Pfizer is confident its COVID-19 antiviral pill, Paxlovid, will be effective against the new omicron variant, the drugmaker’s CEO told CNBC Nov. 29.

The omicron strain, first detected in South Africa, contains 32 mutations in the spike protein, and while preliminary evidence suggests the strain may increase the risk of reinfection, it’s still uncertain how the variant may affect illness severity or the effectiveness of vaccines and treatments.

Albert Bourla, PhD, Pfizer’s CEO, told CNBC the company’s antiviral was created with the spike protein in mind and expects it will work against omicron.