I feel funny asking this question, in light of current events. But my question is purely in fictional context. I'm just trying to make sure it aligns with reality.

I have a character who was successfully treated for deadly virus. I'll call her "Jane." Now, her body has created antibodies for the virus. Jane is donating her blood to help someone else who was infected, as the antibodies in her blood can help this person's body fight the sickness.

Here's the catch. Jane is pregnant. The person being treated is in quarantine, but would it be safe for Jane to be around the person without being suited up? It think the way antibody immunity works, is that if you have sufficient antibodies, they fight off the disease before you can be infected. But if you're carrying an unborn child, would it be risky for the pregnancy?

I know all antibodies aren't created alike -- such as Hep C antibodies, which don't protect against re-infection. But if Jane has effective antibodies, would this make her and her child both safe?

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    $\begingroup$ One for medicalsciences.stackexchange.com ? $\endgroup$ – BIOStheZerg Aug 12 '20 at 13:45
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    $\begingroup$ Like you said, not all antibodies are created equal. There are cases of reinfection even for COVID, just after a couple months of a person being cured. $\endgroup$ – The Square-Cube Law Aug 12 '20 at 13:56
  • $\begingroup$ @BIOStheZerg, that's a fair suggestion. But I posted in Worldbuilding because utilmateiy, this circumstance takes place in a fictional setting, where drama and plot need to be considered as much as fact. That's just my take :-) $\endgroup$ – cal Aug 12 '20 at 15:15
  • $\begingroup$ Then it's your decision as a writer. In the real world antibodies go down with time. $\endgroup$ – NomadMaker Aug 12 '20 at 21:55
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    $\begingroup$ Antibody reactions are extremely complex, and can't even guarantee that Jane won't get reinfected, even if she has antibodies. Jane doesn't need to be in infective contact to give a plasma transfusion, in fact it would be very difficult to make a direct transfusion of whole blood like that. They collect convalescent plasma in a donation center, and give it as a directed donation to someone with a compatible blood type. Donation rules for plasma are inverse for packed cells - AB plasma is universal donor, although reactions with A plasma are quite low and it is frequently used instead. $\endgroup$ – DWKraus Aug 12 '20 at 23:44


So, all infections and therefore all antibodies are not equal. There are a few talking points to discuss about this question.

Saying that you "have antibodies" is an incomplete statement. If your body is able to learn how to create antibodies for an infection, many people then say that you "have antibodies" and should never be reinfected, but:

  1. Your body does not perpetually "have antibodies" after an infection.
    After your body is done with an infection, the antibodies that were produced begin to go away. The longer it has been since the infection, the less of those antibodies are in your system at a given time. Some antibodies will stay around forever in small quantities, others might go away entirely until reinfection.

  2. Prevention of reinfection after losing antibodies is dependent on: 1, storing the information on how to make more antibodies...
    When your body made the antibodies for the infection, it was able to do so because it "had instructions" on how. Sometimes your body can/does store the information on how to make these antibodies again in case of reinfection, other times it does/can not.

  3. ... and 2, the infection-causing microbe (virus, bacteria, fungus) having not mutated since last infection.
    Even if your body is able to recreate the antibodies, it will do no good if the strain that caused the infection has mutated in such a way that the same antibodies no longer work against it.

To answer your specific question about Jane:

If it has only been a short while since Jane's infection, two things could be assumed: the new patient's strain would not be a mutated variety, and Jane still has a sufficient amount of antibodies in her system as well as the instructions to make more. As long as those conditions are met, then her and her baby are protected by the antibodies in her system, but ultimately should avoid as much contact as possible to err on the safe side. Otherwise, if it has been a long enough amount of time that amount of antibodies has decreased and the virus may have mutated, then it's an inherent risk that Jane might get reinfected.

Also, as others have discussed, once the baby is born, it is possible, but not guaranteed that this specific antibody could be passed to the baby through breastfeeding.

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    $\begingroup$ Great answer! It should be noted that mutation speed varies widely; the flu family is notorious for it, whereas others don’t and are thus may only need one vaccination (or past infection) to protect for life. $\endgroup$ – StephenS Aug 12 '20 at 18:33

Yes, the fetus would be protected by maternal antibodies.

https://en.wikipedia.org/wiki/Passive_immunity is immunity of a fetus or newborn by virtue of maternal antibodies. These antibodies cross the placenta. They persist in the newborn for a time after birth.

Passive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin (obtained from humans, horses, or other animals) are transferred to non-immune persons through blood products that contain antibodies, such as in immunoglobulin therapy or antiserum therapy.[1]

The same passive immunity Jane is going to use to help the sick person also protects her baby.

