If you got a phone call from the CDC, it’s most likely because your phone number was randomly selected for a national health survey. The CDC runs several large telephone surveys every year, and millions of phone numbers are dialed to collect data on everything from vaccination rates to chronic disease. Less commonly, the CDC or a local health department may call because you were potentially exposed to an infectious disease during an outbreak investigation.
Health Surveys: The Most Common Reason
The CDC conducts ongoing telephone surveys to track the health of the U.S. population. Your number wasn’t pulled from a personal database or flagged for any reason. Cell phone numbers are randomly generated and dialed, meaning you were selected the same way someone wins (or loses) a lottery. The two surveys most likely to land in your voicemail are the Behavioral Risk Factor Surveillance System (BRFSS) and the National Immunization Survey (NIS).
The BRFSS is the nation’s largest health-related phone survey. It collects state-level data on risk behaviors like smoking and physical inactivity, chronic conditions like diabetes and heart disease, and use of preventive services like cancer screenings. It also tracks emerging issues such as flu-like illness and vaccine availability. If the caller asks about your exercise habits, diet, or whether you’ve had a recent checkup, this is likely the survey you’re in.
The NIS focuses specifically on childhood and teen vaccination. Randomly selected cell phone numbers are called to find households with age-eligible children. If you have kids, the interviewer will ask about their vaccination history and request permission to contact their doctor’s office for records. They won’t ask you to read off vaccination dates yourself. Instead, a paper questionnaire gets mailed to the provider to collect that information directly.
Outbreak and Exposure Notifications
The other reason the CDC or a public health department might call is contact tracing during a disease outbreak. This became widely known during COVID-19, but the practice applies to other infectious diseases as well. A contact tracer’s goal is to let you know you may have been exposed, check on your health and vaccination status, and help you access testing or care if needed. They may also ask you to monitor yourself for symptoms.
These calls tend to be more direct and specific. The caller will reference a particular disease and a possible exposure event, rather than asking broad questions about your lifestyle or health habits. If you weren’t recently near a known outbreak or in close contact with someone diagnosed with a communicable disease, this type of call is unlikely.
Who’s Actually on the Line
The CDC doesn’t always make these calls directly. It contracts with private research organizations to handle the phone work. NORC at the University of Chicago administers the National Immunization Surveys. ICF Incorporated handles data coordination for other CDC programs under a contract worth $14.3 million running through 2026. So the voice on the other end may identify themselves as calling from one of these organizations on behalf of the CDC, which is legitimate.
Your caller ID may show “CDC NATL IMMUN” with a 404 area code (Atlanta, where the CDC is headquartered). The specific numbers used for NIS calls include 404-809-2644, 404-809-2195, 404-806-4810, 404-806-4811, and 404-806-4812. Older calls may have displayed “NORC UCHICAGO” with a Chicago number, but the CDC switched all outgoing NIS calls to the “CDC NATL IMMUN” display starting in 2018 after testing showed it helped people recognize the call as legitimate.
How to Verify the Call Is Real
If you missed the call or you’re unsure whether it was genuine, call NORC directly at 1-877-220-4805. Representatives are typically available from 9 a.m. to 9 p.m. in your time zone. Call from the same phone that received the original call so they can look up your number in their system.
A real CDC survey call will never ask for your Social Security number, bank account information, credit card numbers, or any form of payment. The surveys collect health data only. If a caller claiming to be from the CDC asks for financial information, requests money, or pressures you to act immediately on a supposed health threat, that’s a scam. Hang up.
Participation Is Voluntary
You’re not required to answer a CDC survey. These calls are voluntary, and there’s no penalty for declining or hanging up. That said, the data collected through these surveys shapes public health policy at the state and national level, from how vaccination campaigns are targeted to where chronic disease prevention funding goes. If you have 15 to 30 minutes, your answers contribute to a dataset that health agencies rely on to make decisions affecting millions of people. But the choice is entirely yours.