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S. African Variant Challenges Pfizer, Moderna Vaccines

photo of pfizer vaccine

March 9, 2021 -- The Pfizer/ and Moderna vaccines don’t work as well against the coronavirus variant first discovered in South Africa as they do against the dominant virus strain first seen in United Kingdom, a new study says.

In the study, 10 blood samples were taken from people who received the Pfizer vaccine, 28 days after the second dose, and 12 samples from those who received the Moderna vaccine, 43 days after the second dose, Business Insider reported, citing a study published in Nature.

The goal was to find out how well the blood sample antibodies “neutralized” the original coronavirus, the variant from South Africa (called B.1.351), and the variant found in the U.K. (B.1.1.7).

The key finding: The percentage of positive antibodies that neutralized the South African variant was 12.4 fold lower for the Moderna vaccine than against the original coronavirus and 10.3 fold lower for the Pfizer vaccine, the study says.

The researchers found that the two vaccines still appear to work well against the variant first found in the U.K.

“Overall, the neutralizing activity against B.1.1.7 was essentially unchanged, but significantly lower against B.1.351,” the study said.

Both Pfizer and Moderna have previously said their vaccines work better against the U.K. variant than the South African variant.

The new lab study differed from previous studies because it used real forms of the variant taken from people who’d been infected with the virus. Earlier studies used manufactured forms of the South African variant and showed a higher level of effectiveness for the vaccines.

The variant first detected last fall in South Africa has now been reported in several countries. The CDC says that in the United States, 81 cases have been found in 20 states.

More than 3,000 cases of the UK variant have been found in the U.S., with every state except Vermont, South Dakota, and Oklahoma reporting cases as of March 8, the CDC says. Health experts say it may soon become the dominant coronavirus strain in the country.

Researchers acknowledged the sample size was small and it’s not fully known how the Pfizer and Moderna vaccines will work in real life against the South African variant. Both companies have said they’re developing booster shots targeted for the South African variant.

A Second Study

A different study came to a slightly different conclusion about the Pfizer vaccine, Bloomberg reported.

That study showed the Pfizer vaccine effectively neutralized the coronavirus strain first detected in Brazil, as well as the U.K. variant, and had a “robust but lower” effectiveness against the South Africa variant, according to a letter to the New England Journal of Medicine.

Bloomberg said the study tested samples taken from people at least 2 weeks after they received their second Pfizer shot -- against viruses engineered to have mutations from the three virus lineages.

EmailBloomberg                        While encouraging, the findings “must be validated by real-world evidence,” the letter says.

The research was performed by scientists at the University of Texas Medical Branch in Galveston, and was supported by Pfizer and BioNTech.

The CDC says 15 cases of the Brazilian variant have been found in nine states.

WebMD Health News Brief

Sources

Business Insider: “A new lab study shows troubling signs that Pfizer's and Moderna's COVID-19 shots could be far less effective against the variant first found in South Africa”

Nature: “Antibody Resistance of SARS-CoV-2 Variants B.1.351 and B.1.1.7”

CDC: “US COVID-19 Cases Caused by Variants.”

Bloomberg: “Pfizer-BioNTech Covid Shot Neutralizes Brazilian Strain in Lab”

New England Journal of Medicine: “Neutralizing Activity of BNT162b2-Elicited Serum”

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