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- V-safe is a vaccine safety monitoring system in which participants receive text messages with health survey links for up to a year after their vaccination. More than 9.2 million people have enrolled.
- The federal government created v-safe to monitor the safety of the COVID-19 vaccines. It’s one of several such tools used by federal health agencies. The resulting data has informed various CDC studies and analyses, including one that says the mRNA vaccines did not show increased risk for miscarriage.
- The surveys take about a minute to complete and ask questions like “How are you feeling today?”
Of the nearly 200 million people who have received at least one dose of a COVID-19 vaccine, more than 9 million have enrolled in a program to share information about their health since getting the shot.
The initiative was created for the COVID-19 vaccines as an addition to the Centers for Disease Control and Prevention’s vaccine safety monitoring system. Known as v-safe, the registry lets inoculated people report their experiences, including serious suspected side effects, directly to the CDC through smartphones, complementing data gathered from clinical trials and other safety monitoring systems.
So how does v-safe strengthen the nation’s existing safety checks and how well is it working?
Some public health experts expressed doubts. But since the tool’s Dec. 13 release, reviews have mostly been positive.
"It's a really good way to make everybody part of the process," said Dr. Kathryn Edwards, founder of the Vanderbilt Vaccine Research Program and principal investigator for the CDC-funded Clinical Immunization Safety Assessment Network.
"There never has been so much scrutiny of vaccines and so much reporting and so much tailored information," she added.
The federal government has various systems to monitor the safety of vaccines as well as other pharmaceutical products once they reach the marketplace. For starters, the Vaccine Adverse Event Reporting System, jointly run by the CDC and Food and Drug Administration, has served since 1990 as a repository for reports on health problems that may be side effects of vaccines. Health care providers are required by federal law to report certain adverse events, but patients, their family members or caregivers can also submit a report online.
VAERS receives tens of thousands of reports each year, which are stripped of personal identifiers and publicly shared in an online database. These reports, which frequently lack details and sometimes contain errors, are not enough to establish a causal relationship between the vaccine and an adverse event, but they offer the federal agencies, scientists and researchers a chance to identify and investigate unusual patterns.
VAERS helped spot unexpected cases of rare blood clots in several people who received the Johnson & Johnson vaccine. After studying the VAERS reports, the CDC listed what experts later identified as thrombosis with thrombocytopenia syndrome as a serious but rare health problem associated with the J&J vaccine.
Then there’s the Vaccine Safety Datalink, which uses electronic health data from nine large health care organizations across the country, including various Kaiser Permanente systems on the West Coast and Harvard Pilgrim Health Care in Massachusetts. According to Minnesota-based HealthPartners, another participating organization, the VSD network looks at data for 3% of the U.S. population, or roughly 12 million people — everything from medical and pharmacy claims to vital records. Analyses are done weekly so signals of adverse events are quickly noted, National Geographic reported.
Launched the day before COVID-19 vaccines were first available to the public, v-safe allows the CDC to monitor people’s health over time.
Some vaccine safety experts have criticized the U.S. for leaning too heavily on a "passive" system that relies on people reporting issues that may or may not be related to the shots, as opposed to "active" surveillance that scans large volumes of electronic health data and compares adverse events in people who receive the vaccine to those who didn’t.
V-safe requires individuals to opt in, with no control group for comparison. But some still view the tool as a step forward.
"It is a little bit more of a proactive monitoring system" than the other mechanisms currently in place, said Andrea Carcelén, an assistant scientist at the International Vaccine Access Center at Johns Hopkins Bloomberg School of Public Health.
Here’s how it works: People register with the v-safe program on their smartphone or computer after receiving their first vaccine dose. The CDC then sends them daily text messages for the first week, and weekly ones for six weeks after that. Additional follow-up texts are sent at the three-, six- and 12-month marks.
Every message includes a link to a brief health survey, always asking: "How are you feeling today?" The first week, participants are asked whether they have experienced symptoms — chills, headache, joint pain or something not listed. They are also asked if they were unable to work or attend school or perform "normal daily activities," or if they sought a physician’s care.
Over time, the check-ins focus more on whether there are new or worsening symptoms or health conditions, and compare participants’ health before and after vaccination. Participants are also asked if they have tested positive for COVID-19 since the previous survey.
CDC scientists then study responses, looking for patterns of problems that go beyond what the clinical trials predicted. And the data may provide a fuller snapshot of vaccine outcomes because it reflects not only reports of side effects but also of people who had no complaints, said Carcelén.
Even as these investigations proceed, people who reported a problem may not ever hear directly from the CDC, and v-safe is not intended to offer medical advice. The CDC requests and reviews medical records, death certificates and autopsy reports only for serious adverse events, said Martha Sharan, a CDC spokesperson. "If a report is a hoax, it is quickly caught," she said.
And what has v-safe shown so far? "The findings in normal, regular people that got the vaccine were pretty reflective of what you saw in the clinical trials," said Vanderbilt’s Edwards. Edwards also served on an independent safety data monitoring committee for the Pfizer-BioNTech vaccine.
Unlike VAERS, v-safe data is not published without context — meaning no one can just sort through the database and interpret the numbers as they please, as many do with VAERS data. It is, however, publicly shared through CDC studies and presentations given during meetings held by the CDC’s independent panel of experts, the Advisory Committee on Immunization Practices.
And like VAERS reports, v-safe data is susceptible to misinterpretation. One post that circulated on social media inaccurately said "3,150 persons were paralyzed," based on an presentation slide from the CDC advisory panel. Reuters debunked the post, saying it is a "misinterpretation of the CDC health events."
