Thread by @DoctorYazanA

ALWAYS refer to the original data source. Beware of misleading headlines. 🧵

A study by FDA’s Hui-Lee Wong et al is being referenced all over Twitter as:
“FDA now says Pfizer vaccine causes blood clots”.

This conclusion is inaccurate.
(Cont’d)
cc: @elonmusk

https://twitter.com/hodgetwins/status/1604247306034978818

Here’s the link to the original paper: doi.org/10.1016/j.vacc…

The authors used Medicare/Medicaid data to analyze 14 different adverse outcomes after 34 million vaccine doses in recipients age >65. The controls used for comparison were HISTORIC controls, pre-COVID & peri-COVID.

When compared to the PRE-COVID population (2017-2019), #pulmonaryembolism met modest statistical significance (RR=1.48), the difference was lost when the peri-COVID (2020) comparator population was used instead. The difference remained when inpatient setting was used.

This data cannot be used to claim causality. The authors agree. Why?
1️⃣Not controlled for underlying comorbidities (only age, sex, race, nursing home residency)
2️⃣The control group was from a different time period
3️⃣Database studies prone to inaccuracies
4️⃣Correlation≠causation

It is well-known that such limitations are notoriously common in database studies that use historical controls, which is why they are not a standard in evaluating safety/efficacy. Correlations are to be taken with a grain of salt.

So it is wrong to say “causes”, when this was a modest correlation, that disappeared with a different control group, and could not be controlled for significant medical factors that can cause blood clots. This was also specifically for age >65 and not rest of population age.

Also wrong to imply this is some big “secret that the FDA was hiding and just announced”. The study was completed now, and its publication reflects transparency. Meanwhile, many other large studies on mRNA vaccines (clinical & laboratory) did not find a correlation even.