April’s COVID-19 Infections Entirely from Omicron Subvariants
In April, all COVID-19 cases sequenced in Singapore were found to be caused by the Omicron variant, as confirmed by the Ministry of Health (MOH). Of the local infections, 99% were attributed to the BA.2 subvariant and its lineages, including BA.2.12.1. The remaining 1% involved the BA.1 strain and its related variants. Among imported cases, 98% were BA.2 and its lineages, with 1% involving BA.1, as well as recombinant lineages such as the XJ and XE variants.
A total of 101,480 local and imported infections were recorded in April, including two cases of the BA.4 variant. Singapore’s first two community cases of BA.4 were reported earlier in May, along with a local case of BA.5. Both of these Omicron subvariants, first identified in South Africa in early 2022, have since become dominant in the region.
Health Minister Ong Ye Kung commented that the emergence of new Omicron subvariants was expected, as COVID-19 is known to mutate over time. He also highlighted that while BA.4 and BA.5 have a transmission advantage over BA.1 and BA.2, there is no current evidence suggesting that these subvariants cause more severe illness.
Scientists in South Africa have observed that BA.4 and BA.5 can evade antibodies from prior infections but are less capable of thriving in the blood of vaccinated individuals. Despite limited knowledge of these variants, the World Health Organization included them in its monitoring list in April.
