Pfizer’s COVID-19 booster effectively blocks Omicron variant, lab tests show

Pfizer Inc. and BioNTech SE said that a third dose of their Covid-19 vaccine neutralized the Omicron variant in lab tests but that the two-dose regimen was significantly less effective at blocking the virus.

The companies said that tests of blood from people who had received only two doses found much lower levels of antibodies protecting against Omicron than against an earlier version of the virus. That suggests that two doses “may not be sufficient to protect against infection” by the new variant, the companies said.  The companies examined 39 samples.

Health departments are identifying close to 100,000 cases a day, hospitalizations are ticking up and deaths are again on the rise in the United States, almost all due to the Delta variant.

The CDC had recorded 43 cases of Omicron infection, most of them mild, in about 20 American states as of Wednesday, the Associated Press reported. Cases are rising much faster in parts of South Africa and Europe; early modeling and analysis suggest that this latest variant may spread quicker than delta. 

In South Africa, where Omicron already appears to be dominant, two large hospitals are reporting more children testing positive for the coronavirus after being admitted for other reasons, suggesting increased community transmission there.

President Biden spoke out to draw attention to Pfizer-BioNTech’s findings on Wednesday, calling them “very, very encouraging” and saying they showed that the vaccines remain a bulwark against the virus.

“If you get the booster, you’re really in good shape,” Mr. Biden said. According to federal data, the United States has more than 200 million fully vaccinated people, but only about 50 million have gotten a booster dose.