A history of pneumonia is the second-greatest overall risk factor for death from COVID-19, Harvard University researchers said.

A prior episode of pneumonia was the second-greatest overall risk factor for death from Covid-19, according to a study of medical records from almost 17,000 patients. The top predictor of risk is age, with the risk increasing as people get older.

By itself, a single pneumonia case probably doesn’t put someone at high risk, the researchers cautioned. Rather, it’s more likely an indicator of underlying chronic disease — such as chronic obstructive pulmonary disease or interstitial lung disease — that’s gone undiagnosed, they said.

Health officials have broadly prioritized older people and health workers to be first in line for potentially life-saving Covid vaccines, because of their risk of death and exposure to the disease. A machine-learning analysis of mortality patterns can help pinpoint others at high risk and alert doctors, officials and patients to respond, according to the study’s leader, Hossein Estiri, an assistant professor at the Harvard-affiliated Massachusetts General Hospital’s Laboratory of Computer Science.

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