The latest report by the FDA has stirred up another wave of anti-vax misinformation online…
Tweets, and posts on Facebook and Instagram claiming that the ‘FDA now says Pfizer causes blood clots,’ clocked up thousands of hits during the Christmas holidays, with chief Twit Elon Musk adding his two cents on 18 December 2022, claiming that ‘Much will come to light as Fauci loses power.’
Yet the actual conclusions drawn by the authors of the report allude nothing of the sort.
The original study, Surveillance of COVID-19 vaccine safety among elderly persons aged 65 years and older, published 1 December 2022 by Elsevier, evaluated 14 outcomes of interest using vaccination data from the US Centres for Medicare & Medicaid Services (CMS) data covering almost 31 million older Americans.
The study compared outcomes for more than 17 million doses of Pfizer’s BioNTech, over 16 million doses of Moderna and some 630,000 vaccinations using Janssen’s formula (administered between 11 December 2020 and 15 January 2022), across four groups – and significantly, it was the comparisons between these cohorts that caused the allegations of a blood-clot cover-up to resurface.
The first group of over-65s included in the study comprised those administered one of the three vaccines, with weekly vaccine uptake registered by brand.
The second was a historical control group representing pre-COVID levels of risk, and the third contained data collected from 1 January 2020 to 10 December 2020 – defined by the authors as the peri-COVID period – which enabled comparisons between those who had contracted COVID vs those who had only received the vaccine.
The fourth and final cohort was comprised of older Americans who had been vaccinated against the flu, to try and capture the differences between those who actively sought out health-related interventions, and those either unwilling or unable to engage with additional services – an important driver of total health outcomes in the highly privatised and outrageously expensive US market.
Out of the 14 outcomes of interested evaluated, only four met the threshold for a statistical signal after vaccination with Pfizer’s BNT162b2 when compared to the historical control group: pulmonary embolism (PE; RR = 1.54), acute myocardial infarction (AMI; RR = 1.42), disseminated intravascular coagulation (DIC; RR = 1.91), and immune thrombocytopenia (ITP; RR = 1.44).
However, once the data for Pfizer was evaluated to allow for the impact of confounding factors, only pulmonary embolism still met the statistical threshold for a signal.
“The statistical signals of four serious outcomes are not necessarily causal and may be due to factors potentially unrelated to vaccination,” the authors said.
“Because an early warning system does not prove that the vaccines cause these outcomes, more robust epidemiologic studies with adjustment for confounding, including age and nursing home residency, are underway to further evaluate these signals.
“Additional analyses indicated that the potential association was less than twice the historical rates and may be associated with factors not accounted for in the near real-time surveillance methods.
“For example, the elderly Medicare population that received the BNT162b2 vaccine differed from other elderly COVID vaccinated populations, including a preponderance of nursing home residents and populations with a higher comorbidity burden.”
The real purpose of the study was to evaluate the effectiveness of the FDA-CMS near real-time active surveillance program, which rapidly detects safety concerns that may not have been voluntarily reported to passive surveillance initiatives such as the Vaccine Adverse Event Reporting System.
Routinely used by FDA in safety surveillance for annual flu vaccines over the past decade, this method is designed to be sensitive enough to quickly screen safety signals for further evaluation in robust epidemiologic studies.
And according to the authors, the ability to detect and evaluate the weak signal strength detected by the system in their study effectively demonstrated the validity of the early warning surveillance program.