PAIS IMPACT | The Amsterdam UMC Post-COVID Expertise Center: Bridging Research and Recovery

At the Amsterdam institute for Immunology and Infectious diseases (AI&I), we focus our research and outreach on three key themes: Post-Acute Infection Syndrome (PAIS), Immunomonitoring, and Vaccination. Each quarter, we highlight one of these areas through a dedicated series of articles. This quarter (Q3 2025), our spotlight is on PAIS. In this article, we focus on the impact of PAIS research, with special attention to the work of the Amsterdam UMC Post-COVID Expertise Center.

The long-term effects of COVID-19 continue to challenge patients and healthcare systems worldwide. At Amsterdam UMC and partner centers across the Netherlands, a unique, collaborative approach is making a real difference for those living with post-COVID syndrome. By combining research, national data sharing, and patient-centered care, these expert teams are not only uncovering the causes of persistent symptoms, but also developing practical solutions that improve lives today, while paving the way for better treatment and understanding in the future.

Patient journey

Consultations for adults at the post-COVID expertise center are sometimes held in the dark, says internist-infectiologist Roosmarijn van Hooijdonk. In the waiting room, there is a lounge chair for patients to rest between tests. All patients have severe, lingering symptoms after a SARS-CoV-2 infection, limiting their daily functioning. They are referred by their GP and selected for treatment at Amsterdam UMC. Complaints vary widely, over 200 symptoms are associated with post-COVID, and likely multiple underlying causes exist. Common issues include post-exertional malaise (PEM), where even minor physical or mental effort leads to various complaints like fatigue or pain, and Postural orthostatic tachycardia syndrome (POTS), a syndrome causing rapid heartbeat and dizziness upon standing. Cognitive problems, such as poor concentration and sensitivity to light and sound, are also frequent, as are menstrual disturbances in women.

Patients complete questionnaires before a comprehensive one-time consult, including medical history, physical exams, grip strength tests, and the NASA lean test for POTS, where the patient lies down for 5 to 10 minutes, then stands up, and changes in heart rate and blood pressure are measured. Children also receive heart tests, lung tests and neurological tests. Lab work follows, and initial findings are discussed with the patient. Due to low stamina, follow-up appointments are usually virtual. Cases are reviewed in multidisciplinary meetings, both locally and nationally, to share insights and discuss new treatments. Local meetings include internists, pharmacists, and psychologists, with rheumatologists often consulted. Nationally, cases and new treatment insights are shared among direct care providers from the post-COVID expertise centers. These meetings ensure consistent care, facilitate research coordination, and allow for the exchange of practical advice, such as treatment options or referrals, to optimize patient care and research.

Collaborative research

The approach is standardized across all Dutch post-COVID centers (Amsterdam UMC, Erasmuc MC, Maastricht UMC+, UMC Utrecht, Leiden UMC, UMC Groningen) to enable scientific analysis across the country. Amsterdam UMC has seen about 250 adult patients; nationwide, nearly 15,000 have registered. The centers aim to develop knowledge to benefit all patients, focusing on data collection about symptoms, disease progression, and treatment response.

‘There are many ways to make an impact. For some patients, it means finally meeting someone who understands their whole story and truly knows what they’re going through. Many have had to explain symptoms like PEM themselves, bringing information to their doctors rather than receiving it. It’s a relief for them to finally feel understood and connected. As a physician, you hope to find answers, knowing that PAIS could affect anyone.’

Roosmarijn van Hooijdonk

Internist-infectiologist

Innovative treatment

Treatment targets manageable symptoms first, such as POTS, which often improves with compression stockings and increased salt intake. Occupational therapy helps patients manage PEM by teaching energy conservation strategies. Underlying conditions like thyroid issues or iron deficiency are also addressed. Some patients receive experimental off-label medications, such as low-dose naltrexone, which is also used off-label for ME/CFS, to treat PEM. Children may participate in N-of-1 trials with alternating medication and placebo periods.

As Dr. van Hooijdonk observes, ‘Patients often underestimate the severity of their symptoms. After we prescribe them compression stockings for POTS, they come back and say, ‘Now I can cook a meal standing at the counter, instead of sitting at the table or having to do it in stages.’ They hadn’t realized how much their abilities had changed until they experienced the improvement.’

The centers collaborate closely, sharing data and insights to identify patterns and improve care. Research into post-COVID causes focuses on autoimmunity, persistent IDO-2 enzyme activity, and mitochondrial dysfunction. Multiple clinical trials are underway, including antibody filtration, IDO-2 inhibition, and testing new drugs to improve energy and reduce pain. While the main focus of the post-COVID expertise centers is patient care, a ZonMw evaluation study is linked to their work, enabling a case-control study with controls from another cohort. Dr. van Hooijdonk: ‘It’s crucial to focus on post-COVID now, as we have a unique opportunity with many patients affected by a single infection. This may help us gain valuable knowledge for the entire PAIS group.’

The goal is to have more answers by the end of 2026, but the disease remains complex. The first breakthrough will likely be improved diagnosis.

As Dr. van Hooijdonk explains, ‘An improved diagnosis would make a significant difference for patients, offering recognition and validation on many levels. It would also help doctors, knowing the underlying pathophysiology and having a test would allow us to tailor treatments more effectively. For patients, a clear diagnosis is important not just for themselves and their families, but also for employers and insurance physicians. Many patients have to reapply for disability benefits every two years, having to prove they haven’t improved. Being able to say, ‘This is my diagnosis, I know it for sure,’ would be a huge relief.’

Text: Esmée Vesseur and Roosmarijn van Hooijdonk