Yes, I'll take that question.
Despite the change in the spike protein through different variants, up until omicron, two doses of vaccine retained really good vaccine effectiveness against the most prominent ones, even though we were monitoring for waning immunity. When omicron arrived, even though it looked significantly different from the delta and preceding variants, through our vaccine effectiveness estimates, a boost provided at least an initial protection of 60%, as a range, against infection and symptomatic disease, and over 90% vaccine effectiveness against severe disease with the third dose. That could wane over time, but that's still good news.