As a second coronavirus wave is already hitting, and the number of infections keeps on growing everywhere around the globe, searches are still going on about this vibrus that keeps on shaking up our societies. And among the most striking studies, those about Covid-19 immunity as well as its length. According to recent studies, one being American, the other Canadian, immunity usually lasts three months.
But a new and British study released this Tuesday October 27, 2020 by the Imperial College London and Ipsos Mori has outdone the previous ones explaining this immunity to the novel coronavirus reduces rather quickly, especially in asymptomatic people. Immunity could then only last a few months.
How did they made it to such a conclusion? Both institutions have studied over 365,000 participants randomly selected across England. They had to test themselves at home to check if these people had antibodies against coronavirus . "Over this period, the proportion of people who tested positive for COVID-19 antibodies declined by 26.5%", the study says in a press release shared by the AFP, moving from 6% to 4.4% of the group tested.
The study also proved that "people who did not show symptoms of COVId-19 are likely to lose detectable anitbodies sooner that those who did show symptoms". All in all, in people who developed symptoms, the amount of antibodies reduced by 22.3% in the three months of the study. It rises to 64% in people who did not show symptoms. A study that also shows that elderly people are the most impacted, with a number of people ageg 75+ who developed antibodies dropping by 39%. "This study is a critical piece of research, helping us to understand the nature of Covid-19 antibodies over time" junior health minister James Bethell said.
On June 18, several Asian searchers disclosed the background of a new study released in Nature Medicine. According to it, cases infected by Covid-19 that are asymptomatic may show a lower antibody rate than people who developed symptoms. To confirm these hypotheses, searchers work on 37 asymptomatic cases which infection has been confirmed by a virologic test before April 10, 2020 in the Wanzhou district. Among these 37 asymptomatic cases, the study included 22 females and 15 males with ages ranking from 8 to 75 years.
When being isolated at the hospital, searchers noticed that patients had a median 19-day virus shedding, against 14 days in the 37 patients showing symptoms (fever, cough, shortness of breath…). Then, eight weeks after being discharged from the hospital, neutralizing antibody levels – said to enable immunity against the virus – dropped down by 81.1% in asymptomatic cases, against 62.2% in symptomatic cases. “In this study, we observed that IgG levels and neutralizing antibodies in a high proportion of individuals who recovered from SARS-CoV-2 infection start to decrease within 2–3 months after infection.” they write.