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The Centers for Disease Control and Prevention (CDC) on Jan. 13 published this statement on its website: “CDC & FDA Identify Preliminary COVID-19 Vaccine Safety Signal for Persons Aged 65 Years and Older.”

The signal was identified through Vaccine Safety Datalink (VSD), “a collaborative project between CDC’s Immunization Safety Office, integrated health care organizations, and networks across the U.S.,” that “uses electronic health data from participating sites to monitor and assess the safety of vaccines.”

The CDC and U.S. Food and Drug Administration analysis of VSD data found:

  • There was an increased risk of ischemic stroke in bivalent booster recipients ages 65 and older.
  • The risk was present in the Pfizer formulation but not in Moderna’s.
  • The signal was raised because of increased stroke risk in the 21 days following inoculation compared to the risk on days 22-42.
  • The signal did not change the CDC’s recommendations for either bivalent boosters (Pfizer or Moderna).

Let’s break this down …

VSD raw data is not readily available to the public, so key questions remain around the significance of the signal and the criteria being used to prompt further investigation.

The CDC bulletin indicates that the risk of stroke is higher immediately after getting a Pfizer bivalent booster. But how much higher? The CDC doesn’t tell us.

Moreover, the CDC’s concern is around the increased stroke risk in the first three weeks compared to the risk in the second three weeks. But what is the absolute risk? In other words, how does the risk of stroke in boosted individuals compare to those who are not boosted?

The CDC does not tell us that, either.

The omission reveals something peculiar about the criteria that triggers a “safety signal” in the eyes of our public health agencies. If the risk of stroke was just as high on days 22-42 as on days 1-21, would a safety signal occur? Apparently not.

Why didn’t the Moderna formulation trigger a safety signal too? Was it because the risk of stroke was lower than in Pfizer’s — or because the risk was equally high in the first three weeks as the second three weeks?

As explained, it would seem to be the latter.

CDC offers assurances using irrelevant or contradictory data

Nevertheless, the CDC puts all of these questions to rest:

“CDC continues to recommend that everyone ages 6 months of age and older stay up-to-date with COVID-19 vaccination.”

They support this recommendation by citing four different data sources.

The first purportedly shows that “an updated COVID-19 vaccine reduces the risk of hospitalization from COVID-19 by nearly 3-fold compared to those who were previously vaccinated but have not yet received the updated vaccine.”

The data is from a CDC Morbidity and Mortality Weekly Report published Dec. 30, 2022, that examines risk of COVID-19 hospitalizations AND urgent care visits in adults 18 and older. The report does not provide bivalent booster efficacy for the age group of concern, 65 and older.

Without knowing the risk of ischemic stroke, it is impossible to determine whether the benefit of the booster is worth the risk. Beyond that, is it reasonable to equate an urgent care visit for COVID-19 with an ischemic stroke? That is debatable.

The second data source is from the CDC’s “COVID Data Tracker” which indicates that the risk of COVID-19 death is 18 times lower if fully vaccinated and bivalently boosted compared to unvaccinated. However, this number is for the month of October 2022 only, applies to all individuals age 5 and older and entirely misses the point.

The bivalent booster is not given to the unvaccinated, only those who have received the primary series are eligible. How does this help someone decide if they should get the booster or not? It doesn’t.

In any case, we can use the COVID Data Tracker to calculate the benefit of the bivalent booster when given to fully vaccinated individuals. For the month of October, the bivalent booster, when given to individuals ages 65 to 79, prevented between 1.6 to 5.9 weekly deaths for every million doses given.

In other words, 170,000-620,500 boosters are required to prevent a single COVID-19 death per week. How many ischemic strokes will result from more than a half million bivalent booster doses? The CDC doesn’t tell us.

The third data source is from a preprint study (not peer-reviewed) in the Lancet. The CDC accurately states the study’s key finding, that bivalent boosters reduce the risk of COVID-19 hospitalization by 80% in people over 65.

What is not mentioned is that the risk of COVID-19 hospitalization (as determined by the study’s authors) during the 70-day period of observation is 0.055%, or 1 in 1,818. The booster offered a 0.048% risk reduction in hospitalization.

Once again, because the CDC doesn’t tell us what the risk of ischemic stroke is — only that it is “increased” — it is impossible to draw any conclusions about risk vs. benefit from this study either.

Finally, the bulletin cites this weekly report from Nov. 4, 2022, which summarizes the purported safety of the bivalent booster in individuals ages 12 and up from Aug. 31-Oct. 23 using the Vaccine Adverse Event Reporting System, or VAERS, and V-Safe databases.

Here’s what it reported:

  • 0.8% (1 in 125) of booster recipients reported seeking medical care after inoculation (V-Safe).
  • 4.5% (1 in 23) of the 5,542 adverse events associated with the bivalent booster that were reported in VAERS were serious.

How does the CDC summarize all of these findings?

“Staying up-to-date with vaccines is the most effective tool we have for reducing death, hospitalization, and severe disease from COVID-19, as has now been demonstrated in multiple studies conducted in the United States and other countries.”