Quote:Mikael Dolsten, Pfizer's chief scientific officer, told Insider the drugmaker was already preparing for the worst-case scenario: A shot specific to the Omicron variant will be needed. But before he draws that conclusion, Dolsten is watching how two unknown elements play out in the next few weeks, he said.

The first unknown is how well the current vaccines hold up against Omicron. The answer won't be a binary yes or no but a sliding scale of protection.

Experts generally do not anticipate that Omicron will completely evade all protection from the current shots. Previous research suggested many more mutations were needed to reach that point.

But other variants of concern, including the Beta and Delta strains, have shown they can diminish vaccine protection. Omicron may be more concerning because it has far more mutations on the spike protein, which is the target of vaccines.

Most experts expect Omicron to decrease levels of neutralizing antibodies, virus-fighting proteins that play a key role in our immune response. The question that laboratory testing will help answer is just how much of a decline this variant can cause.

Dolsten said a tenfold decrease in antibodies would make him concerned that the current vaccines wouldn't be sufficient and an Omicron-specific shot would be needed.