{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T15:30:01Z","timestamp":1788881401032,"version":"build-2803163510"},"reference-count":32,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T00:00:00Z","timestamp":1760054400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Vaccines"],"abstract":"<jats:p>Background: In the Kingdom of Saudi Arabia, various COVID-19 vaccines were administered during the pandemic. However, region-specific real-word comparative data on their immunogenicity remain limited. This study aimed to assess the serological responses to Pfizer-BioNTech (BNT162b2), Moderna (mRNA-1273), and AstraZeneca (ChAdOx1 nCoV-19) vaccines in a diverse population living in KSA. Methods: This observational study included 236 adults recruited from vaccination sites in Riyadh. Participants provided serum samples at predefined intervals: before the first dose, after the first dose, after the second dose, and post-vaccination infection (if applicable). IgG and neutralising antibodies were quantified using ELISA assays. Demographic and vaccination data, and their associations with antibody responses, were evaluated. Results: At baseline, 75.4% of participants were positive for SARS-CoV-2 IgG, suggesting high prior exposure. Marked incremental increases in IgG levels were observed after each vaccine dose. Both Moderna and Pfizer elicited stronger responses, with Pfizer inducing the strongest early response and Moderna achieving the highest overall titres. Among IgG-positive individuals, neutralising antibodies were detected in 98.1%. There were no statistically significant differences by age or gender, although males tended to show higher mean titres. Heterologous vaccine schedules induced comparable or enhanced immunogenicity relative to homologous schedules, supporting their use in flexible immunisation strategies. Conclusions: All COVID-19 vaccines administered in Saudi Arabia elicited robust antibody responses, particularly the mRNA-based vaccines. Our findings support their continued use and justify varied vaccination approaches, including mix-and-match booster strategies, to enhance community immunity.<\/jats:p>","DOI":"10.3390\/vaccines13101042","type":"journal-article","created":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T09:45:01Z","timestamp":1760089501000},"page":"1042","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Serological Response to COVID-19 Vaccination in Saudi Arabia: A Comparative Study of IgG and Neutralising Antibodies Across Vaccine Platforms"],"prefix":"10.3390","volume":"13","author":[{"given":"Mariam M.","family":"AlEissa","sequence":"first","affiliation":[{"name":"College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia"},{"name":"Ministry of Health, Riyadh 11176, Saudi Arabia"},{"name":"Public Health Lab, Public Health Authority, Riyadh 11176, Saudi Arabia"},{"name":"King Khaled Eye Specialist Hospital (KKESH) Research Center, Riyadh 11462, Saudi Arabia"},{"name":"Computational Sciences Department, Centre for Genomic Medicine (CGM), King Faisal Specialist Hospital & Research Center, Riyadh 11211, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ahdab A.","family":"Alsaieedi","sequence":"additional","affiliation":[{"name":"Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia"},{"name":"King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21589, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Reema","family":"Alduaiji","sequence":"additional","affiliation":[{"name":"John Hopkins Aramco Healthcare, ARAMCO Saudi Arabia, Dhahran 31311, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3421-1394","authenticated-orcid":false,"given":"Fahad","family":"Almsned","sequence":"additional","affiliation":[{"name":"Research Center, King Fahad Specialist Hospital in Dammam (KFSH-D), Dammam 32253, Saudi Arabia"},{"name":"Research Program, Academic, Training, and Research Administration, Eastern Health Cluster, Dammam 32253, Saudi Arabia"},{"name":"School of Systems Biology, George Mason University, Fairfax, VA 22030, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yousif","family":"AlDossary","sequence":"additional","affiliation":[{"name":"Research Center, King Fahad Specialist Hospital in Dammam (KFSH-D), Dammam 32253, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3744-7378","authenticated-orcid":false,"given":"Nada","family":"Saleh","sequence":"additional","affiliation":[{"name":"College of Medicine, King Saud bin Abdulaziz University for Health Sciences (KSAU-HS), Riyadh 11481, Saudi Arabia"},{"name":"King Abdullah International Medical Research Centre (KAIMRC), Ministry of National Guard Health Affairs (MNGHA), Riyadh 11426, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Raghad A.","family":"AlQurashi","sequence":"additional","affiliation":[{"name":"Public Health Lab, Public Health Authority, Riyadh 11176, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Esraa A.","family":"Hawsa","sequence":"additional","affiliation":[{"name":"Public Health Lab, Public Health Authority, Riyadh 11176, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Muath b","family":"Ben Shaded","sequence":"additional","affiliation":[{"name":"Public Health Lab, Public Health Authority, Riyadh 11176, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amer M.","family":"Alshehri","sequence":"additional","affiliation":[{"name":"Public Health Lab, Public Health Authority, Riyadh 11176, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6641-4044","authenticated-orcid":false,"given":"Osamah T.","family":"Khojah","sequence":"additional","affiliation":[{"name":"Pathology Department, College of Medicine, King Saud University, Riyadh 12372, Saudi Arabia"},{"name":"Medical Diagnostic Laboratories, Sulaiman Alhabib Medical Group, Riyadh 12511, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eyad Y.","family":"Abu Sarhan","sequence":"additional","affiliation":[{"name":"Medical Diagnostic Laboratories, Sulaiman Alhabib Medical Group, Riyadh 12511, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0008-4620-6553","authenticated-orcid":false,"given":"Hamad H.","family":"Alonazi","sequence":"additional","affiliation":[{"name":"Ministry of Health, Riyadh 11176, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Walid A.","family":"Nouh","sequence":"additional","affiliation":[{"name":"Medical Diagnostic Laboratories, Sulaiman Alhabib Medical Group, Riyadh 12511, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Khalid H.","family":"AlAnazi","sequence":"additional","affiliation":[{"name":"Ministry of Health, Riyadh 11176, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6653-9592","authenticated-orcid":false,"given":"Sami S.","family":"Almudrra","sequence":"additional","affiliation":[{"name":"Gulf Center for Disease Prevention and Control, Gulf Health Council, Riyadh 11481, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Khaled 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