According to the findings of a recent phase 3 trial, the receptor-binding domain (RBD)-dimer based COVID-19 vaccine (ZF2001) has a good safety profile and is effective for the management of coronavirus infection.  In this randomized, double-blind, placebo-controlled study, the investigators aimed to assess the effectiveness and safety of ZF2001 in adult subjects (aged ≥18 years).

The volunteers were randomized to get three 25 μg doses (thirty days apart) of ZF2001 vaccine or placebo. Overall, 28,873 subjects were given a minimum of 1 dosage of ZF2001 or placebo and were incorporated in the safety analysis. A total of 25,193 subjects who had accomplished the three-dose regime and for whom there were around six months of follow-up data, were incorporated in the updated primary efficacy evaluation.

The incidence of polymerase-chain-reaction assay- confirmed symptomatic coronavirus infection at least 7 days post administration of the third dose was the primary endpoint ascertained. The incidence of severe-to-critical SARS-CoV-2 infection (along with COVID-19–related mortality) at least 7 days post administration of the third dose was the secondary outcome ascertained.

The major outcomes were noted in 158 out of 12,625 volunteers in the ZF2001 cohort and 580 out of 12,568 volunteers in the placebo cohort in the updated analysis. The vaccine efficacy was found to be 75.7%. Overall, 6 and 43 subjects had severe-to-critical COVID-19 in the ZF2001 group and placebo group respectively. The effectiveness of vaccine was found to be 87.6%.

Coronavirus associated death was reported in 2 subjects in the ZF2001 group and 12 subjects in the placebo group. The vaccine efficacy was reported to be 86.5%. The occurrence of serious adverse events and side effects in both groups was balanced. No vaccine-related fatalities were reported. As found, 98.5% of adverse reactions were of grade 1 or 2.

To conclude, an RBD-based vaccine is a promising alternative to prevent symptomatic COVID-19 infection and would offer crucial immunity to mitigate the burden on health care services.