The mRNA vaccine was less effective against the South Africa variant compared to the original strain: but mice were still ‘fully protected’, says CureVac as it released the study today. This is similar to data obtained for other vaccines (such as Pfizer, Moderna, J&J and Novavax).
“Emergence of new SARS-CoV-2 strains, which exhibit the potential to escape an existing SARS-CoV-2 immunity, pose an increasing risk to the progress of current global immunization efforts,” said Igor Splawski, Ph.D., Chief Scientific Officer of CureVac. “To our knowledge, this is the first challenge study in a human ACE2 transgenic mouse model of severe disease that shows complete protection against one of the most threatening virus variants.”
In the study - which has yet to be peer reviewed - transgenic mice expressing the human ACE2 receptor (the receptor through which SARS-CoV-2 enters human cells) were immunized with 8μg of CVnCoV at day 0 and again at day 28.
Vaccination resulted in 'robust antibody responses and complete protection (100% survival)' against the original SARS-CoV-2 strain and also B.1.351 (South Africa) challenge infections. CVnCoV vaccination efficiently blocked viral replication of B.1.351 in the lower respiratory tract and brain, and reduced viral replication in the upper respiratory tract in vaccinated and challenged animals.
The full manuscript of the preclinical data is available on the bioRxiv preprint server.
CureVac announced this week that it is also expanding its late-stage clinical trials (Phase 2b/3 trials in Europe and Latin America) to pinpoint efficacy against the UK, South Africa and Brazil virus strains.
The company plans to apply for conditional marketing authorisation in the EU in Q2, 2021.