Omicron: What do we know so far?

This policy brief comprehensively gathers and compares the results of studies on the SARS-CoV-2 variant ‘Omicron’ to enable a more conscious argumentation for policy measures. For this purpose, studies and reports were collected by regular screenings of medRxiv, scientific databases and websites of national health authorities.
Overall, studies reveal that compared to Delta, the risk of hospitalization is reduced by 50% to 80%, risk of ICU admission by 65% to 85% and risk of fatal course by 65% to 75% but reduced by a lower amount among older adults. VE of two doses against infection is only significant within the first months at 55% to 65% and waning over time while a 3rd dose pushes VE up to 55% to 70% again. On the contrary, VE against hospitalization seems to be more stable at 55% to 80% up to 6 months and might be increased to about 85% with a 3rd dose. Most studies report the number of ICU admissions and deaths after vaccination as too low to estimate VE. Comparing sub-lineage BA.2 to BA.1 studies mention transmission advantages for BA.2 rather than an increased immune escape and the severity of the disease is expected to be similar.
Overall, results show lower severity of infection, lower VE compared to Delta variant and importance of a 3rd dose. Nonetheless, vaccination, especially a 3rd dose, is essential to reduce the risk of severe courses and, thus, the level of population immunity is crucial to maintain the stability of health care systems without rigorous non-pharmaceutical interventions.
The possibility of relaxing non-pharmaceutical interventions can be attributed to high immunity levels within countries due to vaccination and prior infection and a lower risk of a severe course by Omicron. Nonetheless, immunity levels are expected to wane over time and, thus, a long-term vaccination strategy is necessary. On the one hand, vaccines can be adjusted to new variants that challenge current vaccines, on the other hand, future variants might turn out to be more severe than Omicron again. As data shows that protection is markedly increased by a three-dose regimen, vaccination commission should consider declaring three doses as full vaccination that should be obtained by everyone that can be vaccinated.