Information gleaned from v-safe has been used in several safety analyses, including one focused on adolescents. That analysis, published Aug. 6, found that serious adverse events are rare among adolescents, partly based on v-safe surveys from tens of thousands of people ages 12 to 17. The analysis also found that a minority reported being unable to perform "normal daily activities" the day after receiving a second dose.
V-safe has perhaps been most helpful at providing real-world evidence that the COVID-19 vaccines are safe during pregnancy. This is important because there was little information on how the vaccines affected pregnancy when they were first authorized, said Dr. Dana Meaney-Delman, a member of the CDC’s vaccine task force, in a recent call with clinicians.
Pregnant women were excluded from the initial clinical trials that led to the emergency use authorization of the Pfizer, Moderna and J&J vaccines, and misinformation was rampant..
Because pregnant health care workers got vaccinated and enrolled in v-safe, Meaney-Delman said, there is more evidence that indicates the benefits of getting vaccinated during pregnancy outweigh any potential risks. Following the publication of an analysis that leaned on v-safe’s vaccine pregnancy registry, the CDC recommended on Aug. 11 that people who are pregnant, lactating or trying to get pregnant get vaccinated against COVID-19.
Currently, uptake is low — as of mid-August, 23% of pregnant people ages 18 to 49 are at least partially vaccinated.
More than 9.2 million people have enrolled in v-safe as of Aug. 9, or roughly 5% of the U.S. population who received at least one dose of a COVID-19 vaccine. This seemingly low participation rate is often linked to weak advertising and public education programs about v-safe. Also, a segment of the vaccinated public likely considered it tedious or had privacy concerns. And people who do not have smartphones can’t participate.
This is a significant gap in reporting, says Dr. Matthew Laurens, a vaccine researcher at the University of Maryland School of Medicine. Roughly a quarter of adults who earn below $30,000 per year — or an estimated 16% of U.S. households — say they do not own a smartphone.
People who line up for a vaccine booster — an extra dose beyond the one or two shots indicated for that vaccine — will have another opportunity to sign up for v-safe.
Some v-safe participants said they joined the effort because they wanted to help.
John Beeler, 44, of Atlanta, considered it a "public good." He reported experiencing tinnitus — an ear condition that was part of his medical history — after receiving his first Moderna dose. He was never contacted but said he hopes his report proved helpful and he appreciated being checked on, even if it’s only via automation.
"Dr. Fauci is not reading my response," said Beeler. "But the feeling is there."
Centers for Disease Control and Prevention, Safety of COVID-19 Vaccines, updated Aug. 12, 2021
Centers for Disease Control and Prevention, V-safe After Vaccination Health Checker, updated Aug. 13, 2021
Phone interview with Dr. Kathryn Edwards, founder of the Vanderbilt Vaccine Research Program, Aug. 11, 2021
Centers for Disease Control and Prevention, New CDC Data: COVID-19 Vaccination Safe for Pregnant People, Aug. 11, 2021
Centers for Disease Control and Prevention, COVID-19 Vaccine Reporting Systems, updated Aug. 9, 2021
United States Department of Health and Human Services, About VAERS,
Centers for Disease Control and Prevention, Vaccine Safety Datalink (VSD), reviewed Aug. 24, 2020
Centers for Disease Control and Prevention, COVID-19 Vaccinations in the United States, updated Aug. 15, 2021
The United States Census Bureau, Computer and Internet Use in the United States: 2018, April 21, 2021
Email Interview with Matthew Laurens, a vaccine researcher at the University of Maryland School of Medicine, Aug. 11, 2021
Pew Research Center, "Digital divide persists even as Americans with lower incomes make gains in tech adoption," June 22, 2021
Email interview with Martha Sharan, a CDC spokesperson, Aug. 10, 12, 13
Phone interview with Shireen Shakouri, v-safe participant, Aug. 6, 2021
Phone interview John Beeler, v-safe participant, Aug. 6, 2021
Phone interview with Josh Israel, v-safe participant, Aug. 6, 2021
Phone interview with Andrea Carcelén, an assistant scientist at the Johns Hopkins Bloomberg School of Public Health, Aug. 17
NPR, "Anti-Vaccine Activists Use A Federal Database To Spread Fear About COVID Vaccines," June 14, 2021
Reuters, "Fact check: 3,150 people were not ‘paralyzed’ after receiving COVID-19 vaccine," Jan. 19, 2021
The New England Journal of Medicine, Preliminary Findings of mRNA Covid-19 Vaccine Safety in Pregnant Persons, June 17, 2021
Centers for Disease Control and Prevention, First Month of COVID-19 Vaccine Safety Monitoring — United States, December 14, 2020–January 13, 2021, Feb. 26, 2021
Centers for Disease Control and Prevention, COVID-19 Vaccine Safety in Adolescents Aged 12–17 Years — United States, December 14, 2020–July 16, 2021, Aug. 6, 2021
Phone interview with Joy Onozuka, with the American Tinnitus Association, Aug. 13, 2021
Health Partners, "Expert answers to the top three concerns about COVID-19 vaccine safety,"
National Geographic, "Vaccines are highly unlikely to cause side effects long after getting the shot" July 22, 2021
s say," May 2, 2021
CDC/IDSA COVID 19 Clinician Call, "Additional Vaccine Doses in the Immune Compromised; Plus the Latest on the Delta Variant and Vaccination in Pregnant Women," Aug. 14, 2021
Centers for Disease Control and Prevention, "New CDC Data: COVID-19 Vaccination Safe for Pregnant People," Aug. 11, 2021
Research Square, "Receipt of mRNA COVID-19 vaccines preconception and during pregnancy and risk of self-reported spontaneous abortions, CDC v-safe COVID-19 Vaccine Pregnancy Registry 2020-21" Aug. 9, 2021