Long Term Follow Up of Antibody Titres Against SARS-CoV-2 6 Months After Primary Protein Subunit COVID-19 Vaccination

Nearly 3 years after the emergence of COVID-19, it remains one of the world's problems. COVID-19 vaccination is a priority programme for reducing death and severe symptoms. The primary recombinant novel coronavirus ZF2001 vaccine has gone through Phase III clinical trials and demonstrates efficacy against the highly critical COVID-19 globally and in Indonesia (87.6% and 76.0%, respectively). This study aimed to assess immune persistence after three doses of ZF2001. The study monitored and followed up 400 participants 14 days and 6 months after the third dose and investigated immune persistence 6 months after the phase III vaccination (ZF2001). This study was conducted at recruitment locations in Bandung. Participants were divided into the vaccine and placebo groups and entered into the immunogenicity group. The immune persistence of the vaccine was assessed by measuring geometric mean titres (GMT), neutralising antibodies and seropositivity of IgG anti-S-receptor-binding domain (RBD) after 14 days and 6 months. The seropositive antibody rates were nearly the same between 14 days and 6 months. After 6 months, the GMT, seropositivity of IgG anti-S-RBD and neutralising antibodies in the vaccine group decreased significantly, from 6447.63 to 1514.61 with a P-value of 0.001. A booster was considered important after 6 months. Keywords: recombinant novel coronavirus, ZF2001, vaccine, COVID-19