People who have been exposed to a seasonal “common cold” may experience less severe COVID-19 symptoms.
While we’ve discussed this topic previously, a study from the Journal of Clinical Investigation reports the first clinical evidence of cross reactivity with the common cold and COVID. This is due to previous immune responses against the four endemic coronaviruses that cause the common cold and pneumonia.
The clinical findings are based on reviewing PCR tests from nearly 16,000 patients at the Boston Medical Center between 2015 and 2020. 875 of these patients tested positive for an endemic coronavirus and over 15,000 patients never showed a documented coronavirus infection. About 11% or 1,800 patients returned between March and June 2020 for the SARS-CoV-2 test. After comparing between test results between those with known endemic coronavirus infections and those without infection, the authors concluded that recent infection with the endemic coronaviruses didn’t keep patients from being infected with COVID-19, but that COVID-19 is much less severe in patients with the previous endemic infection. Specifically, 4.8% of hospitalized patients with previous endemic coronavirus infections died compared to 17.7% of those in the group without previous infection. Also, the odds of ICU care were significantly lower in those with previous endemic infections (OR 0.1).
Along the same line, mothers who have been infected with COVID-19 may be passing viral immunity to their babies through antibodies in breastmilk. A small study published in iScience of 15 women found that the mother’s breastmilk contained COVID-19-reactive secretory immunoglobulins and may be a potential therapeutic option for severe COVID-19, however the authors note that more research is needed.