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FDA remains skeptical about booster shots despite new Pfizer data suggesting efficacy declines

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The US Food and Drug Administration (FDA) remains skeptical about vaccine booster shots against COVID-19 ahead of an advisory committee meeting on Friday, despite Pfizer-BioNTech releasing new data suggesting its need.

The Advisory Committee on Vaccines and Related Biological Products (VRBPAC) will meet at the end of the week to discuss data on potential third doses.

Members will vote on whether or not booster doses are safe and effective and whether they should be approved for all Americans.

Currently, the third doses are only approved for immunocompromised people in the US ages 12 and older.

New dates of Pfizer published on Wednesday suggests that the efficacy of the regular two-dose regimen decreases from 96.2 percent to 83.7 percent after six months, but that a booster dose increased the immune response.

However, in a separate briefing document Also published Wednesday, FDA officials have expressed doubts about the need for additional doses.

Documents ahead of an FDA advisory committee on COVID-19 vaccine booster shots were published Wednesday. Pictured: A nurse administers a COVID-19 booster injection to Lana Sellers in Altamonte Springs, Florida, Aug. 18

Pfizer has released new data indicating that the efficacy of two doses decreases from 96.2% to 83.7% after six months, but that third doses appear to increase antibody levels (above) five to 12 fold, especially in older adults

Pfizer has released new data indicating that the efficacy of two doses decreases from 96.2% to 83.7% after six months, but that third doses appear to increase antibody levels (above) five to 12 fold, especially in older adults

Last month, boosters were approved for immunocompromised Americans who had received either the Pfizer or Moderna vaccine after data showed they were less likely to develop high antibody levels after two doses.

At the time, Pfizer said the early data suggested that people given booster doses had a high level of protection between six and 12 months after their last dose.

The company filed for emergency booster dose approval in late August and submitted data that was made public on Wednesday.

The documents suggest that protection against two doses of the Pfizer vaccine drops from 96.2 percent seven days after dose 2 to 90.1 percent two months later to 83.7 percent up to six months later.

In addition, they cited data from Israel showing that people who were fully vaccinated in January 2021 had a 2.26-fold increased risk of breakthrough infections compared to those who were fully vaccinated in April 2021.

Another Israeli study mentioned in the documents showed efficacy against infection was 39 percent and against symptomatic diseases 40 percent from June 20, 2021 to July 17, 2021, when the Delta variant was the dominant strain.

By comparison, between January and April, these rates were 95 percent or higher.

Antibody levels appeared to increase 3.1-fold 28 days after dose three (far right) compared to day five after dose 2 (second from left)

Antibody levels appeared to increase 3.1-fold 28 days after dose three (far right) compared to day five after dose 2 (second from left)

The researchers say that while Delta was the dominant strain over the summer, the declining rates are a sign of declining efficacy of the vaccine, not the variant.

“As described…emerging data suggest that vaccine protection may wane approximately six to eight months after the second dose, and there is mounting evidence that booster doses of COVID-19 mRNA vaccines may be an urgent emerging problem for the public health,” the authors wrote.

The team also released data on a clinical trail with 23 participants who took part in Pfizer’s early-phase studies last year.

They had each received two doses of the vaccine and were given a booster dose at least six months later.

Of the participants, 11 were in the The group of younger adults ages 18 to 55 and 12 were 65 to 85 years old.

After the third dose, neutralizing antibodies to the original virus strain increased five-fold in the 18 to 55-year-old group and seven-fold in the 65 to 85-year-old group.

Against the Delta variant, antibody levels increased 5-fold in the younger adult group and 12-fold in the older adult group after booster injection.

In a separate paper, FDA scientists wrote with a skeptical tone about the need for booster shots.

“Overall, data indicates that current US-licensed or authorized COVID-19 vaccines still protect against severe COVID-19 illness and death in the United States,” the scientists wrote.

They added that studies of booster doses have produced conflicting findings and that “known and unknown biases may affect their reliability.”

In addition, the scientists pondered whether a third dose would increase the rate of rare heart infections — myocarditis and pericarditis — in young men after two doses.

“It is currently unknown whether there is an increased risk of myocarditis/pericarditis or other side effects after a booster dose,” they wrote.

“These risks and associated uncertainties must be taken into account when assessing benefits and risks.”

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