Fantastic news: Does the Pfizer vaccine work?

Best pandemic news to date

I’m getting more excited by the minute as I write this.

Pfizer (US multinational pharma) and BioNTech (German pharma) are collaborating on a COVID-19 vaccine. Today they announced efficacy data from their phase 2/3 vaccine trial, and it’s astonishingly good. Comparing vaccinated trial participants with those who received placebo, the vaccine reduced symptomatic coronavirus infections by 90%. The threshold for FDA emergency use authorization is 50%.

This does not mean “we have a vaccine.” (I’ll dissect that phrase in my next blog posts.) But it suggests that whatever vaccines do go into distribution in the next few months (weeks?) have a better chance of being highly effective than I expected. There had been a lot of uncertainty about whether any SARS-CoV-2 vaccine would work at all (there are several ways to define whether a vaccine “works”). You can’t predict this stuff. You have to do the experiment. And it looks like the experiment is giving the answer we hoped for.

Reality being far more complicated than a soundbite, there are, of course, a long list of caveats, qualifiers, and details. (Read this excellent STAT News article for more.) Nevertheless, this is unquestionably hopeful news. It’s also a testament to the prowess of Pfizer as a driver of research-the company rejected federal money for research and development from the Warp Speed program, investing billions of its own dollars instead. Warp Speed did, however, sign a contract with Pfizer this past summer, promising to purchase 100 million doses of their vaccine. That is looking like a good bet.

Pfizer’s data on efficacy is not only unexpectedly good, it’s unexpectedly strong from a statistics point of view. You need to understand that the answers to questions like, “Does the vaccine work?” and “Is the vaccine safe?” are far from black-and-white. The answers are not “yes” or “no.” They’re probabilities. So when a clinical trial is designed, the designers make choices that affect the strength of their answers. For example, more people participating in a vaccine trial gives a statistically stronger answer than fewer people. Likewise, a trial that lasts six months gives a stronger answer than a trial that lasts two months (all other things being equal). In that context, all the COVID vaccine trials in the US and Europe are getting an ironic boost from the current surge in coronavirus infections. The answer to the question, does this vaccine prevent infection? is statistically more powerful when the infection is prevalent than when infections are rare. This is the one “good” thing about the surge.

Efficacy is half of the vaccine challenge. Safety is the other. A vaccine that protects against coronavirus infection but makes people sick is useless. So the next critical step for the Pfizer vaccine is a report on safety. According to STAT News, Pfizer has designed their clinical trial to report on safety “when half of the patients in their study have been observed for any safety issues for at least two months following their second dose. Pfizer expects to cross that threshold in the third week of November.”

Let me tell you, I will be watching for that report with great, great interest. This could be a staggering scientific achievement-with a lot of luck involved too.

What’s the accomplishment? First of all, speed. The fastest a vaccine has ever been developed before is four years. Vaccines against the new SARS-CoV-2 coronavirus were created in under four months. What’s taking longer is figuring out whether those vaccines work and are safe to give to otherwise healthy people. This was possible because of the ease with which scientists are able to identify new viruses, and to sequence their genomes. A COVID vaccine will be one of the fruits of the genomic revolution of recent decades.

Second, this could be an achievement of new biotechnology. The Pfizer/BioNTech vaccine is a type of vaccine that has never been approved for humans before. It uses RNA from the virus to vaccinate against it. (I’ll talk more about tech details in upcoming post.) Pfizer’s isn’t the only COVID vaccine in advanced phase testing that uses this new RNA technology. Moderna’s vaccine does too. So today’s news is also hopeful for that vaccine.

I’ll put in a plug here for federal funding of basic science. What Pfizer and the other pharma companies are accomplishing here is built on basically a century of government-sponsored biomedical research. That science put us in a position to look at the gene sequence of the new virus and deduce which bit of it could be useful to generate an immune response.

If the Pfizer vaccine eventually gets approved for emergency use, it does pose two logistical challenges. The vaccine will be given as two doses, not just one. And because of the delicate chemistry of RNA, the vaccine must be constantly and carefully stored at ultracold temperatures. That means getting the vaccine into people’s arms can only happen at locations with specialized equipment-not, for example, your local supermarket pharmacy.

Throughout this pandemic, much of our emotional energy has been spent on projections of the future. How will the virus behave? What impact will our non-pharmaceutical interventions have? Will our hospitals overflow? How many people will die? Will there be a vaccine? Often those projections have been disheartening. Of necessity, we’ve had to always consider worst-case scenarios, even if those scenarios are not the most likely.

At this moment in the pandemic, the short-term outlook is grave. So let’s allow ourselves to indulge in some psychic healing and hope. Let’s savor the possibility of a best-case scenario, a safe, effective vaccine that goes into distribution in as little as two months from now.

I’ll raise a glass to that.

Amy Rogers, MD, PhD, is a Harvard-educated scientist, novelist, journalist, and educator. Learn more about Amy’s science thriller novels, or download a free ebook on the scientific backstory of SARS-CoV-2 and emerging infections, at

Originally published at on November 9, 2020.

Amy Rogers, MD, PhD, is a Harvard-educated scientist, novelist, journalist, and educator. She blogs about coronavirus at

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