In the Tuesday House hearing on the status of the COVID-19 crisis there were a few notes of “cautious optimism” sounded by Dr. Anthony Fauci around the possibility of a vaccine becoming available at the end of the year. But, when contrasted against the rising tide of cases across the South, that optimistic note seems a bit plaintive. Fauci was clear that, even as we talk about a vaccine, we still don’t understand how exactly how much those who have already had COVID-19 are protected against a reinfection of the disease. We don’t know which kind of antibodies provide protection. We don’t know what level of antibodies are effective. We don’t know how long this protection lasts.
It doesn’t seem surprising that, at the same hearing, a question came up based on a paper published a week ago in the science journal Nature. This paper, which contains evidence that antibodies to COVID-19 can fade over a short period of time, has raised fresh concerns over whether people can catch the disease repeatedly, and whether a vaccine is even possible. But a closer look shows that, while the paper does contain some bad news, it really has little to say about vaccines.
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.
These asymptomatic patients have been an interesting, and disturbing, part of the pandemic from its beginning. On the one hand, that 20-40% people appeared to be getting the disease, without really getting sick, appeared to be a good thing. On the other hand, the ability of these patients to transmit COVID-19 has been a key factor in its spread around the world. Four months into the epidemic within the United States, the number of asymptomatic carriers of the disease may be higher than ever, as confirmed cases have skewed ever younger over time.
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.
That’s the kind of statement that should come with Jaws theme music, or at the very least, a sad trombone, because it suggests that immunity to COVID-19 is extremely short-lived. 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.
Taking all that into account, this was a small group of relatively young patients who had very mild cases of COVID-19. Their antibody responses were low to begin with, and within 2-3 months the response of some had dropped below the line of detectability for SARS-CoV-2 specific antibodies. The median decline in antibodies was 8.3% in the asymptomatic group and 11.7% in the symptomatic group. What does this tell us?
Well—assuming that the results can be projected to a larger population—it doesn’t indicate that a vaccine is unlikely, or that people will need booster shots every two months. It may mean that a higher initial immune response may be required to provide immunity over the desired period of at least a year, if not longer. Fortunately, that’s exactly what’s been seen in early results from vaccine tests. (One caveat to that caveat: The Oxford vaccine has produced low levels of response in some patients, equivalent to a very mild or asymptomatic case). These results also don’t tell us whether those with a high level of response maintain it over a longer period of time or … honestly, there are a lot of things we don’t know here.
This study may provide a partial answer to one of the questions that Fauci mentioned in Tuesday’s hearing: What level of antibiotics are effective? Assuming these results hold up, they may say that low levels of antibodies lose their effectiveness too quickly, and that a higher level of response—the kind of response that patients displaying stronger symptoms generate—may be required if a vaccine is going to “stick.”
However, there is nothing here to say that either a vaccine isn’t going to work, or that we should all look forward to a life of being regular pincushions.
Still … there is some bad news in this study. Those falling rates of antibodies may mean that asymptomatic patients really can become infected, and become carriers, again. These patients could be regular COVID-Mary and COVID-Marvins if they’re repeatedly asymptomatic carriers of the disease. The study also showed that these asymptomatic individuals seemed to be contagious longer than patients who displayed symptoms.
The last bit of bad news in the study has nothing to do with antibodies and everything to do with just what a rat bastard of a disease this really is. Even among the asymptomatic group, two-thirds of patients had signs of damage in one lung, one-third had signs of damage in both lungs. That’s everyone. Everyone who had COVID-19 in this study, even the ones who had no symptoms, displayed signs of damage in CT scans. There may be asymptomatic cases of COVID-19, but there don’t seem to be any really “mild” cases.
Wednesday, Jun 24, 2020 · 5:36:48 PM +00:00 · Mark Sumner
Sorry, I misread a portion of the study. It was not 100% of the patients who had visible occlusions in the lungs. It was 100% of a subset, or 58% of the total of asymptomatic patients. Leaving the error in place for those who have already caught this. Thanks.
