(The Hill) — A study published on Thursday found that pregnancy nearly doubles the risk of breakthrough COVID-19 cases, closely followed in risk by a solid organ transplant.

The study conducted by Wisconsin-based company Epic found that among the comorbidities that increase the risk of a breakthrough COVID-19 infection, pregnancy increased this risk the most by 1.91 times, which analyzed data from over 140 million patients from 161 of the company’s organizations. 

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Individuals were 1.83 times more likely to have a breakthrough COVID-19 infection if they had a solid organ transplant; those with an immune system deficiency were 1.63 times more at risk, according to the study.

Other comorbidities that increased the risk of a breakthrough infection, though to a lesser degree, included those who had kidney disease, liver disease or mental health issues, among others.

“… we did not find that cancer or Down syndrome increased the risk of breakthrough infection. This is consistent with other research on the rates of COVID-19 in populations with cancer versus populations without,” the study said. 

“These findings support the CDC’s recommendation that patients with a high-risk comorbidity may need to use enhanced infection prevention control beyond vaccination to minimize the risk of a COVID-19 breakthrough infection.”

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The development comes more than two years since the World Health Organization (WHO) declared the coronavirus a pandemic.