New Covid booster for Omicron, but is that necessary?

Covid-19 vaccines this fall are likely to be based on the Omicron variant of the coronavirus rather than the original strain, although some experts suggest they may only offer significant benefits for older and immunocompromised people.

Moderna, Pfizer and Novavax have been testing vaccines based on the first BA.1 Omicron variant that became dominant last winter, driving a massive surge in infections...