Ongoing trial show Pfizer COVID-19 vaccines remain highly effective after six months

The ongoing Phase 3 clinical trial of Pfizer/BioNTech's coronavirus vaccine confirms its protection remains high for at least six months after the second dose, the companies said Thursday.

Protection likely lasts even longer than that, vaccine experts say, but they say having data showing good protection six months after people were vaccinated is good news.

The vaccine remains more than 91% effective against disease with any symptoms for six months, the companies said in a statement. And it appeared to be fully effective against the worrying B.1.351 variant of the virus, which is the dominant strain circulating in South Africa and which researchers feared had evolved to evade the protection of vaccines, the companies said.

"The vaccine was 100% effective against severe disease as defined by the U.S. Centers for Disease Control and Prevention (CDC), and 95.3% effective against severe COVID-19 as defined by the U.S. Food and Drug Administration (FDA)," Pfizer and BioNTech said in a joint statement.