I’m supportive of vaccines and understand their importance, particularly for healthcare workers. My question is about those of us who developed significant, persistent post-viral-type symptoms following COVID vaccination and who now experience similar problems with other vaccines, including the flu vaccine.
If mandatory vaccination for healthcare workers is going to be reconsidered, how can we plan for people in this situation? What research is being done to understand why some individuals appear to have prolonged immune or inflammatory reactions, how to identify who may be at greater risk, and—most importantly—how to make future vaccination safer for us?
I want to be able to receive the protection vaccines provide. What I would like to understand is what medicine is doing to help people who have experienced these reactions safely get there.
Jody, this is an excellent question, and I think medicine needs to be able to hold two thoughts at the same time.
Vaccines prevent enormous amounts of illness, hospitalization, and death. And some people report significant, persistent symptoms beginning after vaccination. Those people should neither be ignored nor automatically told that because an adverse event is uncommon, it could not have happened to them.
The difficult part is determining causation. When symptoms begin after vaccination, the timing is important, but timing alone cannot establish that the vaccine caused them. This becomes especially complicated with syndromes involving fatigue, dysautonomia, neuropathic symptoms, brain fog, exercise intolerance, and other symptoms that also occur after viral infections, including COVID itself.
There is, however, real research being done.
The Yale LISTEN group, including Akiko Iwasaki and Harlan Krumholz, has been studying people who report what they call post-vaccination syndrome. In one study, they found differences in several immune-cell populations compared with controls, evidence of recent EBV reactivation in some participants, and persistent circulating spike protein in a subset. Those findings are interesting, but the study was small—42 affected individuals and 22 controls—and does **not** yet establish either a diagnostic biomarker or a mechanism. It tells us where to look next, not that we have solved the problem.
A larger descriptive study from the same program has documented the symptoms and experiences of 241 people reporting persistent illness after COVID vaccination. Again, that establishes that there is a population worth studying; it does not by itself prove that every symptom was vaccine-caused.
Researchers are also examining whether some of the biology overlaps with long COVID—things such as dysautonomia, abnormal immune activation, autoimmunity, neuropathy, and viral reactivation. Interestingly, long-COVID research itself is increasingly finding that different patients may have different biological mechanisms rather than one single disorder. A 2026 NIH-reported study, for example, found evidence that antibodies targeting parts of the nervous system may contribute to neurological symptoms in a subset of long-COVID patients.
What we **do not have yet** is probably the most important part of your question: we do not currently have a validated blood test that tells us, “You are the person likely to develop prolonged symptoms after this vaccine.” Nor do we have a proven pretreatment regimen that reliably prevents such a reaction.
And I would be very cautious of anyone selling supplements, anticoagulants, “spike detox,” plasmapheresis, or other treatments based on preliminary mechanistic theories. A hypothesis is not yet a therapy.
Where I think healthcare vaccination policy needs some nuance is here: a mandate should never substitute for clinical judgment. CDC already distinguishes between contraindications and precautions and recommends individualized assessment in situations involving significant prior reactions. For COVID vaccines, for example, previous vaccine-associated myocarditis or pericarditis is specifically a precaution for which subsequent vaccination generally should be avoided, and people with certain allergic reactions may be evaluated for another vaccine platform. Complex cases can also be referred through CDC's Clinical Immunization Safety Assessment (CISA) program.
For someone with the history you describe—particularly repeated substantial reactions after different vaccines—I would want an occupational-health physician working with an allergist/immunologist, and depending upon the symptoms perhaps neurology or a dysautonomia specialist, to document exactly what occurred, when it occurred, how long it lasted, and whether an identifiable syndrome can be established. That record should matter when determining whether another vaccination, a different vaccine formulation, postponement, or a medical exemption is appropriate.
Unfortunately, the evidence for predicting recurrence after an influenza vaccine or for choosing the safest future vaccine in someone with this broader pattern is even thinner.
So my answer is partly reassuring and partly unsatisfying: **medicine is investigating this, but we don't yet have the predictive tools or treatments that you are quite reasonably asking for.**
I also think people who have experienced unusual reactions are an especially important reason to do this research carefully. Dismissing them drives people away from vaccination. Studying them may ultimately allow us to identify who is susceptible, understand why, and make vaccination safer for precisely the people who still want its protection.
