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Wes Pegden Profile picture
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16 Dec, 4 tweets, 2 min read
The fast pace of recent decisions surrounding the use of boosters shots in low-risk populations comes amid a backdrop of significant expert dissent, and has been facilitated, in part, by bypassing scientific advisory committees.

1/
washingtonpost.com/outlook/2021/1…
It is surprising that against this backdrop, some universities (including, just today, @CarnegieMellon) have announced booster mandates for students, whose age make the risk/benefit calculation of boosters especially questionable, in part b/c of myocarditis events.

2/
I hope university administrators realize that with these policies, they are *requiring* students adopt a pharmaceutical intervention that domain experts do not even all agree should be *recommended* in this population.

3/3
nymag.com/intelligencer/…
These booster mandates for 18-22 year olds will proceed as ~half of vaccinated nursing home residents still haven't received booster shots.

Booster policy is just one more case where we have lost the plot with respect to thoughtful management of risk.
4/3

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More from @WesPegden

Wes Pegden Profile picture
3 Dec
Quick thread about re-randomization in randomized trials, illustrating the following two simple points:
*) re-randomization for balance is sometimes fine and doesn't affect significance thresholds
*) re-randomization for balance can sometimes cause big artifacts.

1/14
First scenario, consider a clinical trial, where we randomize individuals independently (by individual coin flip, say) to treatment or control groups.

What if we re-randomize until the two groups have exactly the same size?
2/14
This is the same as choosing an equal split uniformly randomly, and standard statistical approaches will still apply without problems.

It is similar if one re-randomized until the populations were within some threshold, or if this was true for subgroups (sex, race, etc).
3/14
Read 14 tweets
Wes Pegden Profile picture
2 Dec
This blog post discusses our re-analysis of the recently released data from the Bangladesh mask trial (with @ChikinaLab and @beenwrekt).

An accompanying short note is linked from the blog (arXiv link later).

Thread what we find: 1/
We carried out simple analyses of this data using standard nonparametric paired statistical tests.

Through this lens, there are highly significant effects on behavior, but the primary outcome (symptomatic seropositivity) is not significant. 2/..
One of the striking things in the figure above is the imbalance in the size of the consenting populations between the (50:50 randomized) treatment/control groups. There are highly nonrandom differences in the rates consent staff reached households in treatment/control villages.
Read 11 tweets
Wes Pegden Profile picture
27 Sep
The authors of this study are doubling down on @Jabaluck's "guesstimate" of the # of lives masks would save in the U.S. based on their (impressive, sorely needed) cluster trial in Bangladesh.

There are many reasons this guess is speculative to the point of not being useful.
1/6
Apart from the obvious things about translating a finding which was highly context specific (the benefit concentrated in particular ages and in villages using a particular mask type) to a completely different context, one cannot make these estimates ignoring epidemic dyanmics. 2/
E.g.:
Suppose every K infections results in death.

To a first approximation, to believe "masks for a year" prevents x deaths, you either have to believe that it increases by K*x the number of people who will never get infected, or the number who would get vaccinated first.
3/
Read 6 tweets
Wes Pegden Profile picture
1 Sep
Everyone should look at the remarkable work done in this cluster randomized trial.

They found that an intervention which increased surgical mask uptake in community settings significantly reduced SARS-CoV-2 infection among older adults.

A thread.
1/6
Most people's 1st tendency is to claim studies like this support what they already knew. In reality, the study had specific and not necessarily intuitive findings.

The study even collected predictions from experts, and found that they failed to predict the study outcomes!
2/6
For example, the study found that increasing mask usage had statistically significant effect on SARS-CoV-2 infection.

But these results were driven by surgical mask use, and by reductions in infections in people over 50.

A brief reminder that CDC mask guidelines start at age 2.
Read 9 tweets
Wes Pegden Profile picture
31 Aug
On Friday, epi-Twitter exploded with urgent discussion of an MMWR on an isolated incident in which 1 teacher infected an unusual number of students.

Receiving much less attention was an MMWR on the same day of lower case rates all last year in LA schools than in the community.1/
At the time of this writing, the MMWR with data had 74 retweets and the MMWR on that one time this one crazy thing happened had 1.1K retweets, many from serious people claiming that this report affected in some fundamental way our understanding of COVID-19 risk in schools.
2/
Data is boring and stories seem compelling. But scientists and public health agencies should be actively working against the natural tendency to give greater weight to outlier incidents than data-driven understanding of risks.
3/
Read 4 tweets
Wes Pegden Profile picture
31 Aug
One idea that has not been discussed much is the question of whether regulators have a special role to play in deciding when coercive measures can be used to increase uptake of vaccines.

In practice the hurdle for this has just been EUA, not even full approval.
1/
I think it is worth thinking about what principles should guide the decision of when coercive measures are ethically appropriate and whether regulators should play a role in adjudicating when that bar is crossed.

2/
The current situation is that we allow mandates even in cases where no clinical trial has weighed the direct individual risk/benefit (e.g., mandates for individuals with confirmed previous infection. This may also be the case soon for boosters).

This certainly seems flawed.

3/
Read 4 tweets

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