There are reports that infections with the new Omicron strains of Covid-19 are more severe in previously vaccinated individuals. Is that true, and due to impaired Type I interferon?

Many of the data showing this potential are valid, so again this is a question of degree and not usually of life and death significance, although it can be. There have been individuals who might otherwise have survived their infection, but due to prior vaccination were more vulnerable to the initial onslaught of the virus and succumbed. So nothing is perfect and we made this clear at the outset, that developing a safe and effective vaccine for this coronavirus would likely be problematic because that is a characteristic of these types of viruses, and that is why a novel approach was chosen at the outset with the mRNA technology rather than a traditional vaccine using an attenuated or killed virus. The latter approaches have largely not worked for many viruses of this type and have other risk factors in the bargain. There is still more to learn about the intricacies of what the virus is doing in the body, the differences among the various strains, and the consequences of vaccination and alterations of the body, with respect to level of immunity and severity of illness, should a person become infected and develop a clinical illness.