Important: VAERS reports alone cannot determine if a vaccine caused an adverse event. Reports may contain incomplete, inaccurate, or unverified information. Correlation does not equal causation.
More than 677,000,000 COVID-19 vaccine doses have been administered in the United States since December 2020. With over five years of real-world safety data now available, here is what the monitoring systems have found — confirmed signals, studied concerns, and what long-term follow-up reveals.
The COVID-19 vaccination campaign is the largest and most closely monitored in U.S. history. From the first Emergency Use Authorization in December 2020 through mid-2026, approximately 677,000,000 doses of COVID-19 vaccine have been administered — spanning the original two-dose primary series, boosters, and updated formulations targeting newer variants. At peak rollout in spring 2021, more than 3 million doses were being given daily.
This massive scale means that the safety surveillance systems have more data than for any other vaccine in history. What follows is a review of what those systems have found over five-plus years of monitoring.
V-safe was a CDC smartphone-based active surveillance tool where vaccinated people could voluntarily report health status after each dose. Over 10,200,000 people enrolled — roughly one in every 20 vaccinated Americans — making it the largest active vaccine safety surveillance effort ever conducted.
Key findings from V-safe data:
V-safe was decommissioned in 2023, but the data has been made publicly available and continues to inform safety analyses.
The VSD is a collaboration between the CDC and nine integrated health care organizations covering approximately 12 million members. Unlike VAERS, the VSD links vaccination records to electronic health records, enabling researchers to compare rates of specific outcomes in vaccinated vs. unvaccinated populations — the gold standard for detecting true safety signals.
Over five years, VSD studies have:
As of mid-2026, VAERS has received approximately 724,000 reports following COVID-19 vaccination. This is by far the largest body of reports for any single vaccine in VAERS history — reflecting both the massive number of doses administered and heightened public awareness of the reporting system during the pandemic.
Important context for interpreting this number: VAERS is a passive reporting system where anyone can file a report. A report does not mean the vaccine caused the event. During COVID-19, reporting rates were dramatically higher than for other vaccines due to public awareness, media attention, legal requirements for healthcare providers to report certain events, and deliberate efforts by some groups to encourage reporting. See our denominator problem analysis for why raw VAERS counts require careful interpretation.
Of the 724,000 reports, approximately 8% were classified as serious (involving hospitalization, life-threatening events, permanent disability, or death). You can explore the full breakdown in our serious outcomes analysis.
Myocarditis (inflammation of the heart muscle) is the most significant confirmed safety signal for mRNA COVID-19 vaccines. First identified through VAERS in mid-2021 and subsequently confirmed by VSD, international databases, and clinical studies, the signal has been extensively characterized:
For a deeper dive into myocarditis data, see our myocarditis overview page with VAERS-specific analysis.
Thrombosis with thrombocytopenia syndrome (TTS) was a rare but serious condition associated specifically with the Johnson & Johnson / Janssen adenoviral vector COVID-19 vaccine. Approximately 60 confirmed cases were identified in the U.S. out of about 19 million doses administered, with a case fatality rate of roughly 15%.
TTS involved unusual blood clots (often cerebral venous sinus thrombosis) combined with low platelet counts, primarily affecting women under 50 within two weeks of vaccination. The mechanism — antibody-mediated platelet activation similar to heparin-induced thrombocytopenia — was identified relatively quickly, enabling targeted clinical management.
With mRNA alternatives widely available and the TTS risk unique to the adenoviral platform, the J&J vaccine was withdrawn from the U.S. market in June 2023. This represents the safety monitoring system working as intended: a rare signal was detected, characterized, and acted upon.
One of the most important long-term safety questions is whether COVID-19 vaccination affects overall mortality. Multiple large studies have examined this:
The U.S. is not the only country monitoring COVID-19 vaccine safety. International databases provide critical corroborating data:
COVID-19 vaccine efficacy against infection wanes substantially within 4–6 months, though protection against severe disease and hospitalization has proven more durable, lasting 6–12 months or longer. This waning has driven the shift to annual updated boosters, similar to seasonal flu vaccination.
Safety data for booster doses (third, fourth, and updated formulations) has generally been consistent with the primary series, with somewhat lower rates of systemic reactions reported after subsequent doses. The myocarditis risk appears lower with boosters than with the second primary dose, based on VSD and international data.
COVID-19 vaccines introduced mRNA technology to mass human use for the first time. Five years later, the platform has a substantial safety track record:
Five years of monitoring — across multiple independent surveillance systems, in dozens of countries, covering hundreds of millions of vaccinated people — have produced a clearer picture of COVID-19 vaccine safety than for any vaccine in history. The confirmed safety signals (myocarditis, TTS) were detected, characterized, and responded to. Large population studies have not shown excess mortality attributable to vaccination. The data does not support concerns about hidden or delayed long-term effects, though ongoing monitoring remains appropriate.
For those exploring VAERS data on their own, we strongly recommend understanding the reporting bias, denominator problem, and who files VAERS reports — context that is essential for accurate interpretation.