Phase 3 vaccine trials in the U.S. July 27-Aug. 20/21: A timeline

Phase 3 COVID-19 vaccine trials in the United States began July 27 with both the Moderna vaccine and the Pfizer/BioNTech vaccine.

Given that both vaccine studies are (separately) enrolling 30,000 volunteers (half receive placebo), and given that both require two doses separated by either 28 days (Moderna) or 21 days (Pfizer/BioNTech), then the timeline for completing enrollment for the first dose bears watching in order to estimate when the second dose will be completed for all 30,000 volunteers in each of these two studies.

Full safety assessment, immunogenicity measures, and Vaccine efficacy (Ve) determination will require some time after the second dose is given.

• Moderna: According to Moderna's COVID candidate vaccine website:13,194 participants enrolled in the COVE Phase 3 Study as of Friday, August 21, 2020 at 5:00 pm ET”. The website also states: “As of Friday, August 21, Black or African American, Latinx, American Indian and Alaska Native participants make up approximately 18% of all participants in the Phase 3 study.” The protocol for the Moderna vaccine candidate is available on the ClinicalTrials.gov website.
• Pfizer and BioNTech: According to their August 20 statement, their COVID candidate vaccine Phase 3 trial has enrolled 11,000 of the planned 30,000 volunteers. “Assuming clinical success, Pfizer and BioNTech are on track to seek regulatory review of BNT162b2 as early as October 2020 and, if regulatory authorization or approval is obtained, currently plan to supply up to 100 million doses worldwide by the end of 2020 and approximately 1.3 billion doses by the end of 2021.” The protocol for the Pfizer/BioNTech Candidate is on Clinical trials.gov. Note: Phase III trial will use “a 2-dose (separated by 21 days) schedule”. In a July 27 press release Pfizer and BioNTech stated they could seek an FDA “Emergency Use Authorization or some form of regulatory approval as early as October 2020”

Given that from July 27 to August 21 neither the Moderna or Pfizer/BioNtech Phase III studies had reached 50% enrollment, then even if enrollment is completed for the first dose by mid-September, the second dose (given 21 or 28 days after the first dose) will likely not be completed for all 30,000 enrollees in each Phase III study until mid-October. This assumes that full enrollment, and giving both doses, is not delayed for any reason in either Phase III study.

If these timelines prove to be accurate, then for this writer (a former FDA vaccine medical official and US Public Health Service officer in the 1990s) a path for the U.S. Food and Drug Administration to establish that adequate data on safety and efficacy exists for either of these vaccines to receive an FDA Emergency Use Authorization by Halloween is difficult to envision, and seems unlikely by Thanksgiving.