An effective vaccine is needed to end the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Here, we assess the preliminary safety, tolerability and immunogenicity data from an ongoing single-center (in Jiangsu province, China), parallel-group, double-blind phase 1 trial of the vaccine candidate BNT162b1 in 144 healthy SARS-CoV-2-naive Chinese participants. These participants are randomized 1:1:1 to receive prime and boost vaccinations of 10 µg or 30 µg BNT162b1 or placebo, given 21 d apart, with equal allocation of younger (aged 18-55 years) and older adults (aged 65-85 years) to each treatment group (ChiCTR2000034825). BNT162b1 encodes the SARS-CoV-2 spike glycoprotein receptor-binding domain (RBD) and is one of several messenger RNA-based vaccine candidates under clinical investigation. Local reactions and systemic events were generally dose dependent, transient and mild to moderate. Fever was the only grade 3 adverse event. BNT162b1 induced robust interferon-γ T cell responses to a peptide pool including the RBD in both younger and older Chinese adults, and geometric mean neutralizing titers reached 2.1-fold (for younger participants) and 1.3-fold (for the older participants) that of a panel of COVID-19 convalescent human sera obtained at least 14 d after positive SARS-CoV-2 polymerase chain reaction test. In summary, BNT162b1 has an acceptable safety profile and produces high levels of humoral and T cell responses in an Asian population.

Background We assessed the safety and immunogenicity of a recombinant adenovirus type-5 (Ad5)-vectored COVID-19 vaccine with homologous prime-boost regimens in healthy participants aged 6 years and above. Methods In this randomised, double-blind, placebo-controlled trial, participants received low-dose vaccine, middle-dose vaccine or placebo. Prime-booster regimens were given intramuscularly 56 days apart. ELISA antibodies to the receptor binding domain (RBD) and pseudovirus neutralising antibodies were detected. Adverse events were monitored for 28 days following each vaccination. Results A total of 430 participants were enrolled in the study, with 30 participants aged 18-55 years (MID cohort), 250 participants aged 56 years and older (OLD cohort), and 150 participants aged 6-17 years (MIN cohort). Ad5-vectored COVID-19 vaccine induced significant RBD-specific ELISA antibodies which decreased with increasing age, with geometric mean titres (GMTs) of 1037.5 in MIN cohort, 647.2 in MID cohort, and 338.0 in OLD cohort receiving 5×10 10 viral particles on day 28 following boost vaccination. Pseudovirus neutralising antibodies showed a similar pattern, with GMTs of 168.0 in MIN cohort, 76.8 in MID cohort, and 79.7 in OLD cohort. A single dose in children and adolescents induced higher antibody responses than that elicited by two doses in adults, with GMTs of 1091.6 and 96.6 in ELISA antibody and neutralising antibody, respectively. Homologous prime-boost vaccination was safety and tolerable. Conclusions Ad5-vectored COVID-19 vaccine with a single dose was safe and induced robust immune responses in children and adolescents aged 6-17 years. A prime-boost regimen needs further exploration for Ad5-vectored COVID-19 vaccine.

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