If, as the WHO suggests, antibodies don’t prevent reinfection of COVID-19, does that mean a vaccine is not possible?
My evaluation of this link as a non-doctor leads me to believe the consensus is “we dunno.”
It’s not a yes or no proposition. The current evidence seems to be that, like for most viruses, antibodies usually prevent reinfection, but also like most viruses, they don’t always. It might reasonably be that 10% of the population, say, could still be vulnerable to reinfection even after developing antibodies. Which would still mean that a vaccine could work for 90% of the population, which would be plenty high enough to beat this thing. Vaccines don’t need to work for everyone.
[Moderating]
Oh, and moving to Quarantine.
I assume the people working on vaccines believe they will be effective based on other work with Covid strains. I think the WHO doesn’t want a bunch of idiots running around infecting people because they had a mild cough and a fever a couple months ago.
Thanks, it sounds like the WHO is just putting some distance between immunity and having a positive result on an antibody test. A reasonable caution.
Note that this is not what the WHO is suggesting. From your link:
WHO is not saying that antibodies prevent reinfection, and they are also not saying antibodies do not prevent reinfection. They are saying that they believe there is no (statistically significant) evidence available upon which to make a judgement.
First let’s clarify what that WHO statement says and does not say. It DOES NOT suggest that “antibodies don’t prevent reinfection of COVID-19.” In fact there is as of this time no credible evidence of significant reinfection risk, with or without antibodies measurable. That is a far thing though from the impression given with a “risk-free certificate.”
It states instead that there is not solid evidence that antibodies make one completely “risk-free” and appropriately caution that such is not known. There may be a risk, maybe is likely some, and if so we don’t yet know what the size of it could be, or how it changes over time. Those with past infection, be they antibody positive or not, should not assume that they have no risk of becoming reinfected perhaps even more so including asymptomatically so. If those who test for antibodies believe they are 100% invulnerable to reinfection, then they might engage in behaviors that put vulnerable others at avoidable risk. If you had a past infection you are a much lower risk person, but there is no reason to believe you are a zero risk person, of getting it and spreading it.
To answer the question of the title though. The easy thing to measure as a proxy for immunity is the level of antibody response, the titers. That’s a measure of “the humoral response” which is produced by B-cells, and those antibody levels are thought to do much of the heavy lifting of protection from infection in most cases. Some people though are immune without titers that such a test would consider positive, because they are still protected by an induced “cellular response”, mediated more through T-cells. That is much harder to measure but often more lasting in terms of protection. It is very difficult to really know how much of the protection from vaccines is due the proxy of its efficacy (the antibody level response), and how much from the cellular response. Here’s one example of how that is established for Hepatitis B, in which “HBsAg-specific memory T cells remained detectable in the circulation for a long time after vaccination, even when serum anti-HBs level had been undetectable.”
So to the question, while it would be very surprising if some very significant degree (not 100%) of protection was not correlated with positive titers, there are indeed immunization induced protections that are separate from having measurable antibody responses.
Thanks, DSeid and Caldazar.
My layperson’s understanding of your responses is that antibodies are an imperfect measure of immunity (and not just for COVID-19) and that vaccine-based immunity is not a binary thing. Feel free to set me straight. I appreciate your responses.
Is there any basis to hope that if future reinfection IS possible or turns out common , say after some amount of months, despite presence of antibodies, that there could be a substantially lower risk of serious infection or death in those cases in general due to some degree of protection already established? It seems all discussion I’ve seen of reinfection doesn’t take this in to consideration, so maybe there’s no basis for that, but if there is, that alone would make a vaccine pretty effective even if it doesn’t prevent infection
Echoing Bootis’s question and adding one of my own, could the multiple mutations that the virus is displaying mean that a Covid vaccine might be similar to a flu shot, needs to be taken every year and the protection is iffy?
leswax, yes. And that the WHO statement is a reminder of the importance of the “we dunno” qualification more than anything else.
Bootis and AK84, for values of “could” and “might”, yes. (Illustrating that “we dunno” importance again!)
