What is the scientific community’s understanding of COVID-19 antibodies? My layman’s understanding of virus antibodies, in general, is that the presence of antibodies indicates the body has encountered a virus, mounted an immune response, and is then prepared to fight the same bug again. Antibodies fade over time, but the immune system “remembers” how to produce the cells needed to fight the same infection. Thus, the presence of antibodies implies immunity going forward.
Is this the correct way to think about antibody testing for COVID-19? Is there any reason to believe this virus is different from the hundreds of other viruses in the world in this regard? I’m aware of a report of someone in Asia (?) being infected with COVID-19 twice, but I haven’t come across definitive reports of it happening on anything close to a large scale.
If antibodies don’t imply immunity, what are the implications for vaccination? My understanding is that the purpose of a vaccine is to introduce a benign version of a virus to the immune system but cause the same immune response, thus conferring immunity. If the presence of antibodies doesn’t mean someone is immune, what’s the point of a vaccine?
I’ll let the real medical experts chime in on the other points but this point isn’t true. Immunity can fade over time which is why some vaccines require booster shots. Also, a quickly mutating virus may require new vaccines as the old antibodies no longer offer protection.
The part you may be missing is that antibodies are just one part of immune response. The white blood cell response is separate from but also very important.
As it applies specifically to COVID
It’s easy to measure the volume of antibodies in your blood right now. It’s very hard to measure how well your immune memory system remembers what to do next time. IOW, how well it will notice and react if you are infected later. Bottom line: current antibody levels are (mostly) NOT predictive of longer term antibody response.
Antibody levels say exactly zero about the other WBC-mediated immune response system. And it’s currently very hard to test how this system, while resting, would respond to a later infection.
Recent research has shown that for COVID specifically, the WBC repsonse (my #2) is probably more important, maybe much more important, than the antibody response system (my #1)
Disease severity is poorly correlated with any of the above. Some people with objectively weak immune systems have few or no symptoms, other people with objectively strong immune systems get hammered, often to death. IOW, there’s more going on to COVID disease severity than can be predicted by 1, 2, or 3.
In short, focusing on easy-to-measure antibody levels as a metric of an individual’s COVID safety is like the drunk looking for his car keys under the streetlight rather than in the dark parking lot where he knows he dropped them. The light’s better there, but that doesn’t answer the real question.
On a related note, there is little doubt that it’s possible to get covid twice. I personally have a good friend who just tested positive after having been positive in March/April, and I know of numerous other people second-hand (e.g. my wife’s friend’s SIL, and similar such).
That said, there is also little doubt that having been infected once makes you less susceptible to reinfection. I know hundreds of people who have been infected, both in the first wave in March/April and the second wave (where I am) now, and there is very clearly a negative correlation between having been infected once and getting infected again.
This has been a matter for discussion here in NZ in recent days. There is a theory that some (not all) of the positives that occur well after after an initial positive test and symptomatic infection are due to high PCR cycle values (over 35 cycles of PCR replication is a so-called weak positive) in combination with a new (non-corona) viral infection of the nasal cavities/upper respiratory tract triggering the release of viral remnants of the original coronavirus.
This is not to dispute that some people get re-infected with corona-virus. But at least here in New Zealand, the small number of cases of a second positive test have not led to something that could be identified as a second infection of coronavirus, and certainly not an infectious situation.
Although that is a good starting point, they are by no means the same thing, even for antibody mediated immunity. Just as it is possible to create a vaccine that does not give good immunity, it is possible for the body to produce antibodies that do not give good immunity.
The implications for vaccination is that vaccines have to be tested in large trials.
This is actually amazing to me. A coworker’s mother tested positive, and a friend’s son had symptoms, but was never tested. That’s ALL I know about in my circle.
It’s incredible to me that experiences can be so different. On the other hand, I haven’t been on Facebook since sometime in March, so maybe I wouldn’t even know if people were dropping like flies all around me. There’s lot’s of people I don’t keep in regular contact with.
None of these people are people I know through Facebook or any other form of social media. They are all friends, relatives, friends of relatives, relatives of friends, me etc. etc.
Just the people I know who died from it include the stepfather of one BIL and the FIL of another, a clergyman from the neighborhood where I grew up, a couple of guys I knew in school, a guy I knew socially (& FIL of a kid who grew up in the neighborhood), a guy down the block (just last week).
It depends on where you - and your social circle - live.
As I see it there are three problems with checking for antibodies.
First, there is the issue of the quality of the test itself. There are different types of antibodies as well as different types of immune responses as noted above. When we talk about protective antibodies we usually talk about IgG antibodies which circulate in the blood and often show up about 4-6 weeks after an infection. We don’t know how accurate the tests for SARS-COV 2 IgG are but we do know that there are both false positives and false negatives. There may also be some cross reactivity with other coronaviruses. So you don’t know if a positive test is truly positive or a negative test is truly negative.
Second, as mentioned above, we don’t know if the presence of antibodies correlates with immunity. For some viruses, such as hepatitis B or C, we know of specific antibodies that at a certain cut off level indicate that the body has fought off the infection and you can be considered cured and to have protection against the virus. However, with this virus, we don’t know the cut-off level or the timeline which means it is theoretically possible to have IgG antibodies and still shed virus. In addition, we don’t know how long these antibodies last. There are many cases of people testing positive after recovering who may be shedding viral particles and not be infectious. However, there are well documented cases of people testing positive, then having several negative tests then not only testing positive again but also having symptoms. In some people, the virus can actually be worse the second time.
Finally, there are viruses where you form an immune response but the virus remains latent in the body. The herpes viruses, including chicken pox (varicella-zoster) are examples of this. You get a primary infection, develop IgG antibodies, but the disease can reactivate frequently. It is possible that this virus acts in the same way where it is suppressed by antibodies but is still latent in the body and can reactivate in times of stress or in the future,
Therefore, when we talk about antibody tests we really don’t know if the tests are accurate, if a positive test means that you are protected from a recurrence and if a positive test means you will not then give it to anyone else. In other words, continue to social distance and wear your mask.
etc. etc.