To slow the spread, the US Centers for Disease Control and Prevention (CDC) on July 27 updated its guidance on face masks to recommend that people who are fully vaccinated wear them “in public indoor settings in areas of substantial or high transmission.”
It’s a reversal from the CDC’s May decision to drop its mask mandate for fully vaccinated people in most circumstances—a decision that raised eyebrows among some public health experts. The CDC’s update is based on evidence that “though they happen in only a small proportion of people who are fully vaccinated, some infections do occur among fully vaccinated people,” and that “fully vaccinated people who do become infected with the delta variant can transmit it to others.”
To help Americans figure out whether they should once again wear masks in indoor spaces, the CDC has created a map of all US counties, classified by the level of community transmission of Covid-19, from high to low. It shows that community transmission is highest in the south and the northwest parts of the country, and lowest in the northeast.
For example, in Hamilton County, New York, 81% of the population has received at least one dose of a Covid-19 vaccine, and there have been zero new cases since June 28, while in Comanche County, Oklahoma, 46.4% of the population has gotten at least one vaccine dose, and 176 people there tested positive over the past seven days, a 63% increase from the week prior.