We track COVID-19 variants in California to control the spread of the disease.
On this page you’ll find:
- What a variant is
- Variants we’re tracking
- Vaccine effectiveness against variants
- Variants in California
What a variant is
Viruses change through mutations that create new strains of virus over time. This is a normal process that happens with most viruses. We call these strains variants.
Some variants rise and then disappear. Other variants become common. Most variants do not have a meaningful impact.
Variants we’re tracking
Variants of concern
Variants of concern are likely have one or more of the following features:
- More contagious
- Likely to cause more severe symptoms
- Resistant to treatment
- More resistant to vaccines
Variants being monitored
Variants being monitored are seen at low levels or no longer detected. They do not pose a significant or immediate risk to the public. They are likely to have one or more of the following features:
- Potential or known effect on treatment
- More severe symptoms
- Increased transmission
California follows the CDC’s variant classifications and definitions.
Vaccine effectiveness against variants
We are working to better understand how these variants respond to vaccination. Vaccines provide valuable protection against variants circulating in California.
COVID-19 vaccines are effective against variants of the virus currently circulating in the United States, including the Delta variant. We are closely following evolving information about the ability of COVID-19 vaccines to protect against variants.
Variants in California
We genetically sequence a sample of positive COVID-19 tests to determine which variant they are. This helps us understand which variants are circulating in California.
[Variant percentage chart]