This matters for two reasons. First, there is always the possibility that a person who has been vaccinated will actually get sick – the risk is very small, but not zero. And second, because unvaccinated people can become infected with Covid-19 and pass it on to others without showing any symptoms, it remains possible that a vaccinated person could also be, in fact, a carrier.
Now it seems pretty clear that all vaccines will stop a few infection and transmission, possibly a lot. “The data is all pretty consistent, with that number being a reduction of two-thirds,” says Bob Wachter, director of the UC San Francisco department of medicine. “It might be a three-quarters or 60 percent reduction, but the bottom line is a substantial reduction in the likelihood that you will catch it, wear it, feel good, and pass it on to someone else.
Considering all of this, my vaccinated aunt and uncle visiting my parents seems like the easiest scenario. Everyone involved is protected against serious illness, and everyone is at least somewhat protected against infection and transmission. “I’m pretty confident that between my protection as a person vaccinated and the reduced likelihood of another vaccinated person suffering and spreading it, when you do the math, it’s really, really small,” Wachter says.
The risk here is even smaller given that my aunt and uncle have been just as careful as my mom and stepdad – maybe even if they see someone else traveling. The risk, in this sense, is additive. “I think it makes sense that two vaccinated households that don’t mix with other unvaccinated households can get together indoors for dinner,” says A. Marm Kilpatrick, infectious disease researcher at UC Santa Cruz. “It sounds risky at first, but since both households are vaccinated, the risk of someone getting sick even if someone has been infected is much lower. And if none of the households mix with other people, their risk of getting infected initially is very low. “
In general, people who have been vaccinated do not have nothing to worry about, but they have a lot less of it than the rest of us. They can probably fly in a plane, if they keep their masks. Eat inside in a restaurant? Hey. Maybe not yet. No more exposures, no more risks for everyone.
Meanwhile, the kind of gathering my mom holds here is like having a lot of stacked tusks – several people with multiple protections against disease and transmission, like the “Swiss cheese patternNon-pharmaceutical risk-reducing interventions, but this time all stacked and delivered through a hypodermic needle. Green light! Dinner as in 2019.
Scenario two: the stepsister and the mother
“Neither has been vaccinated and they socialize with the others.” -Mom
This one has the biggest yikes factor. I told mom that while she and her stepdad had a dramatically reduced risk of getting sick on their own, it wasn’t bad. They are back in hidden territory here. “Personally, I always feel like wearing masks is very reasonable,” says Grace Lee, an infectious disease physician at Stanford Children’s Health and a member of the CDC’s Advisory Committee on Immunization Practices. “I hope they will be safer if they continue to mask themselves and use good hand hygiene and control what they can, but their risks are greatly mitigated by getting the vaccine.”
Mom and stepdad don’t want to get sick, and – unlikely as it is – they don’t want Stepsis and her mother to be sick either, or to end up as links in a longer epidemiological chain. My rule in this pandemic has been: don’t become the main character in a CDC case study. It is unlikely, but still possible, that vaccinated people could be an infectious bridge between unvaccinated households. Kilpatrick’s rough calculations of how vaccines reduce infection and transmission are 80 to 90 percent optimistic, but it’s still not perfect. “It’s much safer than when they weren’t vaccinated, but not high enough to be low risk,” he says.