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.
Women file 59% of all VAERS reports — nearly twice as many as men. Why?
The gender gap in VAERS reporting is not unique — it's consistent with broader patterns in healthcare utilization and adverse drug reaction reporting worldwide. Several factors contribute:
The immune response difference between men and women is well-documented in immunology research. Women generally produce stronger antibody responses to vaccines, which is beneficial for protection but can also lead to more frequent and pronounced side effects. This is driven by several biological factors:
The gender gap in VAERS reporting has remained remarkably stable through 2026. Even as COVID-19 booster campaigns wound down and reporting returned closer to pre-pandemic baselines, women continued to file the majority of reports. For the 2025-2026 flu season vaccines, women accounted for approximately 62% of adverse event reports — slightly higher than the overall historical average, consistent with higher flu vaccination rates among women.
The new RSV vaccines authorized in 2023-2024 for older adults and pregnant women added a notable data point: maternal RSV vaccination reports were almost exclusively filed by women, as expected, but the gender split for the 60+ population receiving RSV vaccines was closer to 55/45 — narrower than most other vaccine categories.
While the overall gender gap reflects reporting behavior, some safety signals are genuinely gender-specific. The most prominent example is myocarditis after mRNA COVID-19 vaccines, which was observed predominantly in young males (ages 16-24) after the second dose. This signal was not about reporting behavior — it reflected a real biological difference in how young male hearts responded to the vaccine.
Conversely, thrombosis with thrombocytopenia syndrome (TTS) associated with the J&J COVID-19 vaccine was observed more frequently in women, particularly those ages 18-49. These gender-specific patterns underscore the importance of analyzing VAERS data by sex rather than treating all reports as homogeneous.
While women file more reports overall, the rate of serious outcomes (deaths, hospitalizations) per report tends to be similar across genders. This suggests the gender gap is primarily in reporting behavior, not in the severity of adverse events experienced.
The 172,154 reports with unknown gender (9%) represent a significant data limitation. Many older reports and manufacturer-submitted reports do not include gender information.
Understanding gender disparities in VAERS reporting has practical implications for safety surveillance. When evaluating potential safety signals, analysts must account for the baseline gender imbalance in reporting to avoid false signals. A symptom that appears to affect women disproportionately may simply reflect the higher female reporting rate rather than a genuine gender-specific risk.
The FDA has increasingly recognized the importance of sex-stratified analysis in drug and vaccine safety. Clinical trials now routinely report outcomes by sex, and post-market surveillance systems like VAERS benefit from the same approach. As AI-driven analysis tools are developed for VAERS data in 2026, incorporating gender as a key variable will be essential for accurate signal detection.
Women file approximately 59% of all VAERS reports due to a combination of factors: higher healthcare utilization rates, stronger immune responses to vaccines (leading to more noticeable side effects), greater likelihood of reporting adverse drug reactions across all medication categories, pregnancy-related reporting, and occupational exposure as the majority of healthcare workers.
No. The gender gap primarily reflects reporting behavior differences, not different safety profiles. When adjusted for the number of doses received and healthcare engagement patterns, the rate of serious outcomes (deaths, hospitalizations) per report is similar across genders.
A significant portion of VAERS reports — typically around 7-10% — have unknown gender. This is because many older reports and manufacturer-submitted reports do not include gender information, representing a data limitation in the system.
While women file more reports overall, the rate of serious outcomes (deaths, hospitalizations) per report is similar across genders. However, specific conditions like myocarditis after mRNA COVID vaccines were observed more frequently in young males, showing that some safety signals are gender-specific.
As VAERS reporting normalizes following the COVID-19 pandemic surge, the data landscape for gender patterns in adverse event reporting is shifting. Annual VAERS reports in 2025-2026 have returned to the 35,000-45,000 range typical of the pre-pandemic era (2015-2019), making year-over-year comparisons more meaningful again.
The HHS administration has signaled increased focus on vaccine safety data analysis, including the development of AI-powered tools for pattern detection in VAERS reports. While these tools are still under development, they represent a potential evolution in how adverse event data is analyzed and interpreted.
New vaccines entering the market — including RSV vaccines for older adults and pregnant women, updated COVID-19 formulations, and potential H5N1 avian flu vaccines — continue to add new data streams to VAERS. Each new vaccine type provides additional context for understanding gender patterns in adverse event reporting across the full spectrum of vaccine safety surveillance.
This analysis is based entirely on VAERS passive surveillance data, which carries important limitations that must be understood:
For these reasons, VAERS data is best used for signal detection — identifying potential safety concerns that warrant further investigation — rather than for definitive risk assessment. When VAERS surfaces a potential signal, it is investigated using more rigorous systems like the Vaccine Safety Datalink (VSD) and controlled epidemiological studies.
All data on VaccineWatch comes from the official VAERS public-use datasets published by the CDC and FDA. Our current dataset covers reports from 1990 through early 2026. We process the raw data without filtering or editorializing — every metric is a transparent aggregation of official government data.
As VAERS reporting normalizes following the COVID-19 pandemic surge, the data landscape for gender patterns in adverse event reporting is shifting. Annual VAERS reports in 2025-2026 have returned to the 35,000-45,000 range typical of the pre-pandemic era (2015-2019), making year-over-year comparisons more meaningful again.
The HHS administration has signaled increased focus on vaccine safety data analysis, including the development of AI-powered tools for pattern detection in VAERS reports. While these tools are still under development, they represent a potential evolution in how adverse event data is analyzed and interpreted.
New vaccines entering the market — including RSV vaccines for older adults and pregnant women, updated COVID-19 formulations, and potential H5N1 avian flu vaccines — continue to add new data streams to VAERS. Each new vaccine type provides additional context for understanding gender patterns in adverse event reporting across the full spectrum of vaccine safety surveillance.
This analysis is based entirely on VAERS passive surveillance data, which carries important limitations that must be understood:
For these reasons, VAERS data is best used for signal detection — identifying potential safety concerns that warrant further investigation — rather than for definitive risk assessment. When VAERS surfaces a potential signal, it is investigated using more rigorous systems like the Vaccine Safety Datalink (VSD) and controlled epidemiological studies.
All data on VaccineWatch comes from the official VAERS public-use datasets published by the CDC and FDA. Our current dataset covers reports from 1990 through early 2026. We process the raw data without filtering or editorializing — every metric is a transparent aggregation of official government data.