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

Overview

Journal Vaccines (Basel)

Date 2024 Feb 24

PMID 38400124

Authors

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

Soon will be listed here.

Abstract

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 (MNT) and focus reduction (FRNT) 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) ( < 0.05 for all). Seroconversion (titers ≥ 4-fold compared with pre-immune status) persisted 16 weeks (MNT: 6-fold; FRNT: 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.

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