Universal COVID-19 booster vaccine (SCB 2019) candidate demonstrates superior neutralization of Omicron BA.5 subvariant compared to inactivated vaccine

The data showed that SCB-2019 (CpG 1018/Alum) elicited superior levels of neutralizing antibodies against the Omicron BA.5 subvariant, the dominant SARS-CoV-2 variant circulating globally today, when administered as a heterologous third dose in participants who previously received two doses of an inactivated vaccine compared to a third dose of the inactivated vaccine.

“Omicron BA.5 is globally dominant today, representing over 90% of circulating strains, and evidence indicates that it has some degree of immune escape,” said Dr. Nicholas Jackson, President of Global Research and Development of Clover. “It is very encouraging to observe the consistently robust immune response against BA.5 elicited by SCB-2019 across populations, building foundational evidence for SCB-2019’s potentially critical role in addressing the continuing burden of COVID-19—including in countries and regions where inactivated vaccines have been widely used to date.”

A booster dose of SCB-2019 (CpG 1018/Alum) in participants who previously received two doses of the inactivated vaccine elicited superior neutralizing immune responses against Omicron BA.5 compared to responses in participants receiving a third dose of the inactivated vaccine. Preliminary analyses in subjects with low pre-booster neutralizing antibody levels (defined as baseline pre-booster neutralizing antibody titers less than 100 using validated live SARS-CoV-2 neutralization assays) showed that SCB-2019 (CpG 1018/Alum) elicited a 6.5-fold increase in antibody titers against Omicron BA.5 relative to pre-booster levels, with geometric mean titers (GMTs) increasing from 37 (pre-booster) to 240 (14 days post-booster). This response was 5-fold higher than the response to the inactivated vaccine booster, which elicited a 1.6-fold increase in antibody titers against Omicron BA.5 (GMTs: 30 [pre-booster], 48 [14 days post-booster]).

The Omicron BA.5 heterologous booster responses are consistent with prior data from this Phase III study (LINK), which showed a similarly superior response against the SARS-CoV-2 prototype, Omicron BA.1 and Omicron BA.2 for SCB-2019 (CpG 1018/Alum), relative to inactivated vaccine. They are also consistent with previously released results demonstrating the strong SCB-2019 (CpG 1018/Alum)-elicited immune responses against Omicron BA.5 in other populations, including those receiving a homologous third dose of SCB-2019 (CpG 1018/Alum) and those who had a history of SARS-CoV-2 infection at baseline (LINK). Together, these results demonstrate a potentially differentiated breadth of neutralization against the globally dominant Omicron BA.5 subvariant by SCB-2019 (CpG 1018/Alum) vaccination.

These results are part of a Phase III, double-blind, randomized and controlled study that is evaluating the safety and immunogenicity of SCB-2019 (CpG 1018/Alum) administered as a booster dose in individuals who received two doses of inactivated vaccine compared to third, homologous booster dose of the inactivated vaccine. Clover is also currently enrolling a subcohort evaluating SCB-2019 (CpG 1018/Alum) as a fourth dose booster in individuals previously receiving three doses of the inactivated vaccine compared to a fourth, homologous booster dose of the inactivated vaccine. The study has enrolled over 1,500 adult and elderly participants in the Philippines to date.

Clover remains focused on completing regulatory submissions to the China National Medical Products Administration, the European Medicines Agency, and the World Health Organization for SCB-2019 (CpG 1018/Alum) in the second half of 2022, while concurrently preparing for its commercialization in China and globally.