Phil Seo, MD, MHS
“It’s like winning Powerball.”
For months, there has been a steady trickle of questions from my patients, asking for my opinion about the new vaccines being developed to prevent COVID-19. More to the point, they want to know if they should be vaccinated.
After some fits and starts, I finally struck upon a pat answer that I liked: “It’s a little bit like asking me how you should spend the money you’re going to win by playing Powerball. There are more than 200 vaccines under development. Let’s just see what happens.”
Looks like that answer won’t cut it anymore.
On Nov. 16, Moderna announced the results of its COVE study, and the world, collectively, breathed a sigh of relief.
The COVE study examined the efficacy of the Moderna vaccine candidate at preventing COVID-19.1 More than 30,000 participants were enrolled, 95 of whom were subsequently diagnosed with COVID-19. All but five of those patients had received a placebo, indicating the vaccine was 94.5% effective at preventing patients from developing COVID-19. The most common, medically significant (i.e., Grade 3) adverse events were fatigue, myalgias and arthralgias, which are not all that surprising for a vaccine study.
On Nov. 18, Pfizer and BioNTech announced the results of the phase 3 study of their COVID-19 vaccine candidate.2 Of the 43,661 participants, 170 patients were eventually diagnosed with COVID-19. Only eight of those patients had received the vaccine, meaning it was 95% effective at preventing the disease. The most common medically significant adverse events were fatigue and headache, which again, seem like a small price to pay for immunity against SARS CoV-2.
On Nov. 23, AstraZeneca also came through with good news, sort of. Unlike the Moderna and Pfizer vaccines, which use mRNA to trigger an immune response, the AstraZeneca vaccine uses a modified adenovirus to deliver the goods.
When administered to 8,895 volunteers, the AstraZeneca vaccine was 62% effective at preventing COVID-19.3
That’s above the 50% efficacy threshold announced by FDA Commissioner Stephen Hahn as the minimum a vaccine would need to achieve to win FDA approval.4 And it is certainly better than 0%, which is the amount of protection that most of us currently have against COVID-19.
Fortunately, AstraZeneca made a mistake. The first 2,741 patients enrolled in the study received a lower dose of the vaccine than originally planned.5 Because the error was not felt to impact the vaccine’s safety, the study was allowed to continue. That was a truly brilliant decision, because it turns out that the lower dose of the vaccine was 90% effective at preventing COVID-19, which brings it in the ballpark of the other two vaccines.
