Pfizer said it plans to submit data on a third dose of its COVID-19 vaccine to the FDA as soon as sometime in August, with anticipated approval before January.

That information came from an earnings call in late July, where early results of a trial on 6-month safety and efficacy of Pfizer-BioNTech’s BNT162b2 mRNA COVID-19 vaccine were revealed. As a preprint, the article had not yet been peer-reviewed, but it indicated a decline in effectiveness.

In the ongoing, placebo-controlled, observer-blinded, multinational, pivotal efficacy study, 44,165 participants aged 16 years and older, as well as 2,264 teens aged 12 to 15 years, were randomized to receive two doses, 21 days apart, of 30 μg BNT162b2 or placebo. Researchers were assessing vaccine efficacy (VE) against laboratory confirmed COVID-19 and safety data up to 6 months postvaccination.

The study concludes that BNT162b2 continued to be safe and well-tolerated. It found that VE against COVID-19 was 91% (95% CI, 89.0-93.2) through up to 6 months of follow-up, among evaluable participants and irrespective of previous SARS-CoV-2 infection. On the other hand, VE of 86% to 100% was seen across countries and in populations with diverse characteristics of age, sex, race/ethnicity, and COVID-19 risk factors in participants without evidence of previous SARS-CoV-2 infection.

Specifically, VE against severe disease was 97% % (95% CI, 80.3-99.9). In South Africa, where the SARS-CoV-2 variant of concern, B.1.351 (beta), was predominant, 100% (95% CI, 53.5, 100.0) VE was observed.

“With up to 6 months of follow-up and despite a gradually declining trend in vaccine efficacy, BNT162b2 had a favorable safety profile and was highly efficacious in preventing COVID-19,” the authors concluded.

During the earnings call, Mikael Dolsten, MD, PhD, who leads worldwide research, development, and medical for Pfizer, discussed research on a third booster shot of the vaccine to offset VE decline.

One finding was that a third booster dose of the Pfizer vaccine increases neutralizing antibody levels against the delta variant by more than five times compared with a second dose in adults aged 18 to 55 years. It appeared to be even more powerful for older adults aged 65 to 85 years, where the response was 11 times higher than after the second shot.

Israel recently announced it would be provided third Pfizer doses, but only to adults aged 60 years and older and immunocompromised patients. France also is offering the additional dose to immunocompromised patients.

The study involved only a few participants, however, including 11 in the 18 to 55 years age group and 12 in the 65 to 85 years age group.

“Receiving a third dose more than six months after vaccination, when protection may be beginning to wane, was estimated to potentially boost the neutralizing antibody titers in participants in this study to up to 100 times higher post-dose three compared to predose three,” Dr. Dolsten said in prepared remarks. “These preliminary data are very encouraging as Delta continues to spread.”

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