Younger patients (under age 65) who suffered severe symptoms had a particularly high mortality risk at 3.3 times as likely to die as patients under age 65 who tested negative.

'We conducted a previous study that showed that patients with severe Covid who recovered were at significantly greater risk of being hospitalized in the subsequent six months,' said Dr Arch Mainous, lead author on the study, in a statement.

Overall, mortality risk was 'significantly higher' for the patients with severe Covid compared to those with mild cases or no infection, the researchers found.

Patients with severe Covid were 2.5 times as likely to die within 12 months of their diagnoses compared to those who didn't test positive.

Severe Covid patients were also 1.9 times as likely to die within 12 months as those who had mild Covid.

These patients were 3.3 times as likely to die within 12 months of their diagnoses as Covid-negative patients under age 65, and 2.8 times as likely to die as mild Covid patients in the age group

Meanwhile, severe Covid patients over age 65 were 2.2 times as likely to die within 12 months as Covid-negative patients over age 65, and 1.4 times as likely to die as seniors with mild Covid

'Since we now know that there is a substantial risk of dying from what would likely be considered to be an unrecognized complication of Covid, we need to be even more vigilant in decreasing severe episodes of Covid,' Mainous said

Numerous studies have shown that vaccination decreases patients' risk of severe Covid symptoms, hospitalization, and long Covid