There are other types of influenza vaccines out there -
I’m supportive of vaccines and understand their importance, particularly for healthcare workers. My question is about those of us who developed significant, persistent post-viral-type symptoms following COVID vaccination and who now experience similar problems with other vaccines, including the flu vaccine.
If mandatory vaccination for healthcare workers is going to be reconsidered, how can we plan for people in this situation? What research is being done to understand why some individuals appear to have prolonged immune or inflammatory reactions, how to identify who may be at greater risk, and—most importantly—how to make future vaccination safer for us?
I want to be able to receive the protection vaccines provide. What I would like to understand is what medicine is doing to help people who have experienced these reactions safely get there.
Jody, this is an excellent question, and I think medicine needs to be able to hold two thoughts at the same time.
Vaccines prevent enormous amounts of illness, hospitalization, and death. And some people report significant, persistent symptoms beginning after vaccination. Those people should neither be ignored nor automatically told that because an adverse event is uncommon, it could not have happened to them.
The difficult part is determining causation. When symptoms begin after vaccination, the timing is important, but timing alone cannot establish that the vaccine caused them. This becomes especially complicated with syndromes involving fatigue, dysautonomia, neuropathic symptoms, brain fog, exercise intolerance, and other symptoms that also occur after viral infections, including COVID itself.
There is, however, real research being done.
The Yale LISTEN group, including Akiko Iwasaki and Harlan Krumholz, has been studying people who report what they call post-vaccination syndrome. In one study, they found differences in several immune-cell populations compared with controls, evidence of recent EBV reactivation in some participants, and persistent circulating spike protein in a subset. Those findings are interesting, but the study was small—42 affected individuals and 22 controls—and does **not** yet establish either a diagnostic biomarker or a mechanism. It tells us where to look next, not that we have solved the problem.
A larger descriptive study from the same program has documented the symptoms and experiences of 241 people reporting persistent illness after COVID vaccination. Again, that establishes that there is a population worth studying; it does not by itself prove that every symptom was vaccine-caused.
Researchers are also examining whether some of the biology overlaps with long COVID—things such as dysautonomia, abnormal immune activation, autoimmunity, neuropathy, and viral reactivation. Interestingly, long-COVID research itself is increasingly finding that different patients may have different biological mechanisms rather than one single disorder. A 2026 NIH-reported study, for example, found evidence that antibodies targeting parts of the nervous system may contribute to neurological symptoms in a subset of long-COVID patients.
What we **do not have yet** is probably the most important part of your question: we do not currently have a validated blood test that tells us, “You are the person likely to develop prolonged symptoms after this vaccine.” Nor do we have a proven pretreatment regimen that reliably prevents such a reaction.
And I would be very cautious of anyone selling supplements, anticoagulants, “spike detox,” plasmapheresis, or other treatments based on preliminary mechanistic theories. A hypothesis is not yet a therapy.
Where I think healthcare vaccination policy needs some nuance is here: a mandate should never substitute for clinical judgment. CDC already distinguishes between contraindications and precautions and recommends individualized assessment in situations involving significant prior reactions. For COVID vaccines, for example, previous vaccine-associated myocarditis or pericarditis is specifically a precaution for which subsequent vaccination generally should be avoided, and people with certain allergic reactions may be evaluated for another vaccine platform. Complex cases can also be referred through CDC's Clinical Immunization Safety Assessment (CISA) program.
For someone with the history you describe—particularly repeated substantial reactions after different vaccines—I would want an occupational-health physician working with an allergist/immunologist, and depending upon the symptoms perhaps neurology or a dysautonomia specialist, to document exactly what occurred, when it occurred, how long it lasted, and whether an identifiable syndrome can be established. That record should matter when determining whether another vaccination, a different vaccine formulation, postponement, or a medical exemption is appropriate.
Unfortunately, the evidence for predicting recurrence after an influenza vaccine or for choosing the safest future vaccine in someone with this broader pattern is even thinner.
So my answer is partly reassuring and partly unsatisfying: **medicine is investigating this, but we don't yet have the predictive tools or treatments that you are quite reasonably asking for.**
I also think people who have experienced unusual reactions are an especially important reason to do this research carefully. Dismissing them drives people away from vaccination. Studying them may ultimately allow us to identify who is susceptible, understand why, and make vaccination safer for precisely the people who still want its protection.
There are other types of influenza vaccines out there -