COVID-19 Breakthrough Infection after Inactivated Vaccine Induced Robust Antibody Responses and Cross-Neutralization of SARS-CoV-2 Variants, but Less Immunity against Omicron

• Main Authors: Nungruthai Suntronwong, Ritthideach Yorsaeng, Jiratchaya Puenpa, Chompoonut Auphimai, Thanunrat Thongmee, Preeyaporn Vichaiwattana, Sitthichai Kanokudom, Thaneeya Duangchinda, Warangkana Chantima, Pattarakul Pakchotanon, Suvichada Assawakosri, Pornjarim Nilyanimit, Sirapa Klinfueng, Lakkhana Wongsrisang, Donchida Srimuan, Thaksaporn Thatsanatorn, Natthinee Sudhinaraset, Nasamon Wanlapakorn, Yong Poovorawan
• Other Authors: Siriraj Hospital
• Format: Article
• Published: 2022
• Subjects: Immunology and Microbiology; Medicine; Pharmacology, Toxicology and Pharmaceutics
• Online Access: https://repository.li.mahidol.ac.th/handle/123456789/74145
• Institution: Mahidol University

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants and the waning of immunity in vaccinated individuals is resulting in increased numbers of SARS-CoV-2 breakthrough infections. This study investigated binding antibody responses and neutralizing activities against SARS-CoV-2 variants, in patients with COVID-19 who had been fully vaccinated with CoronaVac (n = 77), individuals who had been fully vaccinated with CoronaVac but had not contracted COVID-19 (n = 170), and individuals who had received AZD1222 as a third vaccination (n = 210). Breakthrough infection was generally detected approximately 88 days after the second CoronaVac vaccination (interquartile range 68–100 days). Blood samples were collected at a median of 34 days after infection. Binding antibody levels in sera from patients with breakthrough infection were significantly higher than those in individuals who had received AZD1222 as a third vaccination. However, neutralizing activities against wild-type and variants, including alpha (B.1.1.7), beta (B.1.351), and delta (B.1.617.2), were comparable in patients with breakthrough infections and individuals who received a third vaccination with AZD1222, which exceeds 90%. Omicron (B.1.1.529) was neutralized less effectively by serum from breakthrough infection patients, with a 6.3-fold reduction compared to delta variants. The study suggests that breakthrough infection after two doses of an inactivated vaccine can induce neutralizing antibodies against omicron. Further investigation is needed to assess the long-term persistence of antibodies against the omicron variant.