title":"The proline-rich region of pneumococcal surface proteins A and C contains surface-accessible epitopes common to all pneumococci and elicits antibody-mediated protection against sepsis","volume":"78","author":"Daniels","year":"2010","journal-title":"Infect. Immun."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1033","DOI":"10.1128\/IAI.71.3.1033-1041.2003","article-title":"Regions of PspA\/EF3296 best able to elicit protection against Streptococcus pneumoniae in a murine infection model","volume":"71","author":"Roche","year":"2003","journal-title":"Infect. Immun."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"339","DOI":"10.1086\/376571","article-title":"Immunizations with pneumococcal surface protein A and pneumolysin are protective against pneumonia in a murine model of pulmonary infection with Streptococcus pneumoniae","volume":"188","author":"Briles","year":"2003","journal-title":"J. Infect. Dis."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"5889","DOI":"10.1128\/IAI.68.10.5889-5900.2000","article-title":"Diversity of PspA: Mosaic genes and evidence for past recombination in Streptococcus pneumoniae","volume":"68","author":"Hollingshead","year":"2000","journal-title":"Infect. Immun."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1555","DOI":"10.1128\/CVI.00177-08","article-title":"Distribution of pneumococcal surface protein A families 1 and 2 among Streptococcus pneumoniae isolates from children in finland who had acute otitis media or were nasopharyngeal carriers","volume":"15","author":"Melin","year":"2008","journal-title":"Clin. Vaccine Immunol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1099\/jmm.0.46268-0","article-title":"Pneumococcal surface protein A (PspA) family distribution among clinical isolates from adults over 50 years of age collected in seven countries","volume":"55","author":"Hollingshead","year":"2006","journal-title":"J. Med. Microbiol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"4603","DOI":"10.1016\/j.vaccine.2017.07.008","article-title":"Safety, reactogenicity and immunogenicity of two investigational pneumococcal protein-based vaccines: Results from a randomized phase II study in infants","volume":"35","author":"Prymula","year":"2017","journal-title":"Vaccine"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"612","DOI":"10.1177\/1747493018778713","article-title":"Multisociety Consensus Quality Improvement Revised Consensus Statement for Endovascular Therapy of Acute Ischemic Stroke","volume":"13","author":"Sacks","year":"2018","journal-title":"Int. J. Stroke"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"2161","DOI":"10.1128\/CVI.05313-11","article-title":"Prediction of pneumococcal conjugate vaccine effectiveness against invasive pneumococcal disease using opsonophagocytic activity and antibody concentrations determined by enzyme-linked immunosorbent assay with 22F adsorption","volume":"18","author":"Schuerman","year":"2011","journal-title":"Clin. Vaccine Immunol."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"2518","DOI":"10.1016\/j.vaccine.2006.09.029","article-title":"Validation of a routine opsonophagocytosis assay to predict invasive pneumococcal disease efficacy of conjugate vaccine in children","volume":"25","author":"Henckaerts","year":"2007","journal-title":"Vaccine"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"2947","DOI":"10.1016\/j.vaccine.2011.02.002","article-title":"Phase 3 trial evaluating the immunogenicity, safety, and tolerability of manufacturing scale 13-valent pneumococcal conjugate vaccine","volume":"29","author":"Gadzinowski","year":"2011","journal-title":"Vaccine"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"944","DOI":"10.1097\/INF.0000000000003277","article-title":"Safety and Immunogenicity of a 20-valent Pneumococcal Conjugate Vaccine in Healthy Infants in the United States","volume":"40","author":"Senders","year":"2021","journal-title":"Pediatr. Infect. Dis. J."