Somerville has asked its residents not to trick-or-treat:

Mayor Joseph A. Curtatone and the Somerville Board of Health announced Halloween guidance and related updates today. They strongly urge all community members to forgo trick-or-treating in favor of lower-risk activities as defined by the Centers for Disease Control such as at-home activities and holiday crafts.
   —somervillema.gov

They link to MA and CDC guidelines.

I have generally supported Somerville's cautious approach, closing more quickly and opening more slowly than surrounding towns, keeping schools remote until we can make sure we have sufficient ventilation, organizing outdoor enrichment activities for students, etc. But I don't understand how any town that allows indoor dining can categorize trick-or-treating as impermissibly high risk?

At this stage in the pandemic, we know that transmission primarily happens through shared air, and outdoor activities are far safer than indoor ones. Especially indoor ones where people are, as in restaurants, generally unmasked and talking. Traditional trick-or-treating, where everyone rings the same doorbells, frequents centralized trick-or-treating corridors, gets quite close to each other, and reaches into the same bowls of candy, I agree is risky. The core experience of trick-or-treating, however, is walking around outside in costumes, going to neighbors' houses, and collecting candy. This can be done with very low risk:

• Houses that want to participate should plan socially distanced distribution. Participation is even more optional than usual.
• Trick-or-treat within walking distance of your house.
• Don't go anywhere where you won't be able to social distance.
• Set expectations with your kids about this being more of a search than usual, and clarify there will be less candy.
• Only acquire candy if you're able to do it while keeping distance.
• Wear a face mask, not just a Halloween mask.
• Wait to eat until you're home.

Our fall and winter holidays and traditions are full of gathering indoors with food and song. Trick-or-treating is a rare exception, and we should make the most of it.

I'm planning to take the kids out tomorrow night, and I think if we're thoughtful about what we need to do differently it won't be any more risky than our usual evening walks around the neighborhood.