If you’re younger-than-or-equal-to GenX, I think you’ll recognize this vibe: My mom and stepfather live in a little California beach town. They’re both over 75, and for the past year they’ve been careful as hell about exposures and risks to avoid getting Covid-19. She’s in good health; he’s not. And now, at last, they both are two weeks out from their second shot of the Pfizer vaccine. So of course, I got the email: “Three people have asked to come visit,” Mom wrote. “I am conflicted and not sure how to handle.”
I don’t mean to put my stuff onto you, but these kinds of questions are only going to start coming faster and furiouser. More than half the old folks in the United States have been vaccinated against Covid-19—65 percent of people 75 years of age or older. That’s great news. It also means that more and more people are trying to figure out what happens next. Earlier this week, news leaked that the Centers for Disease Control and Prevention were going to release long-awaited guidelines for how vaccinated people might behave safely in the interregnum before the New Normal when all of the everybody are vaccinated—call where we live now the New Weirdness, maybe? But then those guidelines got delayed again, and every American is back to figuring it out for themselves. And their parents.
Mom’s specific questions, I realized, might be more broadly informative, if I could figure out how to answer them. The basics: An aunt and uncle want to visit, and they’ve been vaccinated. My stepsister and her mother want to come, and they haven’t been—and they plan to see other people on the trip. And a cousin and her kids want to come. They’ve all had Covid—bad cases, all recovered. Now, Mom and Stepdad haven’t seen any family (aside from one medical-emergency visit from me and my immediates) in over a year. Stepdad would benefit from the contact. “I would much appreciate some guidance,” Mom says.
Heh. Yeah. Wouldn’t we all? A year ago—hell, three months ago—everyone lived on the same attack surface. Our risk profiles weren’t identical, because Covid-19 preferentially kills poor people and people of color for lots of terrible socioeconomic reasons, and because older people and people with certain medical conditions are more likely to get very sick and die of the disease. But basically we all had to follow the same precautions to keep from getting infected and keep from transmitting that infection to others: masks, physical distance, avoid indoor gatherings, keep spaces well-ventilated.
Differential vaccination gives that attack surface a whole new terrain. Vaccinated people live in the hills and the rest of us still live in the flats. So I asked a handful of people who study viruses and sick people what they’d say to my mom—partially so I’d have something smart to say to her, but also to try to understand not just the problem but how to think about it, the specific shape of that risk terrain and blurriness of its edges. The science isn’t settled. The risks aren't well-understood. So the parameters for decisionmaking here are tolerance for risk and uncertainty, of which there is still quite a lot of both.
“They have had both shots, and they still keep pretty much to themselves. The one issue might be that they plan to stop at a friend’s house for two days on the way here.” —Mom
The best news of the past few months is that the three approved Covid-19 vaccines—the two-shot, mRNA-based ones from Pfizer and Moderna and the single-shot, adenovirus-vectored one from Johnson & Johnson—have one thing in common. They’re awesome. In trials, each prevented death and severe disease. But even though those are the endpoints that the vaccine makers tested, they aren’t the only important things to consider. “We actually don’t know whether in real life, at the population level, that efficacy translates into vaccine effectiveness,” says Ana Bento, a disease ecologist at the Indiana University School of Public Health. “While it might protect you against disease, it might not protect you against infection. It’s too soon to actually know that.”
That matters for two reasons. First, it’s still possible that someone who’s been vaccinated could actually get sick—the risk is very slender, but not zero. And second, because unvaccinated people can be infected with Covid-19 and transmit it to others without showing any symptoms, it remains possible that someone vaccinated could also still be, in effect, a carrier.
Now, it seems pretty clear that all the vaccines will stop some infection and transmission, maybe quite a lot. “The data are all pretty consistent with that number being a two-thirds reduction,” says Bob Wachter, chair of the Department of Medicine at UC San Francisco. “Maybe it’s a three-quarter reduction or a 60 percent reduction, but the key thing is it’s a substantial reduction in the probability you will catch it, carry it, feel fine, and spread it to someone else.”
Given all that, my vaccinated aunt and uncle visiting my folks seems like the easiest scenario. Everyone involved is protected against serious illness, and everyone’s at least somewhat protected against getting infected and transmitting it. “I’m confident enough that between my protection as a vaccinated person and the decreased probability that another vaccinated person is going to have it and spread it, when you do the math there the chances that something bad is going to come between vaccinated people are really, really small,” Wachter says.
The risk here is even smaller given that my aunt and uncle have been just as cautious as my mom and stepdad—maybe even if they see someone else on their trip. Risk, in this sense, is additive. “I think it makes sense that two vaccinated households that aren't mixing with other, non-vaccinated households could get together indoors for dinner,” says A. Marm Kilpatrick, an infectious disease researcher at UC Santa Cruz. “That initially sounds risky, but since both households are vaccinated, the risk of anyone getting sick even if someone was infected is much lower. And if neither household is mixing with other people, their risk of being infected to begin with is very low.”
Broadly, vaccinated people don’t have nothing to worry about, but they have far less than the rest of us. They can probably fly on an airplane, if they keep their masks on. Eating indoors at a restaurant? Eh. Maybe not yet. More exposures, more risks for everyone.
Meanwhile, the kind of gathering my mom is pitching here is like having lots of defenses layered together—multiple people with multiple protections against illness and transmission, like the “Swiss cheese model” of risk-reducing non-pharmaceutical interventions, only this time all stacked up and administered in a hypodermic needle. Green light! Dinner like it’s 2019.
