Higher Delta variant-specific neutralizing antibodies prevented infection in close contacts vaccinated with ancestral mRNA vaccines during the SARS-CoV-2 Delta wave

• Main Authors: Goh, Yun Shan, Fong, Siew-Wai, Tay, Matthew Zirui, Rouers, Angeline, Chang, Zi Wei, Chavatte, Jean-Marc, Hor, Pei Xiang, Loh, Chiew Yee, Huang, Yuling, Tan, Yong Jie, Wang, Bei, Ngoh, Eve Zi Xian, Siti Nazihah Mohd Salleh, Lee, Raphael Tze Chuen, Lim, Georgina, Maurer-Stroh, Sebastian, Wang, Cheng-I, Leo, Yee-Sin, Lin, Raymond T. P., Lam, Meng Chon, Lye, David C., Young, Barnaby Edward, Ng, Lisa F. P., Renia, Laurent
• Other Authors: Lee Kong Chian School of Medicine (LKCMedicine)
• Format: Article
• Language: English
• Published: 2024
• Subjects: Medicine, Health and Life Sciences; SARS-CoV-2 Delta; mRNA vaccines
• Online Access: https://hdl.handle.net/10356/173859
• Institution: Nanyang Technological University

Identification of the risk factors and the high-risk groups which are most vulnerable is critical in COVID-19 disease management at a population level. Evaluating the efficacy of vaccination against infections is necessary to determine booster vaccination strategies for better protection in high-risk groups. In this study, we recruited 158 mRNA-vaccinated individuals during the Delta wave of SARS-CoV-2 infections in Singapore and examined the antibody profiles of infected individuals. We found that, despite high exposure due to communal living conditions in proximity, 4% of individuals (6/158) had PCR-confirmed infections and 96% (152/158) remained uninfected. Time-course analysis of the antibody profile at the start and the end of quarantine period showed Delta-specific boosting of anti-spike antibody response in 57% of the uninfected individuals (86/152). In the remaining 43% of the uninfected individuals (66/152) with no Delta-specific antibody boost, we found a higher Delta-specific antibody response at the start of quarantine period, which correlated with higher Delta pseudovirus neutralizing capacity. Our findings indicate that a higher basal variant-specific antibody response in the mRNA-vaccinated individuals contributes to better protection against infections by the new emerging SARS-CoV-2 variants.