The United States Centers for Disease Control and Prevention (CDC) is investigating a potential link between the Bivalent Pfizer-BioNTech COVID-19 vaccine and an increased risk of ischemic stroke in people aged 65 and above.

The health agency said a preliminary COVID-19 vaccine (safety signal) had been identified and promptly ordered an investigation. The CDC also released a statement on Friday saying that the initial call was not identified with the Bivalent Moderna COVID-19 vaccine.

Risk of Ischemic Stroke

Authorities said that following the availability and use of the updated COVID-19 vaccines, the agency's Vaccine Safety Datalink (VSD), a near real-time surveillance system, has met the statistical criteria to warrant further investigation. This was to determine whether or not there was a safety concern for ischemic stroke in the above age group for those who received the Pfizer-BioNTech COVID-19 vaccine.

CDC officials added that a question was raised following the rapid-response investigation if people 65 and older who received Pfizer's vaccine were more likely to develop ischemic stroke 21 days after completion of their shots, as per Fox News.

The health agency also stated that an extensive study of updated bivalent vaccines from Pfizer-BioNTech found no increased risk of ischemic stroke when using the Centers for Medicare and Medicaid Service database.

Furthermore, the CDC said that the Vaccine Adverse Event Reporting System (VAERS), managed by the health agency and FDA, has not seen an increase in reporting of ischemic strokes following the updated (bivalent) vaccine.

A Pfizer spokesperson, in a statement, said that Pfizer and BioNTech were made aware of the limited reports of ischemic stroke observed in people aged 65 and older following vaccination with the Omicron BA.4/BA.5-adapted bivalent COVID-19 vaccine.

Read Also: COVID-19 Autopsies Reveal Stunning Information 

Pfizer-BioNTech's COVID-19 Vaccine

The health agency's statement also noted that while the totality of the data suggested that there was a low likelihood that the signal presented a real clinical risk, they deemed that it was necessary to share such information and findings with the public, similar to what they have done in the past, according to Politico.

Ischemic stroke is a condition that occurs when a blood clot blocks the arteries pumping blood to a person's brain. Pfizer and BioNTech said there was no evidence to conclude that the condition was associated with the companies' COVID-19 vaccines.

Furthermore, the companies' announcement prompted a response from House Energy and Commerce Chair Cathy McMorris Rodgers of Washington. The Republican lawmaker said the CDC and FDA would need to testify before her committee regarding the situation.

The two government agencies concluded that there was no need to change the recommendation that everyone aged six months and older should be up to date with their COVID-19 vaccinations. This includes those aged five and older who are eligible for the updated booster.

The findings resulted from government vaccine safety experts combing through databases containing millions of records in the US. They also consulted with regulators in other countries but have not found indications that the statistical signal represents a clinical risk to patients, said the Washington Post.

Related Article: US Vaccination Rates Drop for Measles