evidence: According to Piltch-Loeb, exactly how much of a threat Cousin Paula poses to her vaccinated friends and family depends on a few factors: her behavior prior to attending the event, the precautions that the entire group takes, and where she’s coming from. (The CDC still recommends that unvaccinated Americans not travel until they are fully vaccinated.) If Paula has tested negative before the gathering and lives in a community with relatively low transmission, the other attendees won’t be as significant, Piltch-Loeb said. But keep in mind that the CDC currently classifies transmission as substantial or high in more than 90 percent of U.S. counties. [...] Even if they’re relatively safe in a room full of vaccinated grown-ups, unvaccinated kids might pose some danger to those around them: Studies have shown that children can infect others in their household, as well as in schools and other group settings. For this reason, Dowd recommends limiting the amount of time that unvaccinated kids spend in close proximity to their more vulnerable loved ones, such as their grandparents.