From the Center for Disease Control website:

Considerations for Small Gatherings of Family and FriendsCelebrating virtually or with members of your own household (who are consistently taking measures to reduce the spread of COVID-19) poses the lowest risk for spread. Your household is anyone who currently lives and shares common spaces in your housing unit (such as your house or apartment). This can include family members, as well as roommates or people who are unrelated to you. People who do not currently live in your housing unit, such as college students who are returning home from school for the holidays, should be considered part of different households. In-person gatherings that bring together family members or friends from different households, including college students returning home, pose varying levels of risk.

Organizers and attendees of larger events should consider the risk of virus spread based on event size (number of attendees and other factors) and take steps to reduce the possibility of infection, as outlined in the Considerations for Events and Gatherings.

There are several factors that contribute to the risk of getting and spreading COVID-19 at small in-person gatherings. In combination, these factors will create various amounts of risk: Click to read more.