COVID-19: ECDC reclassifies omicron sub-lineages BA4 and BA5 to variants of concern

ABSTRACT

On 12 May 2022, the ECDC reclassified Omicron sub-lineages BA.4 and BA.5 from variant of interest to variants of concern. Since their discovery in January and February 2022, respectively, BA.4 and BA.5 have dominated South Africa. In Portugal, BA.5 variant proportions have been rising, along with COVID-19 cases and test positive. As of 8 May 2022, the Portuguese National Institute of Health estimated that 37% of positive cases were BA.5. BA.5's daily growth advantage over BA.2 is 13%, equal to South Africa's 12%. With that growth, BA.5 dominated Portugal by 22 May 2022. Symptomatic BA.4 or BA.5 illness is unlikely to protect uninfected people. Vaccinated sera performed better in invitro experiments, however existing vaccinations lose protection against the Omicron version over time. BA.4 and BA.5 are not worse than prior Omicron lineages. This suggests that in the coming weeks and months, these mutations may increase COVID-19 cases in the EU and EEA. BA.4 and BA.5 are now rare in the EU and EEA, but their rapid growth rates predict they will dominate in the following months. The limited data suggests no substantial increase in infection severity compared to the circulating lineages BA.1 and BA.2. As in earlier waves, COVID-19 cases may increase hospital and ICU admissions. Sensitive, representative testing, genomic surveillance, and rapid sequence reporting are essential for early variant detection. Representative testing policies are needed to accurately quantify the proportion of these variants to ongoing viral circulation and the amount to which they may contribute to population-wide adverse outcomes like hospital or ICU admissions. In cases of persistent high or growing viral circulation, the ECDC observed that rapid delivery of a second mRNA COVID-19 booster dose in those 80 years and older was optimum.