Pfizer says COVID-19 booster offers protection against Omicron

Pfizer said Wednesday that a booster dose of its COVID-19 vaccine may offer important protection against the new Omicron variant even though the initial two doses appear significantly less effective.

Pfizer and its partner BioNTech said that while two doses may not be protective enough to prevent infection, lab tests showed a booster increased by 25-fold people's levels of virus-fighting antibodies against the Omicron variant.

Blood samples taken a month after a booster showed people harboured levels of Omicron-neutralizing antibodies that were similar to amounts proven protective against earlier variants after two doses.

Scientists don't yet know how big a threat the Omicron variant really is. Currently the extra-contagious Delta variant is responsible for most of the COVID-19 cases in the U.S. and other countries.

But the Omicron variant, discovered late last month, carries an unusually large number of mutations and scientists are racing to learn how easily it spreads, whether it causes illness that is more serious or milder than other coronavirus types -- and how much it might evade the protection of prior vaccinations.