Omicron variant much slower at infiltrating lung tissue:

We already know that the Omicron variant harbours mutations that make it more transmissible. A team of researchers at Hong Kong University’s faculty of medicine found Omicron replicates 70 times faster than Delta in human airways. The study, which is yet to be peer-reviewed, showed that when compared with both Delta and the original coronavirus, the Omicron variant was much quicker at getting into the bronchus or tubes that run through the upper airways and lungs but much slower at infiltrating the lung tissue itself. According to the researchers, the Omicron variant replicated less efficiently, more than 10 times lower, once inside the human lung tissue than the original SARS-CoV-2 virus, which may suggest lower severity of disease.