We Hoped a Covid Vaccine Would Be Effective. But 90% Efficacy Is a True Game-Changer.

What I hear in Pfizer’s promising vaccine news

Robert Wachter, MD


Photo: Kena Betancur/Getty Images

I can’t resist offering a few quick takes on the latest Pfizer vaccine news: 90% efficacy is far better than even the most optimistic projections. An election analogy that captures the “margin of victory” — these are like California results for Biden/Harris, rather than Pennsylvania results.

Efficacy and safety

The 90% refers to preventing symptomatic disease (that is, fever, cough). But we don’t know yet how well this vaccine prevents severe symptoms that lead to hospitalizations, ICU admissions, and death. Knowing that will be key. It seems likely it will hold up well, but that still needs to be demonstrated.

Now that the efficacy data are out, the next big question is safety. The need to wait two months to observe at least half the volunteers is the reason the vaccine won’t be ready to be considered by the FDA for an Emergency Use Authorization (EUA) until later this month. But there are some early signs regarding safety that are promising.

Namely, three other vaccine trials (conducted by Johnson & Johnson, Eli Lilly, and AstraZeneca) were suspended at various times to analyze safety concerns. The Pfizer study was never suspended, making it unlikely that we’ll see a high enough number of severe side effects to derail the vaccine’s eventual approval.

Even if there’s a rare side effect (which remains a possibility), 90% efficacy is so strong that the overarching risk-benefit equation will still be positive for use among at-risk populations. But for people at relatively low risk (of catching Covid and, if they do, of a bad outcome), we need to be sure it’s super safe.

While we’re most worried about severe side effects, it’s also good to know that the experience with the Pfizer vaccine to date is that the local reactions immediately after vaccination are relatively benign — perhaps a little worse than from the flu vaccine. While a more significant local reaction (that is, flu-like symptoms or pain at the injection site) might not prevent the vaccine from being approved by the FDA, it could discourage people from taking the vaccine, which would be problematic.

Supply, demand, and vaccine allocation

Pfizer has said that it can make 50 million doses available by year’s end, and 1.3 billion doses by the end of 2021. It’s a two-dose vaccine, so this means enough vaccine for 25 million people (who won’t all be in the U.S.) available by January. The math is clear: That’s a tiny fraction of the eligible population, meaning that we’ll need some kind of allocation scheme.

But before that, we’ve got to get the vaccine from the manufacturing plant out to doctors’ offices, pharmacies, and public health departments. Getting these doses packaged, frozen (at an ultra-low temperature, well below that of your kitchen freezer), shipped, and tracked is not a trivial undertaking. The Biden team will be brand new and this will be the 2021 Logistical Olympics. But, from his experience in running the stimulus program under Obama, we know that Biden is good at this, delegating to competent people and sweating the key details. This makes me far more hopeful about the logistics than I would have been under Trump. And yet, there are still bound to be hiccups.

The 90% refers to preventing symptomatic disease (that is, fever, cough). But we don’t know yet how well this vaccine prevents severe symptoms that lead to hospitalizations, ICU admissions, and death. Knowing that will be key.

Assuming that the vaccine crosses the FDA’s finish line (which I suspect it will in late November or early December), who will get it first? I expect the allocation will follow the outline published by the National Academy of Medicine, which prioritizes the vaccine by both exposure and risk. Phase 1 — the group likely to be first in line — will include frontline responders, people over 65 in congregate settings (such as nursing homes), or those with two or more chronic conditions. This group accounts for 15% of the population or 50 million people in the U.S.

Remember that there will only be enough vaccine to cover 25 million people by the end of 2020, and that much of the initial supply will go outside the United States. This means that, under ideal circumstances, we won’t see a large chunk of the American populace vaccinated until spring or summer (of course, other vaccines may work as well and shorten the timeline). Here’s a sobering thought: Given that it’s likely to be summer 2021 before most people are vaccinated, the time between now and then is about the same as the time between now and the start of the pandemic. In other words, we still have an awful lot of Covid, and deaths, ahead of us. Be safe!

The FDA and the central role of trust

Kudos to Pfizer for resisting the political pressure to rush this announcement. While some will undoubtedly claim that the timing, a week after the election, was far from coincidental, it’s not. November was when this analysis was supposed to come out; it was likely accelerated a bit by the surge in U.S. cases, which helped the trial reach its end points a little faster.

Kudos as well to FDA Commissioner Steve Hahn and the professional staff at the agency. History will treat them kindly for having done the responsible thing, at least on vaccines. An early hydroxychloroquine-like approval would have shattered public trust, and trust is everything when it comes to vaccines.

Speaking of which, I never bought the “50% of people won’t take a vaccine” mantra, despite what the polls said. How can one answer that question thoughtfully without knowing data on vaccine efficacy and side effects, and without witnessing the approval process?

If the vaccine is truly 90% effective, is shown to have few side effects (and no dire late complications), and is approved by the FDA via a credible process, I’d wager that the uptake will be more like 70%–80%. Why? This isn’t like childhood vaccines, given to prevent diseases you’ve never seen before and never heard about anyone dying of. Measles and other childhood diseases don’t wreck your life, screw up your travel, make you lose your job, or be unable to hug your grandkids. Of course, there’ll be anti-vaxxers, but they’ll be a fringe, marginalized minority.

Having Trump and team sidelined (though they’ll have their social media megaphone) will be helpful in efforts to avoid politicization of the vaccine. And watching how the media handled the Hunter Biden silliness (and is handling election results) gives one hope that their approach to baseless conspiracy theories has matured.

Trump, Biden, and vaccines

Speaking of Trump, one can only imagine how he feels with the news of the success of the Pfizer vaccine. After all, this was the “October surprise” that Trump was hoping for. The ultimate irony is that vaccines are the one part of the Covid response that the Trump administration got right, and their payoff — and all the praise and stock market elevations that will come with the rollout of a safe and effective vaccine — will be seen in the first days of Biden’s term.

(This is pulled and lightly edited from my November 9 Twitter thread.)



Robert Wachter, MD

Professor & Chair, Dept of Medicine, UCSF. What happens when poli science major becomes an academic physician. Thinks/writes on digital, quality, safety, Covid.