Hence, the duration of immunity to a new coronavirus like SARS-CoV-2 is very difficult to know. We will just have to ‘wait and see' -- which is an expression that I find myself using so often with COVID19 and that is so frustrating for all of us. 21/
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But we already can know, and do know, the *early* time course of immunity for COVID19, over the first 40 days since onset of illness. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3546052 … via
@TheLancet 22/3 antwoorden 185 retweets 1.144 vind-ik-leuksDeze collectie tonen -
“Seroconversion" in 173 patients appeared for Ab, IgM, & IgG in 11, 12, & 14 days. Presence of antibodies was <40% in first 7d & then rapidly increased to 100%, 94%, & 80% for Ab, IgM, & IgG by 15d. In contrast, viral RNA decreased from 67% before day 7 to 46% in days 15-39. 23/pic.twitter.com/rHAQEYmiSI
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We can, however, look at other coronaviruses and see what we can learn about the possible duration of immunity for COVID19, once we are further into the epidemic and have longer follow-up. We can guess based on past science. 24/
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Here is a classic 1990 study of 15 volunteers who were *deliberately* infected with a *different* coronavirus squirted into their nose, with immunity monitored for a year. Immunity reached a maximum at 2 weeks. It had lapsed by a year later. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2271881/pdf/epidinfect00023-0213.pdf … .... 25/pic.twitter.com/Cbw70g2vsf
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Amazingly, 9 volunteers returned to lab to be ‘re-challenged’ by having virus squirted into their nose a second time! Although their antibody titers had declined, they still had some immunity, since only 6 of 9 became re-infected and none developed symptoms. So, that’s great! 26/
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Alas, as an aside, the decline in titers also means that developing a vaccine for COVID19 may be very challenging, similar to the reasons we do not yet have a vaccine for the common cold (but that is the topic for another thread). 27/
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Serological tests are important even in acute phase of COVID19 because tests for virus itself could be falsely negative (for many clinical & technical reasons, eg poor technique swabbing throat). Detecting antibodies to the virus offers us another way to spot the little devil 28/
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As the epidemic proceeds, we will want to do serological tests (by drawing blood) on as many people as possible to identify people who have recovered and are highly likely to be immune. This should be a national priority. 29/
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People who are known to be immune based on such serological tests for SARS-CoV-2 are no longer infectious (they basically cannot spread the virus), and they can return to work, school, etc. This is going to be especially valuable for health care workers. 30/
24 antwoorden 528 retweets 2.435 vind-ik-leuksDeze collectie tonen
Hi Prof. Specifically what do you mean by immune and non-infectious? Is it defined by ab titre, RNAemia, days sinceab detected?
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