Protection from hospitalization for Omicron variants can drop to 57% from 81% after 6 months from second dose, and can be pushed back up to 90% using booster shots for Pfizer and Moderna vaccines, according to a large CDC study in the US. For Delta variant period last year the vaccine effectiveness against hospitalization was 90% from about two weeks after dose two till 6 months, dropping to 81% after 6 months, and up to 94% after a booster shot. For Omicron variant the currently vaccine effectiveness for same periods is 81%, 57%, and 90%.
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