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Xie, Z., Li, J., Wang, X., Huang, L., Gou, J., Zhang, W., Huang, H., You, W., Wang, F., and Li, X. (2024). The Safety and Immunogenicity of a 13-Valent Pneumococcal Polysaccharide Conjugate Vaccine (CRM197\/TT) in Infants: A Double-Blind, Randomized, Phase III Trial. Vaccines, 12.","DOI":"10.3390\/vaccines12121417"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1004","DOI":"10.1128\/CVI.00112-06","article-title":"Development and validation of a fourfold multiplexed opsonization assay (MOPA4) for pneumococcal antibodies","volume":"13","author":"Burton","year":"2006","journal-title":"Clin. Vaccine Immunol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"122","DOI":"10.1038\/s41541-023-00715-w","article-title":"Emerging vaccine strategies against the incessant pneumococcal disease","volume":"8","author":"Duke","year":"2023","journal-title":"npj Vaccines"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"116870","DOI":"10.1016\/j.diagmicrobio.2025.116870","article-title":"Pneumococcal surface proteins as targets for next-generation vaccines: Addressing the challenges of serotype variation","volume":"113","author":"Gopalakrishnan","year":"2025","journal-title":"Diagn. Microbiol. Infect. Dis."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"ofae220","DOI":"10.1093\/ofid\/ofae220","article-title":"Immunogenicity of Current and Next-Generation Pneumococcal Conjugate Vaccines in Children: Current Challenges and Upcoming Opportunities","volume":"11","author":"Feemster","year":"2024","journal-title":"Open Forum Infect. Dis."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"412","DOI":"10.1007\/s10156-013-0601-1","article-title":"Pneumococcal vaccine and opsonic pneumococcal antibody","volume":"19","author":"Song","year":"2013","journal-title":"J. Infect. Chemother."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"e493","DOI":"10.1542\/peds.2009-3027","article-title":"Immunogenicity and safety of 13-valent pneumococcal conjugate vaccine in infants and toddlers","volume":"126","author":"Yeh","year":"2010","journal-title":"Pediatrics"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"540","DOI":"10.1080\/21645515.2018.1532250","article-title":"Safety and immunogenicity of 15-valent pneumococcal conjugate vaccine compared to 13-valent pneumococcal conjugate vaccine in adults \u226565 years of age previously vaccinated with 23-valent pneumococcal polysaccharide vaccine","volume":"15","author":"Peterson","year":"2019","journal-title":"Hum. Vaccines Immunother."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"390","DOI":"10.1093\/cid\/ciab990","article-title":"Pivotal Phase 3 Randomized Clinical Trial of the Safety, Tolerability, and Immunogenicity of 20-Valent Pneumococcal Conjugate Vaccine in Adults Aged \u226518 Years","volume":"75","author":"Essink","year":"2022","journal-title":"Clin. Infect. Dis."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"1549","DOI":"10.1128\/CVI.00371-13","article-title":"Modified opsonization, phagocytosis, and killing assays to measure potentially protective antibodies against pneumococcal surface protein A","volume":"20","author":"Daniels","year":"2013","journal-title":"Clin. Vaccine Immunol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"e0055324","DOI":"10.1128\/mra.00553-24","article-title":"Genome sequences of 36 Streptococcus pneumoniae strains optimized for the multiplexed opsonophagocytosis killing assay","volume":"13","author":"Graffice","year":"2024","journal-title":"Microbiol. Resour. Announc."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"2545032","DOI":"10.1080\/21645515.2025.2545032","article-title":"Approaches to assess new pneumococcal vaccines for immunogenicity, development and licensure","volume":"21","author":"Ganaie","year":"2025","journal-title":"Hum. Vaccines Immunother."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"835","DOI":"10.1128\/CVI.00086-12","article-title":"Development of a fourfold multiplexed opsonophagocytosis assay for pneumococcal antibodies against additional serotypes and discovery of serological subtypes in Streptococcus pneumoniae serotype 20","volume":"19","author":"Burton","year":"2012","journal-title":"Clin. Vaccine Immunol."}],"container-title":["Vaccines"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-393X\/14\/2\/127\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,28]],"date-time":"2026-01-28T15:25:06Z","timestamp":1769613906000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-393X\/14\/2\/127"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,27]]},"references-count":48,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,2]]}},"alternative-id":["vaccines14020127"],"URL":"https:\/\/doi.org\/10.3390\/vaccines14020127","relation":{},"ISSN":["2076-393X"],"issn-type":[{"value":"2076-393X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,27]]}}}