Whether vaccines need to be adapted to omicron depends on three things, says Rogier Sanders, professor of virology and experimental vaccinology at Amsterdam UMC. First: transmissibility. "Reports from South Africa seem to indicate that the virus is more rapidly transmissible than the delta variant, but we have to wait and see." The number of positive tests in South-Africa suddenly rose rapidly in recent weeks.

Second, to what extent does the virus cause milder or more severe disease than older variants? "We don't know anything about that yet," Sanders says. If you get much less sick from omicron, it could be a good thing if this variant spreads faster.

The third important question: is the new virus resistant to the immunity we have generated by vaccines or by previous infection? In other words, is omicron stronger than our protection? "I think we should assume that omicron is more resistant," Sanders says. The reason for his assumption comes down to the fact that omicron has mutated much more than the earlier variants. On the spike protein, with which the virus attaches to human cells, 32 changes were found compared to the original virus. That's far more than in previous variants. Current vaccines are designed to produce antibodies that target the spike protein. Marc Kaptein, the medical director of vaccine maker Pfizer Netherlands, thinks his vaccine is protective enough against omikron. "Until now, the vaccine has never had to be adjusted." Sanders is a bit more pessimistic. "The mutations in omicron we know in part from the beta variant. That one was less susceptible to the vaccines." Sanders: "We already see with delta that people who have been vaccinated twice do get infected, but the chance of them ending up in the hospital is extremely small."

Rogier Sanders was interviewed for Nieuwsuur about the new corona virus variant, the omicron variant. You can read the whole (Dutch) interview here.