Prevention
Last updated: 12/23/2022
There are many tools to protect against COVID-19 and one of the most important is knowledge. You are less likely to get sick when you combine tools, such as getting vaccinated and boosted, wearing a well-fitted mask indoors and avoiding places where COVID-19 spreads more easily.
There’s no way to know how COVID-19 will affect you. Some people may suffer from long COVID (also known as post-COVID conditions) which includes a wide range of ongoing or new health problems and symptoms that can be difficult to explain, manage or treat. The best way to avoid long COVID-19 is to avoid infection, including getting vaccinated and staying up to date with boosters. Learn more about long COVID.

COVID-19 Spreads More Easily in Some Places
COVID-19 is more likely to spread in places:
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Where people are not vaccinated
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Where people are not wearing masks
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Where it’s crowded and people are close to each other
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With poor airflow, such as indoor locations
To lower your chance of getting sick, choose to spend time in places where COVID-19 is less likely to spread:
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Places where people are fully vaccinated
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Places where people are wearing masks
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Places that are not crowded
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Outdoor places
CDC Community Level of Spread
Mask Recommendations and Requirements
LOW
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People at lower risk for severe illness: wear a mask based on their personal preference
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People at higher risk for severe illness: consider wearing a mask in crowded, indoor public places
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Specific high-risk settings: wear a mask based on personal preference
MEDIUM
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People at lower risk for severe illness: consider wearing a mask in crowded, indoor public places
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People at higher risk for severe illness: wearing a mask in crowded, indoor public places is recommended
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Specific high-risk settings: masks are required
HIGH
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People at lower risk for severe illness: wearing a mask in crowded, indoor public places is recommended
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People at higher risk for severe illness: wearing a mask in crowded, indoor public places is strongly recommended
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Specific high-risk settings: masks are required
Get Vaccinated and Stay Up-To-Date on Vaccination
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Vaccines are safe and effective at preventing serious illness, hospitalization and death from COVID-19
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Everyone ages 6 months and older should get vaccinated and an Omicron booster
Wear a Mask
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Wearing a mask is an easy way to help stop your respiratory droplets from reaching others and to avoid breathing in droplets from others
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The State of California requires everyone to wear masks in:
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Healthcare settings
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Long-term care and adult senior care settings
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When levels of COVID-19 infections are higher, depending on CDC’s COVID-19 community levels, masks are:
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Recommended for everyone in crowded, indoor places
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Required in specific high-risk settings by the State, including homeless shelters, emergency shelters, cooling and heating centers, State and local correctional facilities and detention centers
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Upgrade Your Mask
Not all masks provide the same protection. Wear a mask with the best fit, protection and comfort for you. No matter which mask you choose, make sure it fits well with no gaps.
Best
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N95 (also best for wildfire smoke)
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Choose a size and model that fits your face and has no gaps
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If you wear an N95 respirator, you should not wear an additional face covering over or under the respirator, as it can interfere with the seal to the face
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Better
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KF94
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KN95
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Double mask
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Wear two masks (disposable mask underneath AND cloth mask on top)
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Good
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Surgical mask
Fair
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Cloth mask
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It should fit snugly and have at least three layers
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A cloth mask is better than no mask
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Good Indoor Ventilation or Be Outside
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Good indoor ventilation can reduce the spread of COVID-19, especially in crowded places
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To improve air flow, open windows and doors, run heating and air systems, and use portable air cleaners
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If you can’t improve ventilation, being outdoors is safer than indoors
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Improving Indoor Air Quality Best Practices, Environmental Protection Agency (EPA)