A recent post on Facebook shared a screenshot of an article claiming that receiving the Pfizer COVID-19 booster vaccine and flu vaccine on the same day may increase one’s risk of stroke.
The article referred to in the Facebook post was published on MailOnline, the online version of the British tabloid, The Daily Mail.
According to the article, the United States Food and Drug Administration (FDA) has preliminarily found that receiving both the flu vaccine and Pfizer’s COVID-19 bivalent booster on the same day might increase the risk of stroke among those above the age of 65.
Safety of vaccines
The United States Centers for Disease Control and Prevention (CDC) works with participating healthcare organisations and networks to track how safe vaccines are and conduct studies of the uncommon and serious adverse events following vaccinations. This is done through a project called Vaccine Safety Datalink (VSD).
Since its inception in 1990, the VSD has assessed the safety of multiple vaccines such as the rotavirus vaccine, and recently the COVID-19 vaccines.
The VSD uses electronic health data from its partners, such as information on the type of vaccine given to a patient, whether more than 1 vaccination was given on the same day, and whether there were any related emergency department visits, to track and evaluate the safety of vaccines. Using the data collected, the VSD determines if there have been detrimental results from the vaccine.
Concern(s) about the Pfizer-BioNtech bivalent COVID-19 booster
During this routine data collection, the VSD detected a possibility that those aged 65 and above who received the Pfizer vaccine could be at risk of having an ischemic stroke. This prompted further investigations by CDC and FDA.
Subsequent studies by the CDC and FDA did not find a generally increased risk of ischemic stroke following the receipt of the bivalent vaccine.
VSD examined the data of those aged 65 and above who suffered an ischemic stroke following the Pfizer bivalent COVID-19 booster and found that in a subset (of 22 patients who suffered an ischemic stroke 11-21 days after their booster), 14 patients (64%) had also received the flu vaccine on the same day.
Hence, some seniors aged 65 and above did suffer an ischemic stroke after receiving both the Pfizer bivalent booster and flu vaccine on the same day.
However, the data collected is not conclusive that receiving the Pfizer bivalent booster and flu vaccine on the same day may lead to an increased risk of an ischemic stroke for those who are 65 or older.
As this is only an initial study, both the CDC and FDA are conducting further studies on the risks of administering the flu and COVID-19 bivalent booster vaccines on the same day.
Can the flu and COVID-19 booster vaccines be administered at the same time?
Presently, the CDC has not advised against receiving the flu and COVID-19 booster vaccines simultaneously if both are due, since it is a common medical practice to allow one to be up to date on all required vaccines.
Locally, according to Singapore’s Ministry of Health, an interval of 14 days is recommended between a COVID-19 and non-COVID-19 vaccine although persons above the age of 5 can still proceed with receiving a non-COVID-19 vaccination, within 14 days of the COVID-19 vaccination.
Overall, it is inconclusive whether receiving the Pfizer bivalent COVID-19 booster and flu vaccine will lead to a risk of ischemic stroke, especially among those above the age of 65, and further studies are required to verify the claim.