# Longitudinal analysis of neutralizing antibodies against SARS-CoV-1 and different SARS-CoV-2 strains in breakthrough and unvaccinated COVID-19 patients in Thailand (2021-2022) **Authors:** Prapassorn Poolchanuan, Vichapon Tiacharoen, Adul Dulsuk, Rungnapa Phunpang, Chakkaphan Runcharoen, Thitiya Boonprakob, Onura Hemtong, Suchada Chowplijit, Vachara Chuapaknam, Tanaya Siripoon, Watcharapong Piyaphanee, Le Van Tan, Susanna Dunachie, Chee Wah Tan, Lin-Fa Wang, Wasun Chantratita, Viravarn Luvira, Narisara Chantratita, Nguyen To Anh, Nguyen To Anh, Nguyen Thi Thu Hong, Truong Hoang Chau Truc, Nguyen Thi Han Ny, Do Duong Kim Han, Le Kim Thanh, Lam Anh Nguyet, Cao Thu Thuy, Le Nguyen Truc Nhu, Tran Tan Thanh, Nguyen To Anh, Lam Minh Yen, Vu Thi Ty Hang, Pham Tieu Kieu, Vo Tan Hoang, Nguyen Thi Thao, Mary Chambers, Vu Duy Thanh, Tran Chieu Hoang, CLouise Thwaites, Guy Thwaites, H.Rogier van Doorn, Trinh Son Tung, Raph L Hamers, Anuraj Shankar, Juthathip Mongkolsapaya, Gavin Screaton, Aiete Dijokaite-Guraliuc, Raksha Das, Chang Liu, Piyada Supasa, Muneeswaran Selvaraj, Paul Klenerman, EYvonne Jones, David I Stuart, Barbara Kronsteiner-Dobramysl, Martha Zewdie, Priyanka Abraham, Jennifer Hill, Wee Chee Yap, Beng Lee Lim, Suwarti Suwarti, Yanie Tayipto, Eva Simarmata, Ragil Dien, Wanwisa Dejnirattisai, Warangkana Chantima, Apirak Junpirom, Sopon Iamsirithaworn, Nicholas P.J. Day, Phaik Yeong Cheah, Tassawan Poomchaichote, Kanpong Boonthaworn, Nghiem My Ngoc, Alba Grifoni, Alessandro Sette PMC · DOI: 10.1038/s41598-025-33388-7 · 2026-01-03 ## TL;DR This study analyzed how neutralizing antibodies in Thai patients changed over time against different SARS-CoV-2 variants and SARS-CoV-1, showing varied immune responses based on vaccination type, age, and health conditions. ## Contribution The study provides new insights into the dynamics of neutralizing antibodies against multiple SARS-CoV-2 strains and SARS-CoV-1 in vaccinated and unvaccinated individuals in Thailand. ## Key findings - Neutralizing antibody levels increased within two weeks but declined by day 60. - Heterologous vaccination led to higher neutralizing antibody levels in breakthrough cases. - Older breakthrough patients showed faster antibody decline compared to younger individuals. ## Abstract The emergence of SARS-CoV-2 variants that evade immune responses poses challenges to effective prevention. We prospectively enrolled 111 COVID-19 patients in Thailand (2021-2022), who received homologous or heterologous vaccines or were unvaccinated. Plasma neutralizing antibody (nAb) levels against SARS-CoV-1 and 13 SARS-CoV-2 strains were measured using a multiplex surrogate virus neutralization test (sVNT) assay within a year. nAb levels increased in two weeks, showing strong inhibition against ancestral SARS-CoV-2 and non-omicron variants, but not against SAR-CoV-1 and lower responses to omicron variants. nAb levels declined by the day 60. Breakthrough patients with heterologous vaccines had higher nAb levels compared to other groups. nAb levels were lower in breakthrough patients with pneumonia than those with other conditions. Notably, breakthrough patients aged ≥60 showed rapid declines in antibody levels. Our findings highlight diverse immune responses influenced by immunization, age, and clinical conditions, underscoring the need for tailored vaccination strategies against evolving variants. The online version contains supplementary material available at 10.1038/s41598-025-33388-7. ## Linked entities - **Diseases:** COVID-19 (MONDO:0100096), pneumonia (MONDO:0005249) ## Full-text entities - **Diseases:** pneumonia (MESH:D011014), COVID-19 (MESH:D000086382) - **Species:** Severe acute respiratory syndrome coronavirus 2 (no rank) [taxon 2697049], Homo sapiens (human, species) [taxon 9606] ## Figures 6 figures with captions in the complete paper: https://tomesphere.com/paper/PMC12835167/full.md --- Source: https://tomesphere.com/paper/PMC12835167