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Munich (dpa) - According to a large-scale antibody study, just under 3.3 percent of Munich's residents were infected with the corona virus by November.
This means that the number of those who have developed antibodies against the Sars-CoV-2 virus has almost doubled since the first wave, said the researchers from Infectious and Tropical Medicine at the Munich University Hospital.
It is the first large study nationwide that provides results on the number of infections in the second wave.
At the beginning of the new test round, around 1.5 percent of Munich residents were registered as Corona-positive with the health authorities.
That made the actual number about twice as high.
In the first round, the proportion of infections detected in the study was four times higher than known.
"If you only compare the increase in infections since the beginning of June, the rate of undetected infections has fallen even more significantly," said the researchers.
The fact that the number of unreported cases is now lower also shows that the test strategy in Bavaria is proving its worth, said study leader Michael Hoelscher.
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In a first round of the study from April 5 to June 10, the scientists working with Hoelscher examined around 5300 people from representatively selected households.
By this time, a good 1.7 percent of people had developed antibodies.
According to a new calculation, the mortality of infected people in the first round was 0.47 percent - and thus many times higher than that of seasonal flu infections.
In the spring, the researchers had personally appeared in teams in households to draw blood from people, but at the beginning of November they sent the test participants a kit for drawing their own blood by finger pricking with the request to dab a few drops of blood on a filter paper and send it back by post .
By December 9th, a good 4,250 blood samples had been received.
According to Hoelscher, the study also showed that the amount of antibodies in the blood does not drop sharply after a few months, as previously assumed.
Anyone who tested positive for antibodies in the first round usually also did so in the second phase.
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It practically never happened that about six months after the first test in patients no more antibodies were detectable, said Hoelscher.
It remains to be seen whether the detectability of antibodies also means that those affected are immune.
Further and more complex tests would be necessary to determine immunity.
The study, in which Helmholtz Zentrum München is also involved, will be continued.
Tropical Institute at the LMU Munich Clinic
Study at the Tropical Institute