Even after three COVID-19 vaccine doses, high blood pressure more than doubles the risk for hospitalization with an omicron variant infection.

That’s according to a new study of 912 patients from Cedars-Sinai Medical Center. The researchers analyzed healthsystem data for patients who became infected after receiving three shots. Of the participants, 145 — or nearly 16% — were hospitalized with COVID-19.

High blood pressure stood out as the most significant factor in hospitalization risk, reported Joseph Ebinger, MD, and colleagues. This was true even without the presence of other major chronic diseases such as kidney disease or heart failure, they found. 

“The people who are most at risk are not necessarily who we think they are,” Ebinger said in a statement. “They are not the sickest of the sick, and this was a surprising finding.”

The use of drugs for controlling blood pressure, including ACE inhibitors and/or angiotensin receptor blockers, had no impact on the results, they added.

Additional factors that elevated the risk of hospitalization after a third COVID-19 vaccination included older age, cardiovascular disease, heart attack or heart failure. A longer duration between the last vaccination and infection also was tied to higher risk.

“These findings are important since about half of the adults in the U.S. have high blood pressure,” Ebinger said in a statement. “We need to raise awareness and understanding that receiving three doses of a vaccine may not prevent severe COVID-19 in everyone, especially among people with high blood pressure.”

COVID-19 vaccines helped to curtail severe illness early in the pandemic, and receipt of a first booster shot (third mRNA vaccination) has reduced hospitalization risk by 90% during the omicron period, according to the Centers for Disease Control and Prevention. However, some fully vaccinated and boosted people still experience poor outcomes.

Full findings were published in the journal Hypertension.

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