Seasonal coronavirus antibodies correlate with lower COVID-19 severity Patients critically ill with COVID-19 infections had significantly lower levels of antibodies against seasonal human coronaviruses (HCoVs) OV43 and HKU1 than those with mild to severe infections, according to a German study published yesterday in the International Journal of Infectious Diseases. The researchers say the results could indicate that prior infections from seasonal coronaviruses, which frequently present as mild pediatric respiratory tract infections, may help prevent severe COVID-19 illness. University Hospital of Munster researchers drew serum samples from 60 people with confirmed COVID-19 infections. Participants included outpatients (41.7%), hospitalized patients with severe or moderate disease (26.7%), and hospitalized patients with critical disease (31.7%). Outpatients were selected to match inpatient sex and age as best as possible. The median age of outpatients and those with critical illness was 58 and 55 for inpatients with severe or moderate illness.