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Comment by jostmey | Hacker News Reader

I just read that Pfizer reports its vaccine as 95% effective, even though pharmaceutical originally reported its vaccine as 90% effective. This new number matches Moderna's reported effectiveness reported yesterday. I don't know enough about how the reporting process works. To me, it appears that Pfizer will report whatever number sounds good, not the true number. I'm glad several states, like New York, want to review the clinical trial data independently of the FDA

EDIT: I am getting serious downvotes for this comment! Whoops! I do not mean to suggest people should not take the vaccine, only that the optics of news presses look bad. I say this as someone who takes the Flu vaccine every year and elected for the HPV vaccine a few years ago

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The 95% effectiveness value is based on the risk ratio: https://sphweb.bumc.bu.edu/otlt/mph-modules/ep/ep713_associa...

From this comment, which summarized the statistics of the phase 3 trial: https://news.ycombinator.com/item?id=25136588

- The percentage of people in control that had confirmed COVID-19 cases was ~0.79%

- The percentage of people in treatment that had confirmed COVID-19 cases was ~0.04%

- This represents a risk ratio of 0.04/0.79 = ~0.05.

A risk ratio of 1.0 means that there was no reduction in risk, i.e. the treatment had no effect. A risk ratio less than 1.0 means that the treatment reduced the risk (or was correlated with this), and above 1.0 means that the treatment increased the risk (or was correlated with this).

Since the risk ratio of treatment was 0.05, there was a 0.95 reduction in risk, which is where the 95% number comes from.

Didn't they initially announce effectiveness as people infected in the trial arm over people infected in the control arm? Changing the metric to the better one feels a bit marketingy.

Pfizer's Phase 3 study was meant to have three readouts of data, which would happen when they hit a pre-specified number of cases. The first readout was to have been at 32 cases in design, but after discussion with the FDA, Pfizer changed the first readout to 62 cases. By the time the discussion concluded, the study had already hit the second readout of 94. The final study analysis is concluded at 164.

The 90% efficacy is reported based on the second readout data, which was all the data they had at the time. The 95% efficacy is reported based on the final readout data, which was only more recently available.

Note that the media has not done a great job of indicating that the initial Pfizer (and Moderna, for that matter) results were based on interim analysis.

“I don’t know enough about the reporting process” yet continues to come up with a theory based on nothing.

I added that sentence to make it clear that I am not an expert. I am highlighting how this appears to me. I was hoping that someone with experience working in clinical trials would chime in

You can follow Dr Eric Topol or Dr Florian Krammer on twitter as they for sure will be able to explain the data in layman terms. Great people to follow. There are others as well.

Yet by publicly speculating about unethical behavior that you have no basis for, you give wrong and potentially harmful ideas to people who are not experts. If you want to get an expert opinion, you should ask "Why did the effectiveness rise from 90% to 95%?".

For much the same reasons as you don't want people adding additional baseless speculation to passing observations of you that you may be a pedophile in passing conversation.

If that was indeed your intent, it definitely didn't sound like that in your post, which came across as unwarranted conspiracy theory BS.

You could have gotten your point across better without insinuating negative intent, i.e. "As someone unfamiliar with the reporting process, can someone more familiar with the process explain how Pfizer's effectiveness number went from 90% just recently to 95% today? Thanks in advance."

If you're looking to be educated, instead of drawing unfounded conclusions, you might instead ask a question, like "I'm confused what these numbers represent. Could someone more versed in clinical trials explain them?"

This comes across much differently than "this seems like these numbers -- which I confess I do not understand -- seem manufactured by the drug companies to look good."

> come up with a theory based on nothing

Not a crime, but strictly speaking, thats how theories are formed. You test them or otherwise find evidence that contradicts them.

You're thinking of hypothesis. https://www.merriam-webster.com/dictionary/hypothesis#note-1 Hypo- meaning "lower" or "lesser".

Oops, you are correct.

They got more data so they updated the number to 95%, if a member of the public doesn't understand that they are just being willfully ignorant.

How much more data did they get? For a trial that's been going on for months, it seems nonintuitive that 2 more days of data would move the needle so much

Well with case counts in the US doubling roughly every two weeks, you would expect to see the number of cases among trial participants there doubling over that period.

There are two differences between the 90% reported originally and the 95% now. The first value was a lower bound, it was formulated a bit mushy as far as I remember, but it almost certainly wasn't the same type of value as the one reported now. And the trial is now finished, the first value was from an interim analysis with fewer data points. So there is nothing unusual here at all.

> I just read that Pfizer reports its vaccine as 95% effective, even though pharmaceutical originally reported its vaccine as 90% effective

I think, "originally" is not the right term. "Pfizer’s Early Data Shows Vaccine Is More Than 90% Effective".

Now more data is in, and it is indeed more than 90% effective, more like 95%.

They already have sold the vaccine, and it won't be sold over the counter. I don't see any gain in telling to have 93%, 95% or 98% efficacy, if you don't have it.

Yep. I've immediately read that "we're evaluating whether the second dose would increase it to around 94-95%", I guess they did.

The Pfizer press release reported a week (or so) ago said the vaccine was "over 90% effective" in the preliminary data. They did not explicitly say the vaccine was 90.000% effective.

Clinical trials like this are subject to an enormous number of regulatory and statistical controls, particularly if they're in the public spotlight as much as this one is. It's unlikely the true effectiveness of the vaccine will be very different from what they're reporting here.

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