{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,7]],"date-time":"2026-08-07T15:16:38Z","timestamp":1786115798726,"version":"build-2736575974"},"reference-count":47,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,8,6]],"date-time":"2026-08-06T00:00:00Z","timestamp":1785974400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>Understanding how different COVID-19 vaccine combinations shape long-term immunity is essential for improving durability and guiding booster strategies. Despite extensive characterization of neutralizing antibodies, long-term memory B and T cell responses after homologous and heterologous vaccination regimens remain poorly understood.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      In this study, peripheral blood mononuclear cells (PBMCs) from 50 individuals were analyzed 12 months after completion of a homologous two-dose primary COVID-19 vaccination series and had received a single booster dose (12-month follow-up). Participants initially received BNT162b2, ChAdOx1 nCoV-19, or CoronaVac as the primary vaccination series, followed by either a homologous booster or a heterologous BNT162b2 booster (ChAdOx1 nCoV-19\/BNT162b2 and CoronaVac\/BNT162b2). Unvaccinated individuals served as controls. B cell phenotypes were assessed using flow cytometry, while B and T cell recall responses were determined using ELISpot. IgG levels and cytokine\/chemokine\/growth factor profiles were evaluated using ELISA and Bio-Plex multiplex before and after\n                      <jats:italic>in vitro<\/jats:italic>\n                      stimulation.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>The homologous BNT162b2 vaccination regimen exhibited significantly higher frequencies of memory B cells recognizing the ancestral (Wuhan strain-derived) SARS-CoV-2 Spike protein compared to the ChAdOx1 nCoV-19, CoronaVac, and unvaccinated controls. The CoronaVac\/BNT162b2 vaccination regimen demonstrated significantly elevated RBD-specific IgG+ memory B cells and higher stimulated IgG levels, together with the highest IFN-\u03b3-producing T cell responses. Homologous CoronaVac and CoronaVac\/BNT162b2 vaccination regimens showed broader cytokine activation, including IL-6, IL-9, IL-15, TNF-\u03b1, and other cytokines. IL-6 levels were positively associated with memory B cell frequencies, suggesting a potential association with memory B cell differentiation and maintenance.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Discussion<\/jats:title>\n                    <jats:p>Different vaccination regimens were associated with distinct long-term cellular immune profiles under real-world conditions, with both homologous BNT162b2 and heterologous CoronaVac\/BNT162b2 vaccination regimens maintaining robust memory B cell signatures and functional recall responses. The results highlight how priming combinations shape the durability and quality of immune memory, supporting the potential utility of mixed-platform booster strategies for sustaining long-term immunity.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fimmu.2026.1921846","type":"journal-article","created":{"date-parts":[[2026,8,6]],"date-time":"2026-08-06T05:33:49Z","timestamp":1785994429000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Differential functional immune recall across homologous and heterologous COVID-19 vaccination regimens"],"prefix":"10.3389","volume":"17","author":[{"given":"Naim","family":"Che-Kamaruddin","sequence":"first","affiliation":[{"name":"Tropical Infectious Diseases Research and Education Centre (TIDREC), Higher Institution Centre of Excellence (HICoE), Universiti Malaya","place":["Kuala Lumpur, Malaysia"]},{"name":"Institute for Advanced Studies, Universiti 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