Researchers have found that newborns born to COVID-19 positive mothers were born with antibodies—and this could be huge.

A study published in JAMA pediatrics analyzed blood samples in 1471 mother-baby pairs. COVID-19 antibodies were found in the blood of 83 of the mothers (representing both symptomatic and asymptomatic cases of COVID)—and of these 83 women's babies, 72 had antibodies present in their blood. This means that these newborns may have been born with some immunity to the virus. It is possible that these antibodies were passed through the placenta, which presents very interesting data in the fight against COVID-19.

Previously a smaller systematic review looked at the results of 33 studies; they found that 10 of 11 babies born to mothers with COVID-19 had COVID-19 antibodies present at birth while testing negative for the virus.

Before we explore what this might mean, let's take a quick look at the science behind it. It's the same science that is involved with vaccines, and the science that is going to get us past this pandemic—so it's going to be at the forefront of our attention for a while.

What are antigens and antibodies?

Viruses, like COVID-19, contain antigens, molecules made of protein, peptides or polysaccharides, that trigger immune responses in the body. Think of antigens as warning flags; they enter your body, your body detects them and says, "Wait a second, you don't belong here," and then mounts an immune response (in the form of antibodies) to get rid of the culprit that brought them in (i.e. the virus). (Many biological properties contain antigens: bacteria, allergens and more).

How does an immune response happen?

When antigens enter your body, they attach to white blood cells called B lymphocytes (or B cells). This causes the B cells to start dividing into a type of cell called a plasma cell. Plasma cells then start to produce antibodies, whose job it is to track down antigens; when they find one they grab onto it, which alerts the rest of the immune system that an invader has been located. A battle ensues, and hopefully, your body is able to destroy the virus and get you back to being healthy. (Of note, there are times when this immunologic response actually harms us, like in the case of autoimmune diseases. But for our purposes here, we're going to focus on bad stuff like viruses.)

There are several types of antibodies, but the two we hear most about, especially right now, are IgM and IgG.

IgM antibodies are fast and fairly immediate. They are the first antibodies to the scene. They help with the initial fighting of the virus, and they make the body produce IgG antibodies.

IgG antibodies are longer-term helpers. Their levels spike during an infection, but then they hang around in the body, waiting; the next time your body detects an antigen it's seen before, the IgG antibodies say, "Oh, we know you!" and your body's response is much faster. I love the way the Merke manual describes this: "The body retains a catalog of IgG antibodies that can be rapidly reproduced whenever exposed to the same antigen." The hope is that this second exposure will cause a far less severe (or even non-existent) illness for your body because your immune system already knows how to fight it and can respond a lot faster.

This is how vaccines work.

One very important (and wildly cool) factor to know about IgG antibodies is that they are the only antibodies that can pass through the placenta. They do this so that the fetus can start to gain antibodies their pregnant parent has already acquired. (Come on, how cool is the human body?!)

And this brings us back to the recent findings of babies having COVID-19 IgG antibodies at birth.

How does this finding impact COVID-19?

The findings of this research indicate that pregnant people with COVID-19 may pass IgG antibodies to their fetus via the placenta: This means that these newborns may be born with the ability to fight the COVID-19 virus.

This is super exciting, but with some caveats. First, the sample sizes of these two studies were small—83 and 11. This makes it harder to know if the findings can be generalized (in other words, it could just be a coincidence and we can't imply that these finds apply to the population at large… yet). We don't know for certain that the antibodies were passed through the placenta. Also, these findings are very new: The studies were published in January of 2021 and October of 2020. This means that we don't yet have long-term information about outcomes for these babies.

We also don't know what the implication is for these findings: Is it just interesting, or is there a major protective factor at play that will have a dramatic impact on the fight against COVID-19? It's unclear right now.

But in a new pandemic (yes, it feels like ages, but really COVID-19 is still very new to us) with grave consequences, new findings like these are exciting. They add to the current data we have and might help scientists and health care providers in their quest to support pregnant people and infants during the pandemic.

This story was originally published on November 30, 2020 and has been updated.