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Coronavirus: Science Explains Why Recovered Patients Are Not Immune

Evelyn

May. 24, 2020

Signs of at least temporary immunity after COVID-19 infection.  2003 SARS outbreak antibodies also help to block the virus that causes COVID-19.  Preliminary vaccine trial results are out, but there remains a long way to go.
Evidence builds for natural immunity after infection
It is still not clear whether people infected with coronavirus are immune to the virus after they recover. It’s a key scientific question that needs to be addressed, especially as many health policies around the globe have been based on the assumption that populations will develop “herd immunity” over time.
New research from the Korean Centres for Disease Control and Prevention this week suggests that people who are re-infected with coronavirus are not infectious the second time around, and are - at least temporarily - immune.
Researchers tried to isolate infectious coronaviruses from samples taken from 108 people who retested positive after having been discharged from isolation. All of those samples tested negative. When the scientists examined 23 of those patients for antibodies against the coronavirus, almost all had neutralizing antibodies that prevent the virus getting into cells.
The team also tracked down 790 people who had come into contact with 285 people who retested positive. Of those contacts, 27 tested positive for the coronavirus, but none of these new cases appeared to originate from the reinfected patients, suggesting that those patients are likely not contagious.
SARS antibody also blocks new coronavirus
Researchers at the University of Washington in Seattle have found that an antibody from the blood of a SARS-survivor could help fight COVID-19.
Like the current pandemic, the 2003 SARS outbreak was caused by a coronavirus. T he peer-reviewed study indicates that although the two viruses are distinct, the newly identified antibody (which they’ve named S309) can recognise and block both.
Antibodies block the virus by attaching to a ‘spike’ protein on the surface of the virus, preventing it from entering human cells. The researchers’ analysis shows that S309 binds to a different location than other known coronavirus antibodies. By combining S309 with other antibodies the researchers demonstrated that the antibody “cocktails" were more effective in blocking the virus than any of the antibodies alone. The researchers stated this offers some hope that S309 could help curtail the COVID-19 pandemic and also pave the way to better preparedness for future coronavirus outbreaks.
Have you read?     ‘Building back better’ – here’s how we can navigate the risks we face after COVID-19    An expert in infectious animal diseases answers questions on this pandemic – and the next one    5 curve-flattening technologies being developed by young people
First human trial vaccine results
Eight volunteers have produced an antibody response to Moderna’s RNA vaccine as part of a first-stage trial of 45 people run by the National Institutes of Allergy and Infectious Diseases in the United States.
The results offer a glimmer of hope in getting closer to finding a vaccine that will end the COVID-19 pandemic, but experts caution that the results should be "taken with a grain of salt": only eight people produced an antibody response, there is no way of contextualising the findings and no way of telling how durable the response will be.
Time will tell how the vaccine fares, with Moderna intending to start the next stage of human trials involving 600 people shortly, and a much bigger trial involving thousands in July. The Moderna RNA vaccine is just one of 115 vaccine candidates registered with the World Health Organization (WHO) but the first to go to human trials. Stay tuned...

   The theoretical timeline to which scientists are the world are working to produce a COVID-19 vaccine.  Image: Wellcome Trust
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