https://www.siliconvalley.com/2021/12/08/two-vaccine-doses-may-not-provide-sufficient-protection-against-omicron-coronavirus-variant-but-protection-improves-with-three-doses-pfizer-says/

Preliminary lab studies show two doses of the Pfizer/BioNTech vaccine may not provide sufficient protection against the Omicron coronavirus variant, but three doses are able to neutralize it, the companies said in a news release on Wednesday.

Samples from people who had two doses of the Covid-19 vaccine saw, on average, a more than 25-fold reduction in neutralization ability against the Omicron variant than the earlier virus, “indicating that two doses of BNT162b2 may not be sufficient to protect against infection with the Omicron variant,” the companies said.