New research suggests that three doses of the Pfizer/BioNTech coronavirus vaccine offers significant protection against the quickly spreading Omicron variant of the virus, according to laboratory results released Wednesday by the companies. Tests of blood from people who received only two vaccine doses showed much lower antibody levels against Omicron compared with an earlier version of the virus — an indication that two doses alone “may not be sufficient to protect against infection” by the new variant, the companies said. While the experiments, conducted with blood samples in the lab, may not reflect how the vaccines will perform in the real world, they do suggest that boosters are likely to protect people. Other studies are underway to assess the effectiveness of the other COVID-19 vaccines against the Omicron variant.