healthHealth and Medicine

Pfizer COVID-19 Vaccine Reported As 100 Percent Effective In South African Trial Participants


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockApr 1 2021, 14:54 UTC
COVID-19 vaccine

The new data has also confirmed its high efficacy in preventing severe forms of the disease. Image Credit: noamgalai/

Pfizer and BioNTech have announced new results from their clinical trial, showing 100 percent efficacy at preventing COVID-19 cases in South Africa, where variant B.1.351 is prevalent. The new data has also confirmed its high efficacy in preventing severe forms of the disease, which has so far killed 2.8 million people around the world at the time of writing. 

The vaccine is also 100 percent effective in preventing severe cases as defined by the US Centers for Disease Control – or 95.3 percent effective against severe cases if we are to follow the definition of the US Food and Drug Administration.


The companies report that they have evaluated the data from over 44,000 participants aged 16 years and older. The data also includes an analysis of over 12,000 vaccinated participants that had a follow-up after a second dose. The efficacy between seven days to six months after the second dose is 91.3 percent. The longevity of the immune response is truly good news.

“These data confirm the favorable efficacy and safety profile of our vaccine and position us to submit a Biologics License Application to the U.S. FDA,” Albert Bourla, Chairman and Chief Executive Officer of Pfizer said in a statement. “The high vaccine efficacy observed through up to six months following a second dose and against the variant prevalent in South Africa provides further confidence in our vaccine’s overall effectiveness.”

The part of the trial from South Africa involved 800 participants. There were only nine cases of COVID-19, and they all happened in the placebo group. Six of those cases were confirmed to be of the B.1.351 lineage, which caused concerns when it was first discovered as vaccines were not designed with this mutation in mind.


“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,” added Dr Ugur Sahin, CEO and Co-founder of BioNTech. “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.”

The new results strengthen the high efficacy of the vaccine that has been reported in previously published data as well as general population analyses. Data from Public Health Scotland showed that the hospitalization rate of those that received just the first dose of the Pfizer/BioNTech vaccine was reduced 85 percent compared to the general unvaccinated population.

For more information about COVID-19, check out the IFLScience COVID-19 hub where you can follow the current state of the pandemic, the progress of vaccine development, and further insights into the disease.

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