New SARS-CoV-2 Omicron subvariant. Is XBB.1.5 associated with an increase in COVID-19 morbidity?

Abstract

As a result of genetic changes and mutations of SARS-CoV-2, new variants emerge that have different properties compared to the original strains of the virus, which is a challenge for public health. XBB.1.5, also known as Kraken, is a subvariant of Omicron, and it is the most infectious and transmissible strain of SARS-CoV-2 to date. XBB.1.5 is the dominant strain in the United States of America, spreading worldwide, including in Europe and Asia. XBB.1.5 has properties to evade the immune system and reinfect individuals who have had COVID-19 before due to its strong binding to angiotensin-converting enzyme 2, and antibody evasion. Treatment and postexposure prophylaxis using monoclonal antibodies are ineffective against the Kraken variant, which is especially problematic for immunocompromised individuals and those with contraindications for vaccination, for example due to severe anaphylaxis or anaphylactic shock after prior administration of the vaccine, who require additional preventive measures. However, antiviral drugs including remdesivir, molnupiravir, nirmatrelvir, and ensitrelvir are still effective in treating COVID-19 caused by the XBB.5 variant. Currently, vaccine efficacy against XBB.1.5 variant is yet unknown. However, according to early studies, XBB and its sublineages have a greater ability for immune evasion than other variants, and the protection against infection via vaccination is reduced.