Pfizer Shot Provides Partial Omicron Shield in Early Study (2)

Pfizer Inc.’s vaccine provides less immunity to the omicron variant than to other major versions of Covid-19, according to laboratory experiments that still indicated a third dose may help stop the highly mutated strain.

Researchers at the Africa Health Research Institute in Durban, South Africa, found omicron resulted in about a 40-fold reduction in levels of neutralizing antibodies produced by people who had received two doses of the Pfizer-BioNTech SE shot, compared with the strain detected in China almost two years ago.

The loss of immune protection is “robust, but not complete,” Alex Sigal, head of research ...