Long-Term Immunogenicity and Safety of a Homologous Third Dose Booster Vaccination with TURKOVAC: Phase 2 Clinical Study Findings with 32-Week Post-Booster Follow-Up
Zafer Sezer,
Shaikh Terkis Islam Pavel,
Ahmet Inal,
Hazel Yetiskin,
Busra Kaplan,
Muhammet Ali Uygut,
Ahmet Furkan Aslan,
Adnan Bayram,
Mumtaz Mazicioglu,
Gamze Kalin Unuvar,
Zeynep Ture Yuce,
Gunsu Aydin,
Refika Kamuran Kaya,
Ihsan Ates,
Ates Kara,
Aykut Ozdarendeli
Affiliations
Zafer Sezer
Department of Medical Pharmacology, Faculty of Medicine, Erciyes University, Kayseri 38280, Türkiye
Shaikh Terkis Islam Pavel
Vaccine Research, Development and Application Centre (ERAGEM), Erciyes University, Kayseri 38280, Türkiye
Ahmet Inal
Department of Medical Pharmacology, Faculty of Medicine, Erciyes University, Kayseri 38280, Türkiye
Hazel Yetiskin
Vaccine Research, Development and Application Centre (ERAGEM), Erciyes University, Kayseri 38280, Türkiye
Busra Kaplan
Vaccine Research, Development and Application Centre (ERAGEM), Erciyes University, Kayseri 38280, Türkiye
Muhammet Ali Uygut
Vaccine Research, Development and Application Centre (ERAGEM), Erciyes University, Kayseri 38280, Türkiye
Ahmet Furkan Aslan
Vaccine Research, Development and Application Centre (ERAGEM), Erciyes University, Kayseri 38280, Türkiye
Adnan Bayram
Department of Anesthesiology and Reanimation, Faculty of Medicine, Erciyes University, Kayseri 38280, Türkiye
Mumtaz Mazicioglu
Department of Family Medicine, Faculty of Medicine, Erciyes University, Kayseri 38280, Türkiye
Gamze Kalin Unuvar
Department of Infectious Diseases and Clinical Microbiology, Faculty of Medicine, Erciyes University, Kayseri 38280, Türkiye
Zeynep Ture Yuce
Department of Infectious Diseases and Clinical Microbiology, Faculty of Medicine, Erciyes University, Kayseri 38280, Türkiye
Gunsu Aydin
Vaccine Research, Development and Application Centre (ERAGEM), Erciyes University, Kayseri 38280, Türkiye
Refika Kamuran Kaya
Health Institutes of Türkiye (TUSEB), Istanbul 34718, Türkiye
Ihsan Ates
Department of Internal Medicine, University of Health Sciences Ankara City Hospital, Ankara 06530, Türkiye
Ates Kara
Health Institutes of Türkiye (TUSEB), Istanbul 34718, Türkiye
Aykut Ozdarendeli
Vaccine Research, Development and Application Centre (ERAGEM), Erciyes University, Kayseri 38280, Türkiye
Vaccine-induced immunity wanes over time and warrants booster doses. We investigated the long-term (32 weeks) immunogenicity and safety of a third, homologous, open-label booster dose of TURKOVAC, administered 12 weeks after completion of the primary series in a randomized, controlled, double-blind, phase 2 study. Forty-two participants included in the analysis were evaluated for neutralizing antibodies (NAbs) (with microneutralization (MNT50) and focus reduction (FRNT50) tests), SARS-CoV-2 S1 RBD (Spike S1 Receptor Binding Domain), and whole SARS-CoV-2 (with ELISA) IgGs on the day of booster injection and at weeks 1, 2, 4, 8, 16, 24, and 32 thereafter. Antibody titers increased significantly from week 1 and remained higher than the pre-booster titers until at least week 4 (week 8 for whole SARS-CoV-2) (p 50: 6-fold; FRNT50: 5.4-fold) for NAbs and 32 weeks for S1 RBD (7.9-fold) and whole SARS-CoV-2 (9.4-fold) IgGs. Nine participants (20.9%) tested positive for SARS-CoV-2 RT-PCR between weeks 8 and 32 of booster vaccination; none of them were hospitalized or died. These findings suggest that boosting with TURKOVAC can provide effective protection against COVID-19 for at least 8 weeks and reduce the severity of the disease.