Is the Pfizer mRNA vaccine losing its effectiveness?

Surveillance data collected in Israel from June 6 through early July 2021 showed that the Pfizer vaccine was only 64% effective in preventing COVID-19 infections and symptomatic illness. Should we be worried?

This effectiveness is notably lower than earlier reports of real-world efficacy of the Pfizer vaccine.

This decline has coincided with the increased prevalence of the Delta variant and cessation of nearly all social distancing restrictions and mask-wearing requirements in Israel.

Nevertheless, and of greatest import, the vaccine was estimated to be 93% effective in preventing hospitalization and severe illness.

Scientists in the UK studied the relative effectiveness of two-shot mRNA vaccines such as those of Pfizer and Moderna versus the Alpha and Delta variants.

They found the vaccines to be 80% effective in stopping symptomatic disease from the Delta variant – that’s compared to 88% effectiveness of the vaccines against the Alpha variant.

But, like in Israel, the mRNA vaccines stopped hospitalization for both Alpha and Delta variants more than 90% of the time.

But whereas the first vaccine dose was 49% effective against the Alpha variant, one dose only stopped the Delta variant 31% of the time. The second shot was critical, the researchers found.

The bottom line is that the Pfizer mRNA vaccine may be less effective against the Delta variant but still is dramatically effective in preventing severe illness, hospitalization, and death.

This report is translated from Hebrew in the State of Israel Ministry of Health, 7/5/21.


This blog was accurate as of the day of posting. However, as the COVID-19 pandemic rapidly evolves and the scientific community’s understanding of the novel coronavirus and the COVID vaccine develops, the information above may have changed since it was last updated. While I aim to keep all of my blogs on COVID and the COVID vaccine up to date, please visit online resources provided by the CDC, WHO, and your local public health department to stay informed on the latest news.

© Copyright WLL, INC. 2021. This blog provides a wide variety of general health information only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment from your regular physician. If you are concerned about your health, take what you learn from this blog and meet with your personal doctor to discuss your concerns.

 

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