COVID-19: Epidemiologie und Mutationen: Ein Update

Mutations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can enhance the spread and the infectiousness and decrease the protective effect of antibodies present after infection, vaccination or antibody treatment. The alpha variant (B.1.1.7), first seen in Kent/United Kingdom, has increased the R‑value and therefore the infectiousness by 75%; however, the effectiveness of the vaccines against SARS-CoV‑2 available in Germany seems to be only slightly impaired by these mutations. In the case of the beta variant (B.1.351), first described in South Africa, the neutralization ability of antibodies towards SARS-CoV‑2 is decreased. The monoclonal antibodies bamlanivimab and etesivimab, which are used therapeutically, are ineffective. The AstraZeneca vaccine offers almost no protection against mild or moderate disease caused by the beta variant. The gamma variant (P.1 or B.1.1.28.1), which was first found in Brazil, is probably 1.7–2.6 times more transmissible than previous virus strains circulating in Brazil. In addition to the infectiousness, the mortality risk of the gamma variant also seems to be increased between 1.2 and 1.9-fold in adults and between 5 and 8-fold in young persons. The delta variant (B.1.617), first described in India, is now dominant in most countries. It is 50% more infectious than the alpha variant, and the protective effect of vaccinations against symptomatic disease can be decreased (Biontech: delta variant 88%, alpha variant 93.7%; AstraZeneca: delta variant 67%, alpha variant 74.5%). Furthermore, the course of the disease with the delta variant is often more severe than with the wild type. Disease courses with the delta variant are less severe in vaccinated than in nonvaccinated persons, and fatal outcomes are substantially rarer. A high vaccination rate is essential in order to approach herd immunity and to bring the pandemic under control. Even where the protective effect towards mild or moderate disease is decreased, as a rule, vaccination still offers excellent protection against life-threatening and fatal disease courses.