It would be pretty sweet if the T cells responsible for those antibodies could also go thru the placenta and take up residence in the baby. Then we would have ancestral immunity. It would be even sweeter if this were happening now and could be demonstrated - circulating immune cells of maternal origin.

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    $\begingroup$ And maternal antibodies are also expressed in breast milk; that's why the WHO strongly recommends breastfeeding instead of relying on powdered milk. $\endgroup$ – AlexP Aug 12 '20 at 14:31

It would make them both safer

Generally speaking (that's important!), antibodies do not grant immunity. They grant resistance. If enough people enjoy that resistance then society becomes immune ("herd immunity"). Diseases like polio, scarlet fever, and measles were declared overcome due to so many having the antibodies and didn't start to rear their ugly heads again until the blankety-blank anti-vaxers started claiming they had the right to threaten the herd.1

What has happened is important to understand. Because antibodies provide only resistance, not immunity, anybody can get sick when a chink in the herd-immunity armor is created. It would be convenient if all the anti-vaxer's children were the people getting sick, but just as COVID-19 has underscored the complications of asymptomatic carriers, the reality is that the anti-vaxer children become the foothold, but not necessarily the place where the battle is fought.

But even if we ignore the anti-vaxers, it's always possible for an individual to become ill from a disease for which they have antibodies. All those diseases I mentioned (and a great many more) were statistically wiped out, but not completely. Occasionally someone would contract polio, scarlet fever, or measles.

This is why Jane and her baby would be safer, but not necessarily immune.

Frankly, put a person teeming with antibodies in a room full of sick people related to those antibodies and the odds are quite good that person will get sick — but the antibodies do make it quite a bit harder. Concentration of exposure, length of exposure, general strength/health of the body, age of the body, etc, all have an impact, too.

However, if what you're looking for is a rationale to keep Jane and her baby safe from a disease in your story — antibodies are a perfectly good suspension-of-disbelief solution to the problem.

1I need to be fair. What they're claiming is parental rights to determine the medical assistance and/or interference government can impose on their children. In almost any other context, that would be an important and valuable demand. Unfortunately, this is perhaps the one and only context where it's such a bad idea that We, The People might need to impose societal authority.

  • $\begingroup$ I understand what you're saying. I also agree that terrible diseases such as polio have vaccines to thank for their near eradication. But it's also imperative that we are educated on when it's completely necessary to get a vaccine and when the side-effects don't make a certain shot worth it. Imposed vaccinations can be the edge of a very slippery slope. This is a complicated topic, though, which can't be covered in a short discussion. Thanks for you input. $\endgroup$ – cal Aug 12 '20 at 15:22
  • $\begingroup$ @cal Only poorly educated people think the issue is complex. Every study that's ever been performed has proven beyond every reasonable doubt that the benefits of mandated vaccinations so vastly outstrip the rare side effects of individual vaccination that only the politically-driven would believe there's a sensible, personal choice. There are always individual sacrifices to be made to enjoy the benefits of society - and a never-ending stream of people who believe they should have the right to strip the cream off the top without having to be responsible for that sacrifice. I've said my piece. $\endgroup$ – JBH Aug 13 '20 at 4:53
  • $\begingroup$ I understand you, but I'm not convinced. But if it's the poorly educated who think the issue is complex, then why would mandated vaccinations be so important? Wouldn't a fair stance be to simply educate those who have doubts about vaccinations? And if, after such an offer of education, they still turn down something that is claimed to be life-saving, then their group would just have to face the natural consequences of their decision. Meanwhile, those in favor of vaccinations would get vaccinated. This is merely covering the area regarding our rights...which is no small area to consider. $\endgroup$ – cal Aug 13 '20 at 18:39
  • $\begingroup$ I'll also add (I ran out of room!) that when it comes to the good of mankind, it's arguable that just as many have died under oppression as they have from disease. Our human rights are as fragile and valuable as our health. Maybe even more so. $\endgroup$ – cal Aug 13 '20 at 18:46
  • $\begingroup$ @cal No individual has the right to put another at risk. That's why it's illegal to yell "fire!" in a crowded theater or drive on the wrong side of the road. The governed give that authority to the government (whose only method of solving problems is through threat of violence, great and small). There is well-documented proof that vaccination works (the lack of polio...) and most complaints of individual vaccination risk are dubious (like Autism, which has been proven completely false). Educating the ignorant only works when the ignorant want to be educated. (*continued*) $\endgroup$ – JBH Aug 14 '20 at 12:27

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