Covid, Omicron 4 and 5 become variants of concern

Omicron 4 and 5 become Covid 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.

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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 an increasing trend in the proportions of variants for BA.5 in recent weeks, accompanied by an increase in the number of Covid cases and the positive rate on tests. The Portuguese National Institute of Health estimated that BA.5 already accounted for around 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.

The growth advantage currently observed for BA.4 and BA.5 is “likely due to their ability to evade the immune protection induced by a previous infection and / or vaccination, particularly if this” immunity “has decreased over time,” he explains. the Ecdc. The limited data available from in vitro studies on sera from unvaccinated who had a previous Omicron 1 infection indicate that both Omicron 4 and Omicron 5 are able to escape the immune protection induced by BA.1 infection. “These unvaccinated people are unlikely to be protected against symptomatic infection with BA.4 or BA.5.” Vaccinee sera have performed better in in vitro studies conducted to date, but the protection from currently available vaccines declines over time against the Omicron variant, the agency notes.

At present, however, “there is no indication of a change in the severity of Covid for BA.4 / BA.5 compared to previous Omicron lineages”. Overall, the available information indicates that “the presence of these variants could cause a significant overall increase in Covid cases in the EU / See in the coming weeks and months”. For this the ECDC “‘encourages countries to remain vigilant. Early detection of variants is crucially based on sensitive and representative tests and genomic surveillance”.

As for vaccines, “the public health benefit deriving from the second booster dose of the anti-Covid vaccine,” was evaluated as more evident in the over 80s “by the ECDC. If signs of increased circulation of SARS emerge. CoV-2 or the risk of serious disease among vaccinees, then “a second booster may be considered for some or all adults 60 years of age and older and other vulnerable groups.” For this, “the countries they should have plans in place for the rapid deployment of booster doses in these population groups. “For all age groups in general, improving primary and first booster adherence remains a priority in groups that have yet to receive them. is the warning of the ECDC.


The overall share of Omicron 4 and 5 (BA.4 and BA.5) in the European Union / European Economic Area “is currently low, but the reported high growth benefits” for these two sub-lineages “suggest that these variants will become dominant in the ‘area in the coming months “, promises the ECDC.

“Based on the limited data currently available, no significant increase in the severity of the infection is expected compared with circulating strains Omicron 1 and 2 (BA.1 and BA.2). However, as in previous waves, if the number of cases Covid will increase substantially, it is likely to follow a certain level of increase in hospital and intensive care admissions “, specifies the ECDC.

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