Covid-19: Omicron subvariant BA.2 is gaining ground. Should we worry?

Two years into the pandemic, a mutated version of the omicron variant, known as BA.2, has become the latest challenge to taming Covid-19.

The subvariant, detected in at least 57 countries, appears to spread even more easily than the original. But so far it doesn’t seem to cause more severe disease and booster shots remain an effective shield. Scientists are racing to answer a number of questions about this variant as they prepare for the next one.

How transmissible is BA.2?
 

Omicron is more transmissible than delta, the variant that became globally dominant in the middle of last year, and