A Third Dose of the Pfizer/BioNtech Covid-19 Vaccine Appears to “Strongly” Boost Protection Against the Delta Variant

 

July 28, 2021—New York—Pfizer posted data on a third, booster dose of the Pfizer/BioNtech vaccine, to be given at least 6 months after the second dose.

Antibody levels against the Delta variant in patients age 18 to 55 years who receive a third dose of vaccine are over five-fold greater than those following a second dose. Among patients age 65 to 85 years who receive a third dose, antibody levels against the Delta variant are over 11-fold higher than following a second dose.

The data, which have yet to be peer-reviewed and published, cite an "estimated potential for up to 100-fold increase in Delta neutralization after vs before the third dose."

Antibody levels against the original coronavirus variant and against the Beta variant, first identified in South Africa, were reported to be five to 10 times higher after a third dose than after a second dose.The tolerability profile of the third dose is consistent with that of the first two doses.

Data are from the global phase 3 portion of the clinical evaluation of the efficacy, safety, and tolerability of a third dose of the vaccine vs placebo. The efficacy of the third dose on continuing to prevent COVID-19 infection is being evaluated. The phase 3 study will enroll 10,000 participants from the original phase 3 trial.

Pfizer set off alarms by releasing data on a third dose prior to informing the CDC and NIH and has apologized.

Anthony Fauci, MD, Director of the National Institute for Allergy and Infectious Diseases and chief of the Laboratory of Immunoregulation, told CNN viewers to “listen to the CDC and not Pfizer when it comes to needing a Pfizer vaccine booster.”

Peter Hotez, MD, PhD, of the Baylor College of Medicine, Houston, told CNN viewers, “In the UK, Scotland, and Canada there are now three studies showing >80% protection, so pretty close to what we’ve seen. That’s the reason why we don’t need to be concerned right now about getting a booster.”

Reported protection against the Delta variant has been reported at 72% after one dose of the Moderna vaccine and 64% after two doses of the Pfizer/BioNtech vaccine. More data is needed on the protection afforded against the Delta variant by the Johnson & Johnson vaccine.

Pfizer and BioNtech expect to publish more definitive data about the analysis and to share all accumulated data as part of ongoing discussions with the FDA, EMA, and other regulatory authorities in the coming weeks. Application for emergency use authorization in the US is planned for August.

Regulators will determine whether, and which populations, may need a third dose of the Pfizer/BioNtech vaccine. If recommended, immunocompromised, older adults will receive it initially.

According to data published on July 20, 2021 by the CDC, emergence of the Delta variant, and associated rapidly increasing infections, represent approximately 83% of sequenced cases in the US.