FDA says Pfizer`s new flu shot fails trials

Pfizer’s experimental mRNA influenza vaccine will not advance toward approval without new evidence that it protects older adults, according to comments from the head of the U.S. Food and Drug Administration.

FDA Commissioner Dr. Marty Makary said on Fox News on Nov. 29 that the shot “failed in seniors.” He said the clinical trial showed “zero benefit” for people aged 65 and older and that the agency would not authorize products that do not demonstrate effectiveness.

Pfizer did not comment on the remarks.

A recent paper in the New England Journal of Medicine reported that the vaccine outperformed an already-licensed product among healthy adults aged 18 to 64. The paper did not disclose that in adults 65 and older, 0.5 percent of vaccinated participants developed influenza-like illness with laboratory-confirmed influenza, the same rate seen in the control group.

Trial data posted earlier this year on ClinicalTrials.gov also showed higher levels of reported reactions among older adults. Within seven days of vaccination, 68.7 percent of seniors who received the experimental shot reported adverse reactions, compared with 25.8 percent of those who received the licensed vaccine.

Independent journalists and members of the Centers for Disease Control and Prevention’s vaccine advisory panel drew attention to the senior results after the NEJM paper was published. Retsef Levi, a professor at the Massachusetts Institute of Technology, said in an email that the omission represented a serious failure of the peer-review process. A spokesperson for the journal said the study authors were best positioned to address questions about the data. The corresponding author did not respond.

Makary’s comments followed a memorandum from Dr. Vinay Prasad, who leads the FDA’s Center for Biologics Evaluation and Research. He wrote that the agency will revise its framework for influenza vaccines, describing current evidence as weak and relying on uncertain measures of effectiveness. He said officials plan to require randomized trials that demonstrate efficacy through clinical outcomes.

The FDA’s existing process allows yearly approval of updated flu shots. The agency states that approved vaccines are safe and effective, and CDC estimates place flu vaccine effectiveness since 2009 between 19 percent and 60 percent.

Dr. Robert Malone, who heads the CDC advisory panel’s influenza workgroup, said the memorandum signifies major disruption to the annual flu vaccination system.