Are you safe from COVID-19 if you’ve had the common cold?
The case for cross-immunity
For epidemiologists, the evidence of waning immunity and cross-immunity didn’t come as a surprise.A study from 1990showed that soldiers infected with one of the milder coronaviruses didn’t retain immunity for much longer than a year. Also, the boom-bust cycle that the milder coronaviruses undergo from year to yearcan be explainedby a mix of waning immunity and cross-immunity.
The milder coronaviruses can generate similar antibodies to the ones that are generated by the coronaviruses thatcause Sars and Mers. These antibodies are so similar that theynearly trickeda British Columbia care facility into thinking they had an outbreak of Sars after the Sars epidemic had been declared over. In fact, the outbreak was caused by OC43, one of the coronaviruses that causes the common cold.
Nevertheless, infections that generate structurally similar antibodies don’t necessarily provide cross-protection in a medically meaningful way.
We’re still just not sure
Evidence for cross-protection between all but the most closely related coronaviruses is scant.
It is difficult to say whether the milder coronaviruses protect against SARS-CoV-2 partly because we have done so little surveillance on them. Ideally, we would be able to look at historical data to identify which communities experienced major outbreaks of each milder coronavirus strain over the past few years and then see if there is a link with less severe COVID-19 cases.
Challenge studies, in which a person is intentionally infected with a milder coronavirus strain and then exposed to SARS-CoV-2, could also address the question but are dangerous and ethically fraught. For now, all we can say is that the possibility that the common coronaviruses might protect against SARS-CoV-2 remains just that – a possibility. Indeed, Mateus and colleagues describe this theory as “highly speculative.”
This article is republished fromThe ConversationbyStephen Kissler, Postdoctoral Researcher, Immunology and Infectious Diseases,University of Cambridgeunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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