Both shots together are as safe as one alone
In one of the largest real-world safety studies of its kind, researchers examining the medical records of 2.5 million veterans found no meaningful increase in serious adverse events when flu and COVID vaccines were administered on the same day. The work, published in late June 2026 and drawing on three years of data from the VA health system, offers the kind of population-scale reassurance that small clinical trials cannot provide. At a moment when both viruses continue to exact a measurable toll on human life, the finding quietly expands the space in which convenience and caution can coexist.
- With COVID-19 still claiming tens of thousands of American lives each year and flu a perennial threat, the question of whether two vaccines can safely share a single appointment carries genuine stakes for millions of older and vulnerable adults.
- Clinicians and patients have long faced an uneasy trade-off: the convenience of one visit versus uncertainty about whether combining shots might amplify rare but serious side effects like blood clots, cardiac events, or neurological complications.
- Researchers at the VA St. Louis Clinical Epidemiology Center tracked 46 distinct adverse outcomes over 90 days across more than 705,000 people who received both vaccines simultaneously, comparing them against 1.8 million who received only the flu shot.
- Across all three COVID vaccine iterations studied between 2022 and 2025, not a single tracked outcome showed a statistically significant increase in risk among those who received both vaccines on the same day.
- The findings land as actionable guidance: health systems can now point to large-scale real-world evidence when designing vaccination campaigns, and individual patients can weigh convenience against risk with considerably more confidence.
A major new study from the Veterans Affairs health system has found no evidence that receiving flu and COVID vaccines simultaneously raises the risk of serious side effects — a conclusion drawn from the records of 2.5 million adults and published in the Annals of Internal Medicine on June 30, 2026.
Researchers compared roughly 1.8 million patients who received only the flu shot against more than 705,000 who got both vaccines in a single visit. Over three years spanning three different COVID vaccine formulations, the team monitored 46 adverse outcomes — including cardiovascular events, blood clots, neurological disorders, and immune-mediated complications — in the 90 days following vaccination. None showed a statistically significant increase in risk among those who received both shots together.
The team, based at the VA St. Louis Clinical Epidemiology Center, noted that their findings "support the short-term safety of coadministration in older adults" and could inform both policy decisions and individual conversations between patients and their doctors. For anyone weighing whether to schedule two shots on the same day or space them apart, the data offers a clear answer: convenience need not come at the cost of safety.
The stakes are not abstract. Between October 2023 and September 2024, COVID-19 alone accounted for an estimated 879,000 hospitalizations and 101,000 deaths in the United States. Flu remains a persistent burden alongside it. The ability to address both threats in a single medical visit could meaningfully reduce barriers to immunization — particularly for older adults, who stand to benefit most. What distinguishes this study is its grounding in what actually happened to millions of real patients, rather than the controlled conditions of a pre-approval trial, giving its conclusions a weight that smaller studies cannot match.
A sweeping review of medical records from the Veterans Affairs health system has found no evidence that receiving flu and COVID vaccines on the same day increases the risk of serious side effects. The study, published in the Annals of Internal Medicine on June 30, 2026, examined data from 2.5 million adults across the VA network, making it one of the largest real-world safety assessments of simultaneous vaccination ever conducted.
Researchers compared two groups: roughly 1.8 million patients who received only the flu shot, and more than 705,000 who got both the flu and COVID vaccines during a single visit. The analysis spanned three years—September 2022 through August 2025—a period when three different versions of the COVID vaccine were in circulation. The team tracked 46 different adverse reactions in the 90 days following vaccination, looking for patterns that might suggest a safety problem when the shots were given together.
The conditions they monitored included cardiovascular events, blood clots, neurological disorders, and immune-mediated complications—the kinds of rare but serious side effects that regulators and clinicians worry about most. When the numbers were tallied, none of these outcomes showed a statistically significant increase in risk among people who received both vaccines simultaneously compared to those who got the flu shot alone. The finding held across all three COVID vaccine iterations studied during the period.
The researchers, all based at the VA St. Louis Health Care System's Clinical Epidemiology Center, emphasized that their results have immediate practical implications. "The findings support the short-term safety of coadministration in older adults and may help inform ongoing vaccine policy discussions and individual risk–benefit assessments," they wrote. For patients and doctors trying to decide whether to schedule two shots on the same day or space them out, this data provides reassurance that convenience need not come at the cost of safety.
The timing of this research matters. Although COVID-19 death rates have declined significantly since the pandemic's peak, the virus continues to cause substantial illness and death in the United States. Between October 2023 and September 2024 alone, the country recorded an estimated 879,000 hospitalizations and 101,000 deaths from COVID-19. Flu remains a persistent threat as well. The ability to protect against both viruses in a single medical visit could simplify vaccination campaigns, reduce barriers to immunization, and ultimately save lives—particularly among older adults and other vulnerable populations who benefit most from both vaccines.
This study represents the kind of real-world evidence that public health officials and vaccine manufacturers have long sought. Rather than relying on small clinical trials conducted before vaccines reached the general population, researchers here examined what actually happened when millions of people received both shots. The VA's integrated health system, with its detailed electronic records and stable patient population, provided an ideal setting for this kind of analysis. The results should help shape how health systems approach vaccination scheduling and how individual patients and their doctors think about the trade-offs between convenience and caution.
Notable Quotes
The findings support the short-term safety of coadministration in older adults and may help inform ongoing vaccine policy discussions and individual risk–benefit assessments.— Study authors, VA St. Louis Health Care System's Clinical Epidemiology Center
The Hearth Conversation Another angle on the story
Why does it matter whether these two vaccines can be given on the same day? Isn't that just a scheduling question?
It seems like scheduling, but it's actually about trust and access. If people worry that combining shots is risky, they might skip one or delay it. This study shows that fear isn't grounded in evidence—both shots together are as safe as one alone.
But weren't these vaccines already tested before they were approved? Why do we need a study of 2.5 million people now?
Clinical trials are small and controlled. They happen in ideal conditions with selected populations. Real-world data tells you what happens when millions of different people—older, sicker, on other medications—actually get the shots. That's where you find rare side effects or unexpected patterns.
The study looked at 46 different adverse reactions. That's a lot to track. Did they find anything concerning at all?
Nothing statistically significant. No increased risk in any of the 46 outcomes they monitored. That's actually the strongest possible result—it's not just "no major problems," it's "we looked hard for problems and found nothing."
The study mentions COVID is still causing substantial illness. Does that change how people should think about getting vaccinated?
It reframes the whole conversation. Yes, COVID is less deadly than it was. But 101,000 deaths in a single year is still enormous. If people can get protected against both flu and COVID in one visit, and it's safe, then the barrier to vaccination drops. More people might actually do it.
Who benefits most from this finding?
Older adults, mainly. They're the ones most vulnerable to both viruses and most likely to benefit from both vaccines. But also anyone managing a chronic illness or with a busy life—anyone for whom one fewer doctor's visit is genuinely meaningful.