According to the findings of a double-blind, placebo-controlled, randomized phase III clinical trial, recombinant interferon-armed fusion protein vaccine (V-01) worked effectively and safely as a heterologous booster for the SARS-CoV-2 omicron variant and resulted in a robust humoral immune response in inactivated vaccine-primed participants. This study aimed to test effectiveness, immunogenicity, and safety of heterologous boosting using one dose of V-01 vaccine performed between 3-6 months following main immunization.

Healthy adults over the age of 18 or adults who had stable chronic medical problems in the past three months, and who had undergone two doses of an inactivated vaccination main regimen (either CoronaVac or BBIBP-CorV) 3-6 months before were eligible to participate. A total of 10,218 people were randomly allocated to receive either one dose of V-01 vaccine or a placebo. Overall, 419 people were tested for virus-neutralizing antibodies. Protection against confirmed symptomatic coronavirus infection was the major endpoint ascertained.

At 14 days following the booster, neutralizing titers in the V-01 group increased dramatically (11.3-fold; 128.3 to 1452.8). As per the intention-to-treat principle, vaccination effectiveness was 47.8% (95% CI: 22.6 to 64.7) after two months of monitoring. The most common adverse effects were fever, mild-to-moderate pain at the injection site, headache, and exhaustion.

Severe adverse events occurred virtually equally in the V-01 (0.12%) and placebo (0.16%) groups. During the omicron variant pandemic, the V-01 vaccine, which used a unique prototype-sequenced RBD dimer-INF-Pan Fc fusion protein molecular design, was safe, effective, and could elicit substantial immune protection when boosted in inactivated vaccine-primed volunteers.