It's actually the gold standard. When we recognize the immunity we get from infection, that's what vaccines are trying to mimic. That's why our biggest successes around eradication have been from live attenuated vaccines, such as the smallpox vaccine, because they most closely mimic that infection.
We know that for COVID, it's been unequivocal that people who have had COVID and recovered are better protected from infection obviously, from serious disease and hospitalization, with the caveat that they survive the first infection. Given COVID particularly, we know the risk factors associated with serious outcomes. There are a vast number of people who have already had COVID-19. I think that with omicron, we'll probably be in a better place as more people get that natural immunity.