Safety and immunogenicity of a recombinant tandem-repeat dimeric RBD-based protein subunit vaccine (ZF2001) against COVID-19 in adults: two randomised, double-blind, placebo-controlled, phase 1 and 2 trials
In phase 1 (n=50) and phase 2 (n=900) trials, the protein subunit vaccine ZF2001 appears to be well tolerated and immunogenic, supporting the use of the 25mcg dose in a three-dose schedule in an ongoing phase 3 trial for large-scale evaluation of its safety and efficacy.
Source:
The Lancet Infectious Diseases
SPS commentary:
A commentary notes that the state of the current vaccine landscape continues to raise the bar for vaccine candidates and at present, it is unclear whether the use of a three-dose regimen (prime, boost, boost) in a limited timespan for the ZF2001 protein subunit vaccine will offset the benefits of the less demanding storage conditions that limit RNA vaccines. It highlights that as new SARS-CoV-2 variants emerge, the optimal COVID-19 vaccine should provide broad-spectrum coverage, which might be possible with an engineered spike-protein subunit vaccine comprising a more robust adjuvant. It questions if future studies of ZF2001 fall short of the high efficacy milestones seen with the other vaccines developed so far, will people be satisfied with the reduced efficacy.