The Ômicron variant of the new coronavirus has already been detected in 110 countries. In a bulletin released on Thursday (23), the World Health Organization (WHO) reported updated data on the main aspects of the lineage related to transmission, severity and impact on interventions, such as diagnosis, treatment and vaccines.
According to WHO, the current understanding of the variant continues to evolve as more data becomes available. There is consistent evidence that Ômicron has a substantial growth advantage over Delta.
Studies show that Ômicron is spreading significantly faster than the Delta variant in countries with documented community transmission, with a doubling period of 2-3 days.
According to WHO, growth rate estimates in South Africa are declining, driven in large part by rates of decline in Gauteng province. The strain was first reported to WHO by South Africa on 24 November.
Variant severity
Data on the clinical severity of patients infected with Ômicron are growing but are still limited, according to the WHO.
Early data from South Africa, the UK and Denmark suggest a reduced risk of hospitalization for Ômicron compared to Delta. However, the risk of hospitalization is only one aspect of severity, which can be changed.
WHO emphasizes that more data from different countries is needed to understand how clinical markers of severity – such as oxygen use, mechanical ventilation and deaths – are associated with Ômicron.
It is currently unclear to what extent the observed reduction in hospitalization risk can be attributed to immunity conferred by previous infections or by vaccination and to what extent Ômicron may be less virulent.
Immunity
Preliminary data from several preprint studies, not yet peer-reviewed, suggest that there is a reduction in neutralizing antibody titers against Ômicron in individuals who have completed the primary vaccination course or who have had previous SARS-CoV-2 infection.
WHO warns that the increased risk of reinfection reported in England, as well as an increasing trend of reinfection cases in Denmark and Israel, can be attributed to a potential immunological escape of Ômicron.
Impact for vaccines
To date, limited data are available on the impact of the Ômicron variant on vaccine efficacy. Preliminary results from vaccine effectiveness studies have been released in South Africa and the United Kingdom.
Data from the UK indicate a significant reduction in symptomatic disease vaccine efficacy for Ômicron compared to Delta after two doses of Pfizer or AstraZeneca vaccine. There was, however, greater effectiveness two weeks after a Pfizer booster, which was slightly less than or comparable to Delta.
A preprint-format study by South African researchers, using data from private health insurance, reported reductions in the effectiveness of Pfizer’s vaccine against infection and, to a lesser degree, against hospitalization.
“The available preliminary data should be interpreted with caution because the studies may be subject to selection bias and the results are based on relatively small numbers,” says the WHO statement.
Diagnosis and treatment
Accurate molecular biology diagnostic technique (RT PCR) and antigen-based rapid diagnostic test assays are capable of detecting the Ômicron variant.
According to the WHO, therapeutic interventions for the care of patients with severe or critical Covid-19 associated with Ômicron, such as corticosteroids and inflammation blockers, are expected to remain effective.
Preliminary data suggest that some of the monoclonal antibodies developed against SARS-CoV-2 may have decreased neutralization against Ômicron. According to the WHO, monoclonal antibodies will need to be tested individually for their binding to the antigen and virus neutralization, and these studies should be prioritized.
Reference: CNN Brasil
