Phase II data shows NVX CoV2373 booster provides improved antibody response for COVID-19.

Complete data from the study will be submitted to a peer review publication and posted to a preprint server.

The results come from an ongoing Phase II study in the U.S. and Australia in which select participants in the 5-microgram dose cohort received a 5-microgram booster dose 189 days after the initial two-dose regimen to examine the functional immune response. Twenty-eight days following boosting, anti-spike IgG increased approximately 4.6-fold compared to the peak response seen after the second dose (Day 217 GMEU = 200,408 (95% CI: 159,796; 251,342)). This boosted value represents a 3.7 to 4.4-fold increase in anti-spike IgG values that were associated with protection in Novavax' PREVENT-19 and U.K. Phase III clinical studies. Similarly, wild-type neutralization responses increased approximately 4.3-fold compared to the peak response seen after Dose 2 (IC50 neutralization titers = 6,231 (95% CI: 4,738; 8,195)). This boosted value represents a 4.6 to 5.5-fold increase over the neutralization response associated with protection in the PREVENT-19 and U.K. Phase III clinical trials.

Older participants (aged 60-84) showed a 5.4-fold increase in antibody responses, while younger participants (aged 18-59) showed a 3.7-fold increase. Very high levels of functional antibodies to the Alpha (B.1.1.7), Beta (B.1.351) and Delta variants were induced by boosting with NVX-CoV2373, with a 6.6-fold higher Delta variant-specific response when compared to the Delta response observed with the primary vaccination series. The administration of the booster dose was generally well-tolerated.