The FDA advisory panel charged with making a recommendation regarding emergency use for the Pfizer vaccine convened earlier today. After a packed scheduled which included a presentation by Pfizer, public comments, and an FDA discussion of their review process, 77% of the 23-member panel answered affirmatively to the question of whether the benefits outweighed the risks for use of the Pfizer product in individuals 16 years of age and older. When asked about the timeline for the final approval, an FDA spokesperson indicated that final Emergency Use Authorization could come in a few weeks but then corrected herself, suggesting the agency may make its decision in just a few days.
The pharmaceutical giant came prepared to defend its blockbuster drug. Contrary to its initial government filing which can be found on clinicaltrials.gov, Pfizer had data on most categories excluded from the original research design. While efficacy and safety findings on individuals with co-morbidities including hypertension and obesity were reassuring, it is clear that the drug company must continue its research and closely monitor the data long-term as the vaccine is rolled out to the community.
Pfizer offered more granular data that revealed that the percentage of study participants over the age of 65—the typical age bracket that defines the elderly in trials—was 16.7%, well below the 45% touted in Pfizer press releases that redefined the elderly as anyone 56 years old and above. This smaller sample size of the age with the weakest innate immune response demands consideration as the first doses are administered to the elderly care homes. If any single demographic is likely to see a drop in the whopping 94% efficacy claimed by the drug manufacturer, it will probably be this group.
Most of the concerns voiced during the advisory meeting revolved around safety, while the study design and the effectiveness of the vaccine received few challenges. Nevertheless, there were some red flags. Pfizer’s own data showed that a large number of those who received the experimental vaccine had telltale reactions. For example, approximately 30% in the experimental arm experienced chills, compared to about 3% who were given the placebo. These were minor reactions but may have allowed investigators to infer who had received the actual drug. If the blinding was affected, then researchers may have ordered more testing, which was left to the discretion of investigators, for the placebo group which could have, in turn, distorted the figures of vaccine effectiveness.
Also worth noting is the fact that the percentage of participants to contract the infection, both in those who got the real vaccine and the placebo arm, was lower than expected. As one panel member astutely pointed out, this potentially indicates volunteer bias. In other words, if a high percentage of clinical trial participants were unusually scrupulous regarding use of NPI measures such as social distancing and mask wearing, this also could have had the effect of inflating overall efficacy rates.
While the FDA pauses before issuing an inevitable approval, on the other side of the pond thousands of UK care home residents and medical professionals have already received the first doses of the Pfizer vaccine. Alarmingly, by the second day of the vaccination program, two healthcare workers had already experienced allergic reactions to the shot which resulted in life-threatening anaphylaxis. Absent from Pfizer’s clinical trials, these severe adverse events early in the British vaccination program beg the question of whether or not the study design generated accurate findings or strategically guided evidence to facilitate approval and enhance marketability. For many of us scrutinizing the details behind this developing story, it is hard not to wonder if more unpleasant revelations might lie ahead.