In general yes, reinfection after previous infection is usually milder. Easy example from recent influenza history - the favored explanation for why H1N1 relatively spared older adults, killing younger adults more commonly than other influenzas do, is that it was similar to an influenza they had seen way back in their childhoods, and that memory T-cells around still from then provided some partial protection. Younger adults had never seen it before. That said there are always counter example exceptions for those who want to worry! Dengue is an unusual but often mentioned case in which having had a first infection with the “right” amount of very slight immune response, makes a second infection worse. In terms of herd immunity the issue though is less how sick it makes you if reinfected, and more how much less contagious it makes you if reinfected. Also not necessarily or even likely binary.
My understanding is that SARS-CoV-2 mutates at the key target locations less often than influenza does, and the hope is that it means protection will be more long lasting. But yup in the they dunno for sure group. That said another recent influenza history bit to go by - in the years that influenza is “a miss” because the a new mutation came out after the vaccine was out, it is still true (in kids for sure anyway) among those who have been vaccinated compared to those not.
It might be that disease doesn’t confer immunity. It might be that we can make vaccines that aren’t helpful, or are worse than unhelpful. It’s still possible that we may be able to make a vaccine that is helpful, and it may take a while.
For example, antibodies might prevent sickness, but not re-infection. You’ve heard about people with C19 infections but no symptoms? A vaccine might give you that.
In which case a vaccine would be possible, and useful, but wouldn’t be an immunity passport.
Or an inhaled vaccine might localize in the lungs, and prevent lung infection. Which would be useful, and prevent transmission, but might not show up very well on a blood test. In which case again, it might not be any good for an immunity passport.
I’ve got a TB vaccination scar, and a smallpox vaccination scar. Back in the day, before there were antibody tests, those scars and an initialed paper record were the visible indications that I had been vaccinated. Real disease and vaccination and travel documents aren’t all exactly the same thing.
Missed phrase added. Sorry.
Curious about the TB scar. I’m old enough to have received the smallpox vaccine but I never heard of any mass TB vaccination program where I lived. Did your area have such a program, or did you get it because of a local outbreak, or are you in the medical field?
They used to do a four-pronged tine test to see if you had tuberculosis back when I was a kid, but I think they’ve discontinued that since tuberculosis is so uncommon in the US these days (primarily in immigrants). Other countries do immunize against it though if they see more endemic tuberculosis. But even there, it’s just an injection into your deltoid like a flu shot or tetanus shot or whatever. No scar.
I remember (and got) the tine test as well, I just don’t remember it leaving any permanent mark.
Some countries and professions vaccinate against TB.
The mantoux test only leaves a large scar if you get a massive reaction, as you might (???) if you have active TB. I have a small scar, barely visible, only because I know where to look, and because I had a small reaction because of my previous TB vaccination.
I got the TB vaccination in Australia, and in Australia the TB vaccination commonly caused a large scar. I think that perhaps the vaccine was different in Australia than it was in the USA, but I don’t know: perhaps the method of delivery was different.
Routine TB vaccination stopped many years ago in Australia. Australia does not have endemic TB. Did the USA ever have routine TB vaccination? The USA still has endemic TB, but it’s restricted to poor people and prisoners,
This site Recognizing Old Vaccine Scars - VAXOPEDIA has a good photo comparing the scar from the BCG (TB vaccine) and the scar from the smallpox vaccine. Apparently the smallpox one is depressed and has some star like arms radiating off, and the BCG one tends to raised. Learn something new every day!
There is speculation that having had the BCG may provide some COVID-19 protection. Not in a specific vaccine way but still.
There is also some thought that the oral polio vaccine (OPV) may provide protection against SARS-CoV-2 for a limited period of time (a few months at best) by activating the innate immune system based upon little known research in Soviet Russia by Dr. Konstantin Chumakov.
It is too early to know whether this will be efficacious in providing protection but it is something worth doing controlled studies upon at-risk populations (using the bivalent PV-1/PV-3 oral vaccine). This vaccine is extremely safe and because it was used in the now-suspended poliovirus global eradication campaign, there should be plenty of doses available for use.
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