Pfizer Says Booster Shot Protects Against Omicron

Pfizer announced that a booster dose of its COVID-19 vaccine offers strong protection against the Omicron variant. Lab studies indicate that a third dose generates neutralizing antibodies similar to those produced by two doses against the original virus. However, individuals with only the primary series showed a significant drop in antibodies against Omicron, suggesting that two doses may not suffice to prevent infection, though they might still avert severe disease.

What was observed in blood samples from individuals who received only the primary series of the vaccine?

What implications does the study suggest regarding the sufficiency of two doses of the vaccine against Omicron?