Mawer 2026 and the COV-CHIM01 study team found that, when examining which pre-existing immune responses protect previously vaccinated or infected people from early SARS-CoV-2 replication following controlled exposure, higher nasal IgG antibodies against the spike protein, particularly the RBD, were the strongest CoP against quantifiable viral shedding.
The Mucosal Immunity in Human Coronavirus Challenge (MusiCC) project is conducting a CHIM study to expose vaccinated volunteers to the Omicron BA.5 subvariant of SARS-CoV-2. The goal is to elucidate the immune responses required to protect against breakthrough infection.
- Jackson 2024 found that:
- Only a low percentage (14%) of seropositive subjects exhibited transient infection with detectable viral kinetics when infected with pre-alpha SARS-CoV-2, but exhibited no persistent replication.
- 39% of subjects developed breakthrough community acquired infections with omicron after the study.
- The findings suggest a need for CHIMs using newer SARS-CoV-2 variants to reflect real-world infection dynamics, necessitating the above mentioned study.