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Partially vaccinated or unvaccinated COVID-19 patients in California were at significantly higher risk for related non-respiratory consequences such as fever and abnormally rapid heart rate, as well as death in certain variant periods, a team led by University of California (UC) Irvine researchers reports in Vaccine.
The team conducted a longitudinal retrospective review of the electronic medical records of 63,454 UC COVID-19 patients of any age or hospitalization status to determine rates of non-respiratory symptoms, vaccination status, and death by 30 days after diagnosis by variant period from January 2020 to April 2022. The study period spanned the predominance of the wild-type, Alpha, Delta, and Omicron variants; vaccines were available to most people starting in the Delta wave.
Full vaccination was considered the receipt of at least two COVID-19 vaccine doses. Of all patients, 12.3% were fully vaccinated, and 87.6% had received one or no dose.
Vaccine protected against death even in younger people
Rates of fever, the most common symptom across all variant periods, were significantly higher among partially vaccinated or unvaccinated than in fully vaccinated patients during the Delta and Omicron waves.
Cardiac conditions were significantly more common in those not fully vaccinated amid Omicron, and tachycardia (abnormally rapid heart rate) occurred only in this group during Delta and Omicron. High blood pressure was the most common cardiac feature, regardless of variant period or vaccination status.
Our findings reveal distinct features of each wave and a significant association of most features with vaccination status.
Partially vaccinated and unvaccinated patients were at significantly higher risk for death in the Delta and Omicron periods (Delta odds ratio [OR], 1.64); Omicron OR, 1.96). Diabetes and gastrointestinal reflux disease were reported during all variant periods, regardless of vaccination status.
"Our findings reveal distinct features of each wave and a significant association of most features with vaccination status," the researchers wrote. "Although Omicron was shown to affect mostly younger people, the risk of death was still higher in the unvaccinated population, and thus the vaccine provided some protection from COVID-19 even among younger individuals."