Two Malaysian students who returned from the United Kingdom last month were found to be carriers of a Covid-19 lineage known as AY.4.2 – a subvariant of the Delta variant that is sometimes informally referred to as "Delta Plus".

AY.4.2 is notable for being reportedly 10 to 15 percent more transmissible than the Delta variant, which is already one of the most transmissible variants of the disease.

Health director-general Dr Noor Hisham Abdullah, however, said that vaccines...