California vs CDC COVID-19 colored tiers

The new CDC guidance on reopening schools has created some confusion, especially with their colored tiers.

If community transmission is high, students and staff are more likely to come to school while infectious, and COVID-19 can spread more easily in schools. The association between COVID-19 incidence and transmission in school settings and levels of community transmission underscores the importance of controlling disease spread in the community to protect teachers, staff, and students in schools. This means that all community members, students, families, teachers, and school staff should take actions to protect themselves and others where they live, work, learn, and play. In short, success in preventing the introduction and subsequent transmission of SARS-CoV-2 in schools is connected to and facilitated by preventing transmission in communities.

Transitioning from CDC’s Indicators for Dynamic School Decision-Making (released September 15, 2020) to CDC’s Operational Strategy for K-12 Schools through Phased Mitigation (released February 12, 2021) to Reduce COVID-19

The CDC categories are based on a case rate per 100,000 people over 7 days.

The CA tiers are a 7 day average case rate per 100,000 people. So they add up 7 days of cases and then divide by 7 to get an average.

Although not an exact translation, a simple way to estimate which CDC category we fall into is to multiple the CA case rate by 7.

The California Tier thresholds have changed multiple times, including immediately after I had updated this page with the second version. The most recent change in tier thresholds was the result of the state reaching the goal for administering 4M doses in low income areas. Below is the latest comparison of the California Tiers and the CDC Categories. This will likely be the last revision before CA ends their tiers system, which is slated for June 15 unless we see another surge in cases and/or hospitalizations

The next comparison is based on the updated tier thresholds that went into effect in California after the state met their goal of administering 2M doses in low income areas. Once the metric was met, the range for the red tier was relaxed to include up to 10 cases per 100k for the 7 day average case rate.

Below is the original comparison after the updated CDC guidelines came out early in 2021.

For example as of February 14, 2021, the San Diego County COVID-19 Triggers dashboard shows a case rate of 34.2. That is, our daily average case rate is 34.2 people per 100,000.

34.2 x 7 = 239.4. Which puts us in the CDC’s red category.

You’ll notice that originally the CA purple tier was basically both the orange and red CDC categories. By the time CA hit the red tier, we would have be in the CDC’s yellow category. However, due to the change in tier thresholds that went into effect in March 2021, California’s red tier now spans parts of the CDC yellow and orange categories.

See this color-coded map of San Diego County for a regional breakdown of where we fall in the CDC category system.