Two doses of SCB-2019 vaccine plus CpG and alum provides notable protection against the entire severity spectrum of COVID-19 caused by circulating SAR-CoV-2 viruses, including the predominating delta variant.

This ongoing study showed a vaccine efficacy of 67.2% against any severity of RT-PCR-confirmed COVID-19, and 83.7% efficacy against moderate-to-severe COVID-19 in the per-protocol population of participants without previous exposure to SARS-CoV-2.

Efficacy against admission to hospital was 100% and there were no COVID-19-related deaths in the vaccine group, although the low numbers of such cases in the placebo recipients mean these estimates have very wide CIs.

Furthermore, the study also showed a vaccine efficacy of 66.7% efficacy against any severe COVID-19 and 82.5% against moderate-to-severe COVID-19 in the entire study population independent of baseline serostatus, which represents a real-world scenario.

These estimates are consistent with the predicted efficacy based on comparing the S protein binding antibody concentrations after SCB-2019 with those of four authorised vaccines with known efficacy.

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