Post by mhbruin on Jun 24, 2020 13:29:10 GMT -8
The paper in question comes from a group of Chinese researchers at Chongqing Medical University. They looked at a group of patients who tested positive for the SARS-CoV-2 virus, but never displayed any symptoms of COVID-19. These weren’t just patients who were pre-symptomatic—that is, in the early days of their infection with symptoms still to come—but asymptomatic over the course of their infection.
The biggest thing that turned up in the paper, and the part that has gathered both press and concern, is a statement that 40% of asymptomatic individuals, and 13% of those with symptoms, became negative for a particular COVID-19 antibody “in the early convalescent phase,” that is, just two or three months after their infection.
But there are several caveats here. In fact, it’s caveats all the way down.
First of all, the size of this study was extremely small. There were just 37 asymptomatic individuals, and 37 symptomatic individuals included in the study. It’s large enough to raise questions that can be addressed by additional studies, but far too small to be cited as an indication of general results.
Secondly, “symptomatic” in this case means “mildly symptomatic.” These aren’t patients who did a lap through the ICU, or even those who suffered from severe flu-like symptoms. The symptomatic group in this study was just one notch removed from the asymptomatic group in terms of the disease they experienced. All of the participants in this study had very mild cases of COVID-19 as far as symptoms.
Third, age could well have been a factor in these results. Previous studies have already demonstrated that those patients with very mild cases of COVID-19 are likely to have low levels of antibodies. An April study, also from China, indicated that a large percentage of patients with milder symptomatic responses also had much lower levels of antibodies. That study also showed that lower levels of antibody development appeared to occur in younger patients, with patients over 60 having three times the amount of antibodies as those under 40, even when both groups had mild cases of COVID-19. The median age of individuals in the new paper was 41—meaning that fully half of all the patients were already in the group that earlier studies indicated as generating a smaller immune response.
Finally, all of the patients in this group had tested positive at some point using an RT–PCR test, but the accuracy of either that test, or the antibody tests used in the results, cannot be confirmed. Suffice to say that the antibody tests in particular have not been subject to large-scale open review.
The biggest thing that turned up in the paper, and the part that has gathered both press and concern, is a statement that 40% of asymptomatic individuals, and 13% of those with symptoms, became negative for a particular COVID-19 antibody “in the early convalescent phase,” that is, just two or three months after their infection.
But there are several caveats here. In fact, it’s caveats all the way down.
First of all, the size of this study was extremely small. There were just 37 asymptomatic individuals, and 37 symptomatic individuals included in the study. It’s large enough to raise questions that can be addressed by additional studies, but far too small to be cited as an indication of general results.
Secondly, “symptomatic” in this case means “mildly symptomatic.” These aren’t patients who did a lap through the ICU, or even those who suffered from severe flu-like symptoms. The symptomatic group in this study was just one notch removed from the asymptomatic group in terms of the disease they experienced. All of the participants in this study had very mild cases of COVID-19 as far as symptoms.
Third, age could well have been a factor in these results. Previous studies have already demonstrated that those patients with very mild cases of COVID-19 are likely to have low levels of antibodies. An April study, also from China, indicated that a large percentage of patients with milder symptomatic responses also had much lower levels of antibodies. That study also showed that lower levels of antibody development appeared to occur in younger patients, with patients over 60 having three times the amount of antibodies as those under 40, even when both groups had mild cases of COVID-19. The median age of individuals in the new paper was 41—meaning that fully half of all the patients were already in the group that earlier studies indicated as generating a smaller immune response.
Finally, all of the patients in this group had tested positive at some point using an RT–PCR test, but the accuracy of either that test, or the antibody tests used in the results, cannot be confirmed. Suffice to say that the antibody tests in particular have not been subject to large-scale open review.
