What would stand out from the positive results announced by Moderna is the bivalent vaccine aspect. In fact, the results in animal models of their omicron-specific vaccines were not as good as desirable (work still in preprint). These results, and others that are becoming known, probably led them to include vaccines for more than one variant in the new formulations. This reflects the complex situation with circulating variants right now, and the need to develop new vaccines designed to be effective against several variants of concern (VOC) which, at this stage, necessarily involves combining antigens in vaccine candidates even if they are developed as booster doses.

On the other hand, the high circulation of omicron and its derived variants leads, at the moment, to a high rate of infections mostly with mild symptoms or asymptomatic due to the efficacy of current vaccines. This also indicates that the current vaccines should be improved if a booster is needed in the future for the most vulnerable population.

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