Omicron 4 and 5 become variants of concern (Voc) in the EU. On May 12, the European Center for Disease Prevention and Control Ecdc reclassified these two sub-lineages of the Omicron variant of Sars-CoV-2, BA.4 and BA.5, from variants of interest to Voc. This is what the European body communicates in the latest epidemiological update released today, citing Portugal as an example of the scenario that seems to be emerging. BA.4 and BA.5 were first identified in South Africa in January and February 2022 respectively, and have since become the dominant variants in that area. The ECDC shows that both lineages contain specific mutations in the domain that binds the receptor of the Spike protein (Rbd) with respect to Omicron 2 (BA.2). Preliminary studies suggest a significant change in the antigenic properties of BA.4 and BA.5 compared to Omicron 1 and 2, especially compared to Omicron 1. What Portugal shows is that there is a trend towards increasing proportions of the variants for BA.5 in recent weeks, accompanied by an increase in the number of Covid cases and in the test positive rate. The Portuguese National Institute of Health estimated that BA.5 already accounted for approximately 37% of positive cases as of May 8, 2022. The estimated daily growth advantage for BA.5 over BA.2 is 13%, in line with that reported from South Africa. Assuming such a growth rate, highlights the ECDC, BA.5 will become the dominant variant in Portugal by May 22, 2022.
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