{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,22]],"date-time":"2026-04-22T10:40:27Z","timestamp":1776854427936,"version":"3.51.2"},"reference-count":22,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T00:00:00Z","timestamp":1775779200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Company for Vaccine and Biological Production No.1 (VABIOTECH), Ministry of Health"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background: Pneumococcal conjugate vaccines (PCVs) prevent severe disease in children, but high costs limit access. PCV10-SII (PNEUMOSIL), a 10-valent PCV prequalified by the World Health Organization (WHO) in 2019, offers a cost-effective alternative. This study assessed its safety and immunogenicity in Vietnamese children aged 6 weeks\u201324 months. Methods: An open-label, single-arm study enrolled 304 children in three age groups: 6 weeks\u20136 months (n = 151), &gt;6\u201312 months (n = 76), and &gt;12\u201324 months (n = 77). Participants received two or three doses. Safety was evaluated through immediate reactions, adverse events (AEs), serious adverse events (SAEs), and withdrawals. Immunogenicity was measured 28 days after the final dose using serotype-specific IgG geometric mean concentrations (GMCs), opsonophagocytic activity (OPA) titers, and seroresponse rates. The trial was approved by the IRB of the National Ethics Council (code: No. 75\/CN-H\u0110\u0110\u0110 on date 4 June 2021) and was registered with ClinicalTrials.gov, NCT05140720. Results: Of 304 enrolled participants, 294 (96.7%) completed follow-up. No immediate adverse events or serious adverse events occurred. Unsolicited adverse events were reported in 17%, mainly respiratory, while serious adverse events occurred in 4%. Mild local\/systemic reactions (e.g., injection site pain, crying) resolved without sequelae. Immunogenicity was strong, with GMCs 1.8\u20139.11 \u00b5g\/mL, GMTs 277.8\u201322,342, and seroresponse rates &gt;90% for 9 of 10 serotypes, serotype 6B demonstrated a slightly lower seroresponse rate of 88.6%. Conclusions: PCV10-SII demonstrated favorable safety and robust immunogenicity, supporting its inclusion in national immunization programs as an affordable option for pneumococcal disease prevention.<\/jats:p>","DOI":"10.3390\/vaccines14040336","type":"journal-article","created":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T07:55:12Z","timestamp":1775807712000},"page":"336","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Safety and Immunogenicity of SII\u2019s 10-Valent Pneumococcal Conjugate Vaccine (PCV10-SII) in Vietnamese Children Aged from 6 Weeks to 24 Months: An Open-Label, Single-Arm Bridging Study"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-0664-8265","authenticated-orcid":false,"given":"Vu Tung","family":"Son","sequence":"first","affiliation":[{"name":"Department of Military Epidemiology, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6644-7097","authenticated-orcid":false,"given":"Bui Dang The","family":"Anh","sequence":"additional","affiliation":[{"name":"Department of Military Epidemiology, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3777-4080","authenticated-orcid":false,"given":"Vu Ngoc","family":"Hoan","sequence":"additional","affiliation":[{"name":"Department of Military Epidemiology, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1026-3915","authenticated-orcid":false,"given":"Hoang Van","family":"Than","sequence":"additional","affiliation":[{"name":"Department of Military Epidemiology, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bui Kim","family":"Linh","sequence":"additional","affiliation":[{"name":"Department of Military Epidemiology, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"La Thi Huong","family":"Giang","sequence":"additional","affiliation":[{"name":"Department of Military Epidemiology, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-4249-3841","authenticated-orcid":false,"given":"Nguyen Tien","family":"Manh","sequence":"additional","affiliation":[{"name":"Department of Military Epidemiology, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-0790-1645","authenticated-orcid":false,"given":"Luong Thi Thu","family":"Thao","sequence":"additional","affiliation":[{"name":"Department of Military Epidemiology, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hoang Xuan","family":"Cuong","sequence":"additional","affiliation":[{"name":"Southern Branch, Vietnam Military Medical University (VMMU), Ho Chi Minh City 700000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dao Truong","family":"Giang","sequence":"additional","affiliation":[{"name":"Gastroenterology and Hepatology Department, 103 Military Hospital, Vietnam Military Medical University (VMMU), Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Do Tuan","family":"Dat","sequence":"additional","affiliation":[{"name":"Company for Vaccine and Biological Production No.1 (VABIOTECH), Ministry of Health, Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-7325-9571","authenticated-orcid":false,"given":"Le Thi Huong","family":"Giang","sequence":"additional","affiliation":[{"name":"Company for Vaccine and Biological Production No.1 (VABIOTECH), Ministry of Health, Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sandeep C.","family":"Mulay","sequence":"additional","affiliation":[{"name":"Serum Institute of India Pvt. Ltd., 212\/2, Off Soli Poonawalla Road Hadapsar, Pune 411028, India"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vistasp","family":"Sethna","sequence":"additional","affiliation":[{"name":"Serum Institute of India Pvt. Ltd., 212\/2, Off Soli Poonawalla Road Hadapsar, Pune 411028, India"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-7377-3109","authenticated-orcid":false,"given":"Pham Van","family":"Hung","sequence":"additional","affiliation":[{"name":"Company for Vaccine and Biological Production No.1 (VABIOTECH), Ministry of Health, Hanoi 100000, Vietnam"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,4,10]]},"reference":[{"key":"ref_1","unstructured":"Centers for Disease Control and Prevention (2021). 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