When it comes to breakthrough cases, are we ignoring long Covid once again?

On 1 May, the US Centers for Disease Control and Prevention stopped tracking breakthrough infections that did not lead to hospitalization or death. Its rationale was to “​​maximize the quality of the data collected on cases of greatest clinical and public health importance”, making the continued assumption that non-hospitalized Covid cases are not important but “mild”: without complications, manageable at home, where patients fully recover in two weeks.

I have dealt with persistent symptoms for 17 months – an illness now called “long Covid” – and not collecting data based on this assumption is an enormous mistake, one that has persisted throughout the pandemic and has severe consequences moving forward.

We know much more about long Covid than we did this time last year – enough for us to know it’s severe. Research has found ongoing endothelial dysfunction, hypometabolism in the brains of long Covid patients, microclots in long Covid blood samples, reduced aerobic capacity and impaired systemic oxygen extraction in non-hospitalized patients without cardiopulmonary disease, disrupted gut microbiota that persists over time, damage to corneal nerves, immunologic dysfunction persisting for at least eight months, numerous findings of dysautonomia (a common post-viral disorder of the autonomic nervous system), and countless other conditions.

In a cohort of non-hospitalized patients, 31% were dependent on others for care; our own paper from the Patient-Led Research Collaborative found over 200 multi-systemic symptoms that impaired the ability to work and function in daily life. We also found high levels of cognitive dysfunction and memory loss that were as common in 18-29 year olds as those over 70, a finding that is starting to be highlighted in children and teenagers as well.

The mechanisms for the pathophysiology behind long Covid are complex; one comprehensive paper suggested “consequences from acute Sars-CoV-2 injury to one or multiple organs, persistent reservoirs of Sars-CoV-2 in certain tissues, re-activation of neurotrophic pathogens such as herpesviruses under conditions of Covid-19 immune dysregulation, Sars-CoV-2 interactions with host microbiome/virome communities, clotting/coagulation issues, dysfunctional brainstem/vagus nerve signaling, ongoing activity of primed immune cells, and autoimmunity due to molecular mimicry between pathogen and host proteins” as a few of the many possibilities. This type of complex research will take years to undertake and uncover, leaving patients suffering without treatment.

And all of this does not include the eventual “long” long-term findings that may be revealed in the decades to come. Recent studies show cognitive decline even in truly mild recovered patients; some doctors are worried about the possibility of a future wave of dementia or Alzheimer’s patients, a theme echoed at a recent NIH conference on neuropsychiatric effects of Covid.

Related: Brain fog, phantom smells and tinnitus: my 4 months (and counting) of Covid-19 | Hannah Davis

Long Covid is generally left out of policy conversations, instead getting lumped in with mild cases. The WHO and CDC consider mild patients to be those with Covid symptoms without pneumonia or low oxygen levels, and the NIH similarly defines them as individuals with Covid symptoms without shortness of breath, difficulty breathing, or abnormal chest imaging. By these definitions, patients with cognitive dysfunction, microclots, months-long fevers, tremors, dysautonomia, and those who are no longer able to participate in daily life – including not being able to walk, work, drive, go to school, or take care of their kids – are all considered “mild”.

In unvaccinated people, current estimates from the Office of National Statistics in the UK are that 11-18% of patients will get long Covid, measured by having symptoms at 12 weeks. What we don’t know – but need to know to make any meaningful policy decisions around vaccinated people and the pandemic moving forward – is how common breakthrough cases are, how common long Covid is in these breakthrough cases, and how breakthrough long Covid compares with long Covid in unvaccinated infected individuals, in terms of severity, duration, and pathophysiology.

Related: ‘What is happening to me?’ The teenagers trying to make sense of long Covid

Right now, the available data that we do have is less than ideal. A small study out of Israel showed 19% of breakthrough cases had persisting symptoms at six weeks, on par with the rate of long Covid in unvaccinated infections. Early studies showed that breakthrough infections were rare, but most of them were done prior to Delta; new studies from Mayo Clinic and Israel suggest lower vaccine effectiveness with this new variant, meaning more breakthrough infections may happen.

We don’t have to make conclusions based on these limited data, and I would argue that we actually shouldn’t. What we do need to do is collect more data – to track cases until we can adequately and comprehensively calculate the risk not only of hospitalization and death, but of long Covid, and incorporate that morbidity into our public policy equations. Without data, decisions will be made that will continue to kill and disable people. Without taking long Covid into consideration, any resulting policy is not complete, and any resulting risk assessment is not accurate.

• Hannah Davis is an independent researcher and artist based in Brooklyn. She is an advocate for patient-led research