“Neither has gotten vaccinated, and they socialize with others.” —Mom
This one has the biggest yikes factor. I told Mom that while she and Stepdad had a massively reduced risk of getting sick themselves, it wasn’t zero. They’re back in mask territory here. “I personally still feel like wearing masks is very reasonable,” says Grace Lee, an infectious disease physician at Stanford Children’s Health and member of the CDC’s Advisory Committee on Immunization Practices. “My hope is, they will be safer if they continue to mask and use good hand hygiene and control what they can, but their risks are mitigated a lot by getting vaccinated.”
Mom and Stepdad don’t want to get sick, and—improbable though it may be—they don’t want to get Stepsis and her mom sick either, or end up as links in some longer epidemiological chain. My rule in this pandemic has been: Don’t become the main character in a CDC case study. It’s unlikely, but still possible, that vaccinated people could be an infectious bridge between unvaccinated households. Kilpatrick’s rough calculations of how much the vaccines reduce infection and transmission are an optimistic 80-to-90 percent, but that’s still not perfect. “It’s much safer than when they weren't vaccinated, but not high enough to be low risk,” he says.
But here’s where personal risk tolerance comes into play. Bento’s research on pandemic behavior has found that people fall along a spectrum from being completely risk-averse to being “risk-happy,” YOLOing their way into viral legend. Vaccination makes that risk-taking more complex, because it’s less about you and more about others. Even if the vaccines work as advertised, “if you get infected, you’re asymptomatic and you don’t incur any sort of loss,” Bento says. “It becomes really more about protecting people around you.”
Still, though. Stepdad's health status is such that seeing his daughter and her mother might help him a lot, or at least make him feel better for a while. That’s not nothing—enough of something, in fact, to build into the risk-benefit matrix.
I suggested not having these visitors stay overnight at the house—maybe a hotel, if they can all make the finances work—and having a nice take-out lunch outside on the driveway, or a walk along the water. California weather is a real advantage here.
“They all had Covid, were down for a month, with one also contracting pneumonia. Don’t know if they got the vaccine.” —Mom
Here’s where Mom and Stepdad’s own tolerance for risk—and perception of the benefit of social contact—will get taxed the most. Nobody really knows the answer, because nobody fully understands how the human immune system deals with Covid-19, and what happens over time, after recovery. In one recent study, researchers took a kind of immunological census of more than 200 people who’d had Covid-19, testing their blood over eight months for its “immune memory.” The scientists looked for antibodies, memory B cells, CD8+ T cells, and CD4+ T cells, all fighting SARS-CoV-2. These “correlates of immunity” aren’t completely defined for Covid-19, but here, the news was good. About 95 percent of the people the researchers tested still had immune memory eight months after recovering from Covid.
On the flip side, that means about 5 percent of people didn’t. And nobody knows which people that’ll be, or why. A study of how people who’d been infected with SARS-CoV-2 responded to the mRNA-based vaccines—a preprint, so not yet peer-reviewed—showed that previously-infected people had increased immune responses similar to those of people who hadn’t yet had the disease. They already had some immunity, but the vaccine gave them more. That’s good news, but it also shows that natural immunity is somehow different from the vaccine-induced kind. Again, no one’s sure exactly how. This problem isn’t specific to Covid-19, by the way; people have the same uncertainties about seasonal influenza and pertussis, the disease Bento knows best. “For all the years I’ve been working on whooping cough, pertussis, that is still the number one question—what are the correlates of protection?” she says. “This was a disease that, 20 years ago, was very close to being eradicated. It’s been studied for decades. And we are none the wiser still.”
That means some caution is still necessary between vaccinated and recovered people. But no one knows how much. “We don’t know how much of an immune response they mounted, so I perhaps would be a little bit more careful. Maybe a backyard barbecue,” Bento says. “I would wait a bit longer, until we have a better sense of when immunity wanes and what are the real correlates of protection in terms of antibody levels.”
That’s pretty much where Wachter’s head was, too. “I’m living that now, in visiting my parents in Florida. And I live it at home because I’m vaccinated, and my wife, who’s a journalist, is not,” he says. “The way I deal with it at home is, I have now become more comfortable doing a few things I would not have done, because I feel like I’m safe, I’m not going to die.” Wachter got a haircut (while wearing an N95 mask). He flew to Florida—masked, only taking it off briefly to wolf down half a sandwich, 20 minutes after other passengers had mostly put their masks back on. And with his parents, mom (vaccinated) got a hug, and dad (unvaccinated at that point) got a fist-bump. Wachter talked to him from a distance, with a fan blowing away from his father.
But Wachter didn’t wear a mask. Because, you know, his dad is 90, and bedbound, and … it’s his dad. “The emotional toll of all of this is very real, and we’re all humans,” Wachter says. “Approaching this like airport security, where you can’t tolerate even a one-in-a-million chance of blowing it, is not realistic.”
So that’s what I told my mom, too. That’s the shape of the problem, the known knowns and the known unknowns. Stepdad’s and Mom’s emotional wellbeing factors into the risk; if that means that they have my stepsister and her mother inside (with all the windows open, an air purifier running, and staying far apart or masked), because that’ll make Stepdad feel better for a few hours, that’s a pretty good bet, I said.
Mom got it. She said thanks. Over the phone, I heard her exhale hard.
Then she asked when I was going to bring her grandchildren to visit.
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