October's Pfizer's News

Dec 8, 2020

A newsworthy item to start the week! Pfizer, along with German drug maker BioNTech, announced the interim analysis of the research on whether their vaccine was successful in preventing COVID-19.

Alert! Alert! The vaccine is NOT approved. It is NOT available to anyone, not even POTUS.

As many of you have read, the vaccine was 90% effective in preventing infection. What this means is that there were 90% fewer infections in the group that got the vaccine vs. the group that didn’t. Let’s do some back-of-the-napkin math, not based on any numbers that have been made available. In a study of 40,000 people (approximately what Pfizer’s study has), 20,000 would receive the vaccine and 20,000 wouldn’t. For easy math, let’s estimate the prevalence of COVID-19 infections in the population studied to be 10%, so we would then expect 2,000 infections in the non-vaccinated group. In the other group, we’d see 90% fewer, or only 200.

In fact, what we know so far from Pfizer is that there have been 94 infections (and rising because of the surge!) in all participants in the study so far. If the vaccine were 100% effective, all of those infections would have been in the group that didn’t get the vaccine. At a 90% effectiveness rate, one can presume that around 9 of those infections were in the vaccinated group.

To put the vaccine effectiveness into context, the measles vaccine is over 90% effective in preventing the illness. This is why outbreaks of measles these days are extremely rare and only occur in communities where there are a large number of anti-vax parents. Remember, a virus needs a susceptible host, otherwise it can’t propagate. Let’s say I’m ill with COVID (or measles) and don’t know it. If I get into an Uber in a community that is fully vaccinated with a vaccine that is 90% effective, there is only a 1 in 10 chance that this driver would be susceptible to my illness. If I subsequently get into close contact with just two coworkers the rest of that day, odds are that I wouldn’t have encountered a single susceptible person. Where we are now? In most places in the US there is somewhere between a 90 to 100% chance that the driver and my coworkers would be susceptible hosts and at risk for getting the illness. I’ve then just become a super spreader.

On the flip side, the flu vaccine is only 40-60% effective, partly because the influenza virus has a high mutation rate, unlike SARS-CoV-2. Despite our vaccination efforts we still have a flu season every year.

An effective vaccine can snuff out a virus.

Should we be excited about this report? Yes! They are very promising data at first blush.


  1. Confirmation: This announcement was made by the CEO of Pfizer, not through an independent analysis of the data. Experts need to see the data to check it. I heard that the trial had to be extended because there weren’t enough infections yet. Data scientists need to confirm that the data are powerful enough to show a difference between the two groups. We’ve seen some COVID-19 research and analysis that has had to be walked back once a closer look was taken.

  2. Confirmation #2: One of the other important factors that the FDA is considering before approving the vaccine is whether the vaccine decreases the severity of COVID-19 in those who get the illness despite vaccination. This is what happens with the flu vaccine: you may still get the flu but it’s not as bad. What happened to the estimated 9 people who get COVID-19 even though they got the vaccine? Mild illness? ICU?

  3. Harms: The Phase 3 trial isn’t complete with just data on effectiveness. We need to know harms. The FDA is appropriately requiring at least two months of observation before applying for approval (“FDA Approved”) or emergency use authorization (“EUA”). Keep in mind this is a completely novel method of vaccine production. While mRNA vaccines have been studied for the past decade, this would be the first such vaccine to be released into the marketplace. In theory, it’s likely safer than the flu vaccine with regard to how it is made, but we just don’t know for sure yet.

  4. Access: The Feds have bought 100 million doses of the vaccine supply for distribution through their Warp Speed program. (Pfizer is only getting $19.50 per vaccine which is a very low cost for a vaccine. Frame of reference: we pay about $150 for each shingles vaccine.) For other vaccines such as flu, shingles and pneumonia, Stephanie buys them directly from the manufacturers, Pfizer included. Will there even be COVID-19 vaccines for purchase? We don't know.

  5. Storage: Even if we could get the vaccine, we have nowhere to store it. The Pfizer mRNA vaccine needs to be kept VERY VERY cold. Something like -70 degree Celsius. There’s actually a large deep-freeze facility in Kalamazoo (shout out to Charles and Laura!) that is storing a good percentage of the 10s of millions of doses of the Pfizer vaccine prior to distribution. The freezer in our offices where we keep measles vaccines, actually, only goes to about -25 degrees. You need a special kind of freezer to store this novel vaccine, and no doctor’s office will have one. The Mayo Clinic doesn’t even have one of these types of freezers.

  6. Distribution: The Feds via Warp Speed are planning to distribute the vaccine to the public somewhere in the “public square.” Where? Unsure. Will you line up alongside a stranger in the cold to get this? And you’ll need to do it twice since the Pfizer vaccine takes two doses three weeks apart to be effective. The details of distribution logistics are unknown, but are extremely complex. This past Sunday’s 60 Minutes episode had a segment on Project Warp Speed and outlined some of the distribution challenges.

  7. Who: Since the Feds are distributing the initial wave of vaccine, it remains to be seen who will get access to it. Pfizer says they'll have 10s of millions of doses (remember two per person needed) by the end of the year. We need to vaccinate in the hundreds of millions of people.
    Who first? Age? First responders? Front line health care workers? Nursing home residents? I know we’re all eager to get to a new normal, but when it does become available we need to be mindful that we don’t take the vaccine from someone more vulnerable.

  8. When: So, when is this all going to happen? We need a few more weeks to a month to get the final harm data from Pfizer. Pfizer is then going to submit an application for Emergency Use. For safety reasons the FDA will then need time to review this application. NEVER has a vaccine been approved using the EUA designation. Since we’d be giving a vaccine to a healthy person to prevent disease, the FDA wants to be extremely mindful that they don’t approve a dangerous agent.

Despite Pfizer and the public’s eagerness, don’t be surprised if the vaccine gets delayed for more data on harm to come through. That all being said, we may see the first wave of vaccines provided to a subset of the population before the turn of the new year. I hold to my prior estimate that most of our patients won’t have access to a vaccine until the spring.

So, while the announcement from Pfizer was exciting and promising, there’s still some runway left and the path ahead is not fully lit. We will continue to follow closely.

More to come,

Dr. Will

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