U.S. veterans' study reveals key insights into Long COVID and protective role of vaccination

By Hugo Francisco de SouzaDec 12 2023Reviewed by Susha Cheriyedath, M.Sc.

In a recent study published in the journal JAMA Network Open, researchers evaluated the clinical characteristics and patterns of post-COVID-19 condition (PCC) among United States veterans. Their study cohort included 388,980 veterans who were documented to experience shortness of breath, fatigue, cough, brain fog, and alterations to their olfactory and auditory sensitivity. Encouragingly, vaccination was found to have a protective effect on these individuals. This study highlights the need for intensive, routine, and accurate documentation of symptoms in COVID-19 survivors for both research and clinical care.

Study: Rates of ICD-10 Code U09.9 Documentation and Clinical Characteristics of VA Patients With Post–COVID-19 Condition. Image Credit: Lightspring / Shutterstock

What is PCC?

The coronavirus disease 2019 (COVID-19) has been estimated to have claimed more than 7 million lives and infected more than 772 million people since the beginning of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak in late 2019. In addition to the unprecedented socioeconomic, health, and infrastructure impacts of the pandemic, a growing body of evidence has identified a novel condition that plagues survivors of the disease.

Colloquially called ‘Long COVID,’ the clinically termed post-COVID-19 condition (PCC) or post-acute-COVID-19 syndrome (PCAS) refers to the persistence and, in some cases, development of novel COVID-19 symptoms long after the initial infection has passed. Both the World Health Organization (WHO) and the United States (US) Centers for Disease Control and Prevention (CDC) have defined the condition as the persistence of COVID-19 symptoms for a minimum of 4 weeks following discharge from routine COVID-19 care.

Alarmingly, these symptoms have been found to persist for months or even years following recovery from COVID-19, resulting in severe reductions to patients’ quality of life and socioeconomic loss on a global scale. Despite being novel and poorly understood, recent research has estimated that between 10-30% of COVID-19 survivors experience PCC, with numeric estimates of over 65 million afflicted individuals.

“An International Statistical Classification of Diseases, Tenth Revision (ICD-10) code for PCC became available in the US on October 1, 2021, which affords the possibility of investigating the correlates of documentation of PCC care by clinicians.”

Unfortunately, more than two years later, information on patients seeking medical treatment for PCC and clinicians’ documentation of care remains lacking. Understanding the patient and demographic characteristics involved in PCC care may give insight into the mechanisms underpinning the condition and the existence of multiple phenotypes of PCC, and most importantly, it may help evolve government policy to provide better adequate care where it is required most.

About the study

In the present study, researchers aimed to evaluate the prevalence rates, clinical settings, risk factors, and common symptoms of Long COVID in US Army veterans (VA) with documented ICD-10 code U09.9. The study identified all VAs with positive VA electronic health records (EHR) between October 1, 2021, and January 31, 2023.

Of the 411,837 identified individuals, Vas who did not visit the US Veterans Affairs center in the 18 months preceding positive COVID-19 antigen/RT0PCR tests were excluded (n = 22,857), leaving a final analytic cohort of 388,980 patients (87.3% male). Study methodology and reporting complied with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guidelines.

Data collection included sociodemographic (age, sex, ethnicity/race), geographic (pin code of the current residence), and clinical characteristics (medical prescriptions and records of symptoms and comorbidities) for the two years preceding initial COVID-19 infection. Additionally, vaccination status (and, if relevant, the type of vaccine used) was recorded.

Of the more than 200 symptoms listed by the WHO and CDC, researchers identified 15 prespecified symptoms most common in US PCC patients via the use of the VINCI-CSDR natural language processing algorithm. To understand the development of novel symptoms, 650 patients were chosen and randomized for monthly follow-up (for six months) following study enrolment.

Statistical analyses included calculating Cox proportional hazard regression coefficients (hazard ratios [HRs]), corrected for age, sex, and ethnicity/race.

Study findings

The present study revealed that the positive incidence of code U09.9 was 4.79% (at six months) and 5.28% (at twelve months following initial COVID-19 diagnosis). The highest-risk individuals included older-aged VAs, females, and Hispanic/Latino race/ethnicity. Infection and PCC severity were found to be the most crucial variables in VAs seeking medical assistance for PCC.

Encouragingly, vaccination (both primary and, to a greater extent, primary + booster) reduced the severity of PCC substantially despite leaving duration highly variable. Surprisingly, documentation and medical PCC care varied considerably due to geographic location.

“The most common symptoms recorded in the medical record in patients with documented U09.9 code were shortness of breath, fatigue, cough, reduced cognitive function and change in smell and/or taste.”

Of the patients chosen for monthly follow-up, 64.9% developed novel COVID-19 symptoms during the six months following study enrolment, highlighting that the PCC phenotype is both more variable and faster-evolving than previously thought.

“Future studies should examine the long-term trajectory of individuals with U09.9 documentation.”