Your Vaccinated Immune System Is Ready for Breakthroughs
Getting COVID-19 when youâre vaccinated isnât the same as getting COVID-19 when youâre unvaccinated.
A new dichotomy has begun dogging the pandemic discourse. With the rise of the Ăźber-transmissible Delta variant, experts are saying youâre either going to get vaccinated, or going to get the coronavirus.
For some peopleâa decent number of us, actuallyâitâs going to be both.
Coronavirus infections are happening among vaccinated people. Theyâre going to keep happening as long as the virus is with us, and weâre nowhere close to beating it. When a virus has so thoroughly infiltrated the human population, post-vaccination infections become an arithmetic inevitability. As much as weâd like to think otherwise, being vaccinated does not mean being done with SARS-CoV-2.
Post-vaccination infections, or breakthroughs, might occasionally turn symptomatic, but they arenât shameful or aberrant. They also arenât proof that the shots are failing. These cases are, on average, gentler and less symptomatic; faster-resolving, with less virus lingeringâand, it appears, less likely to pass the pathogen on. The immunity offered by vaccines works in iterations and gradations, not absolutes. It does not make a person completely impervious to infection. It also does not evaporate when a few microbes breach a bodyâs barriers. A breakthrough, despite what it might seem, does not cause our defenses to crumble or even break; it does not erase the protection thatâs already been built. Rather than setting up fragile and penetrable shields, vaccines reinforce the defenses we already have, so that we can encounter the virus safely and potentially build further upon that protection.
To understand the anatomy of a breakthrough case, itâs helpful to think of the human body as a castle. Deepta Bhattacharya, an immunologist at the University of Arizona, compares immunization to reinforcing such a stronghold against assault.
Without vaccination, the castleâs defenders have no idea an attack is coming. They might have stationed a few aggressive guard dogs outside, but these mutts arenât terribly discerning: Theyâre the systemâs innate defenders, fast-acting and brutal, but short-lived and woefully imprecise. Theyâll sink their teeth into anything they donât recognize, and are easily duped by stealthier invaders. If only quarrelsome canines stand between the virus and the castleâs treasures, thatâs a pretty flimsy first line of defense. But itâs essentially the situation that many uninoculated people are in. Other fighters, who operate with more precision and punchâthe bodyâs adaptive cellsâwill eventually be roused. Without prior warning, though, theyâll come out in full force only after a weeks-long delay, by which time the virus may have run roughshod over everything it can. At that point, the fight may, quite literally, be at a fever pitch, fueling worsening symptoms.
Vaccination completely rewrites the beginning, middle, and end of this story. COVID-19 shots act as confidential informants, who pass around intel on the pathogen within the castle walls. With that info, defensive cells can patrol the buildingâs borders, keeping an eye out for a now-familiar foe. When the virus attempts to force its way in, it will hit âbackup layer after backup layerâ of defense, Bhattacharya said.
Prepped by a vaccine, immune reinforcements will be marshaled to the fore much fasterâwithin days of an invasion, sometimes much less. Adaptive cells called B cells, which produce antibodies, and T cells, which kill virus-infected cells, will have had time to study the pathogenâs features, and sharpen their weapons against it. While the guard dogs are pouncing, archers trained to recognize the virus will be shooting it down; the few microbes that make their way deeper inside will be gutted by sword-wielding assassins lurking in the shadows. âEach stage it has to get past takes a bigger chunk outâ of the virus, Bhattacharya said. Even if a couple particles eke past every hurdle, their ranks are fewer, weaker, and less damaging.
In the best-case scenario, the virus might even be instantly sniped at by immune cells and antibodies, still amped up from the vaccineâs recent visit, preventing any infection from being established at all. But expecting this of our shots every time isnât reasonable (and, in fact, wasnât the goal set for any COVID-19 vaccine). Some peopleâs immune cells might have slow reflexes and keep their weapons holstered for too long; that will be especially true among the elderly and immunocompromisedâtheir fighters will still rally, just to a lesser extent.
Changes on the virus side could tip the scales as well. Like invaders in disguise, wily variants might evade detection by certain antibodies. Even readily recognizable versions of the coronavirus can overwhelm the immune systemâs early cavalcade if they raid the premises in high-enough numbersâvia, for instance, an intense and prolonged exposure event.
With so many factors at play, itâs not hard to see how a few viral particles might still hit their mark. But a body under siege isnât going to throw its hands up in defeat. âPeople tend to think of this as yes or noâif I got vaccinated, I should not get any symptoms; I should be completely protected,â Laura Su, an immunologist at the University of Pennsylvania, said. âBut thereâs way more nuance than that.â Even as the virus is raising a ruckus, immune cells and molecules will be attempting to hold their ground, regain their edge, and knock the pathogen back down. Those late-arriving efforts might not halt an infection entirely, but they will still curb the pathogenâs opportunities to move throughout the body, cause symptoms, and spread to someone else. The inhospitality of the vaccinated body to SARS-CoV-2 is whatâs given many researchers hope that long COVID, too, will be rarer among the immunized, though that connection is still being explored.
Breakthroughs, especially symptomatic ones, are still uncommon, as a proportion of immunized people. But by sheer number, âthe more people get vaccinated, the more you will see these breakthrough infections,â Juliet Morrison, a virologist at UC Riverside, said. (Donât forget that a small fraction of millions of people is still a lot of peopleâand in communities where a majority of people are vaccinated, most of the positive tests could be for shot recipients.) Reports of these cases shouldnât be alarming, especially when we drill down on whatâs happening qualitatively. A castle raid is worse if its inhabitants are slaughtered and all its jewels stolen; with vaccines in place, those cases are rareâmany of them are getting replaced with lighter thefts, wherein the virus has time only to land a couple of punches before itâs booted out the door. Sure, vaccines would be âbetterâ if they erected impenetrable force fields around every fortress. They donât, though. Nothing does. And our shots shouldnât be faulted for failing to live up to an impossible standardâone that obscures what they are able to accomplish. A breached stronghold is not necessarily a defeated stronghold; any castle that arms itself in advance will be in a better position than it was before.
Thereâs a potential silver lining to breakthroughs as well. By definition, these infections occur in immune systems that already recognize the virus and can learn from it again. Each subsequent encounter with SARS-CoV-2 might effectively remind the body that the pathogenâs threat still looms, coaxing cells into reinvigorating their defenses and sharpening their coronavirus-detecting skills, and prolonging the duration of protection. Some of that familiarity might ebb with certain variants. But in broad strokes, a post-inoculation infection can be âlike a booster for the vaccine,â Su, of the University of Pennsylvania, said. Itâs not unlike keeping veteran fighters on retainer: After the dust has settled, the battleâs survivors will be on a sharper lookout for the next assault. Thatâs certainly no reason to seek out infection. But should such a mishap occur, thereâs a good chance that âcontinuously training immune cells can be a really good thing,â Nicole Baumgarth, an immunologist at UC Davis, said. (Vaccination, by the way, might mobilize stronger protection than natural infection, and itâs less dangerous to boot.)
We canât control how SARS-CoV-2 evolves. But how disease manifests depends on both host and pathogen; vaccination hands a lot of the control over that narrative back to us. Understanding breakthroughs requires some intimacy with immunology, but also familiarity with the realities of a virus that will be with us long-term, one that we will probably all encounter at some point. The choice isnât about getting vaccinated or getting infected. Itâs about bolstering our defenses so that we are ready to fight an infection from the best position possibleâwith our defensive wits about us, and well-armored bodies in tow.
By Katherine J. Wu (The Atlantic). Illustration by Adam Maida/The Atlantic.