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We Now Know What A Healthy Immune Response To COVID-19 Looks Like

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Stephen Luntz

Freelance Writer

clockMar 18 2020, 10:35 UTC
covid blood

Samples of blood taken from a COVID-19 infected patient reveal how her immune system responded, leading her to get better starting three days after antibodies appeared. MAMIAE T8/Shutterstock

Medical scientists have described the immune response of someone with mild-to-moderate COVID-19 infections who beat the disease fairly quickly. Their observations could help fight the virus in several ways, particularly identifying those most in need of scarce medical resources.

Most attention in a pandemic focuses on the sickest individuals, but researchers at Australia's Doherty Institute were keen to observe how the immune system responds in the majority of cases. When an otherwise healthy 47-year-old woman presented to a Melbourne hospital with a case severe enough she required admission, but without apparent threat to life, they were ready. With permission, blood samples were taken daily, along with detailed notes of her progression and vital signs.

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“We looked at the whole breadth of the immune response in this patient using the knowledge we have built over many years of looking at immune responses in patients hospitalised with influenza,” Dr Oanh Nguyen said in a statement

Although the obstinate band of people claiming COVID-19 is “just the flu” are very wrong, the Doherty team did see a lot of similarities to an immune response to common flu strains.

“Three days after the patient was admitted, we saw large populations of several immune cells, which are often a tell-tale sign of recovery during seasonal influenza infection, so we predicted that the patient would recover in three days, which is what happened,” Nguyen said.

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The patient's immune system treated the virus as similar to influenza and released similar antibodies. By seven days after admission the woman no longer tested positive for COVID-19 and by day 13 the last of her symptoms were gone, although her antibodies continued to rise thereafter.

The work is published in Nature Medicine. Subsequent, as yet unpublished, studies of four other patients with similar symptom severity showed similar responses.

Researchers now have a better idea of the reaction they hope a vaccine will induce. With so many vaccines under development, the Doherty Institute's work will also make it easier to identify those which produce the best reactions and should be prioritized.

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More urgently, the work gives doctors a better idea of which patients are likely to recover of their own accord several days before progress can be seen in their symptoms. This will allow them to focus their efforts on those whose immune response looks different, putting them in greater danger.

Normally research like this would be delayed by the need to develop a strategy and gain ethics clearance, but the Institute has been preparing for an epidemic for years. It established Sentinel Travellers and Research Preparedness for Emerging Infectious Disease (SETREP-ID), a system for collecting samples from carriers of new infectious diseases, with as much pre-work done as possible in the absence of knowing the coming threat.

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Colds, Flus, and the Coronavirus are all different, and their symptoms don't perfectly align but the immune system can deploy quite similar responses.


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