Pfizer says its COVID-19 vaccine is still highly effective after 6 months

The COVID-19 vaccine from Pfizer and BioNTech is highly effective against symptomatic COVID-19 for at least six months after a second dose, a new analysis has shown.

The companies on Thursday announced that in an analysis of its phase 3 study that included 927 symptomatic COVID-19 cases, the vaccine was 91.3 percent effective "measured seven days through up to six months after the second dose." It was also 100 percent effective against severe disease as defined by the CDC, as well as 95.3 percent effective against severe disease as defined by the FDA, the companies said. There were no serious safety concerns.

Additionally, Pfizer and BioNTech said the vaccine was 100 percent effective against COVID-19 cases in South Africa, where a concerning variant has been spreading.

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The analysis comes after a CDC study earlier this week showed the Pfizer and Moderna COVID-19 vaccines to be highly effective at preventing infections in real-world conditions, as well as after Pfizer said Wednesday a trial showed its vaccine to be 100 percent effective in adolescents aged 12 to 15.

"It is an important step to further confirm the strong efficacy and good safety data we have seen so far, especially in a longer-term follow-up," BioNTech CEO Ugur Sahin said. "These data also provide the first clinical results that a vaccine can effectively protect against currently circulating variants, a critical factor to reach herd immunity and end this pandemic for the global population."