FDA expands probe into safety of AstraZeneca's COVID-19 vaccine

The FDA has expanded its investigation into AstraZeneca’s COVID-19 vaccine to include data from clinical trials of prophylactics based on the same viral vector platform, Reuters reports

AstraZeneca quickly gained regulatory clearance to resume dosing in the U.K. part of its development program after a case of transverse myelitis triggered a clinical hold. Regulators in Brazil, India and South Africa have also given AstraZeneca the green light to resume. However, the U.S. phase 3 is still on hold.

The FDA reportedly wants to see data from trials of similar vaccines before lifting the clinical hold. AstraZeneca’s COVID-19 vaccine AZD1222 was created by a team at the University of Oxford that previously used the same ChAdOx1 engineered chimpanzee adenovirus in other prophylactics designed to offer protection against infectious diseases including Chikungunya virus, seasonal influenza, malaria, Middle East respiratory syndrome, tuberculosis and Zika virus. 

Earlier and ongoing trials of the use of the ChAdOx1 vector to protect against diseases other than COVID-19 are far smaller than the SARS-CoV-2 studies now underway. Even so, the trials still provide close to a decade of experience of the effects of administering ChAdOx1-based vaccines to humans. The FDA reportedly wants to factor that experience into thinking about AZD1222.

Researchers are reportedly expected to get the requested data to the FDA this week. However, some of the data are in a different format than the one typically used by the FDA, potentially complicating efforts to quickly review the information and decide on the next steps for AZD1222. 

The report of the FDA request for more data comes weeks after a director at the National Institutes of Health said leaders at his employer are “very concerned” by the adverse event in the AstraZeneca trial. The director also called for AstraZeneca to be “more forthcoming.”

While the U.S. trial of AZD1222 is on hold, the developers of other leading COVID-19 vaccines are racing toward pivotal data. The Pfizer-BioNTech collaboration and Moderna now have sizable leads over AstraZeneca in the U.S.