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We are delighted to share some key insights from our recent interview with Dr. Anna Puigdellívol-Sánchez, Editorial Board Member of COVID (ISSN: 2673-8112). She introduced her main research directions and findings, shared her perspective on future research trends in the field, and provided recommendations for preparing for future pandemics.

The following is an interview with Dr. Anna Puigdellívol-Sánchez:

Research Background and Motivation

1. Could you briefly introduce your research background and what inspired you to focus on COVID-19 and long COVID?

My previous research at the University of Barcelona was focused on neuroanatomy and on developing specific models for assessing peripheral nerve regeneration. The experience with 3D reconstructions was applied to assess bias in microscopic cell counting and neuraxial anesthesia, where we proposed a mathematical approach to improve the precision of punctures. I also work as a Family Physician at the Consorci Sanitari de Terrassa (an integral healthcare organization), where I have also studied diverse primary care aspects such as sick leave, dependency, and glucometer accuracy, among others.

The experience with mathematical approaches across all those fields motivated me to analyze the mathematical aspects of the COVID-19 spread and of drugs that could ameliorate it. The current moment, with serious post-pandemic consequences, has led me to study long COVID.

2. What are the key challenges you have encountered in studying COVID-19, and how have you addressed them?

A special challenge is the disparity between data sources in hospital and primary care, which makes it difficult to integrate data from different institutions to conduct multicenter studies. The Consorci Sanitari de Terrassa, as an integral healthcare organization covering a population of about 200,000 inhabitants, is big enough to identify main trends yet small enough to handle the amount of data.

However, we would need multicenter studies to achieve the necessary statistical significance for concrete subgroups in prospective studies.

COVID-19 Treatment Studies

3. Your research explores treatment methods for COVID-19. Could you highlight the key research results you have identified?

The main finding is that patients receiving a chronic prescription of antihistamines presented about half the hospital admissions (or a 40% reduction if being treated with more than 8 chronic treatments), which is consistent with the published experience in the nursing home in Yepes, where all residents were infected in the first wave, but none died or required hospital admission after being treated with antihistamines and azithromycin.

4. How do these treatments compare in terms of efficacy, safety, and accessibility? Are there any specific patient populations that benefit more from certain treatments?

No other available treatment has shown a greater than 50% reduction in hospital admissions. The more expensive antihistamine treatment (bilastine) has a cost below 10 euros in Spain, while the one used in Yepes in their pragmatic experience (cetirizine) has a cost below 5 euros. We have observed this reduction in our institution, where about 100 physicians freely prescribe the antihistamine drug they prefer, and we still observe the reduction in hospital admissions. Furthermore, many antihistamines can be bought at the pharmacy without a medical prescription, and thus, they may be used to treat the common cold (even if it is a COVID infection with a false negative test).

Long COVID Epidemiology Studies

5. Could you explain the current understanding of long COVID based on your studies?

For the moment, we see patients with severe pain and memory complaints, among other nonspecific conditions, where specific blood tests are normal. Some images that could be related to microangiopathy are seen in 3T MRI, but they are difficult to differentiate from those commonly associated with age, and we do not have easy access to 3T MRI. Currently, we do not have a good understanding of this phenomenon.

6. How does long COVID impact different demographics, and what are the long-term implications for public health?

The good news is that long COVID may be “persistent” but not always disabling, as shown by the finding that more than 90% of patients who required sick leave were back at work after one year (77% of them within the first month). We are now concerned about the increase in thrombotic events. We do not have a clear explanation for this, and the short-term consequences are uncertain. Another concern is the exponential increase in long COVID after the third documented infection. Epidemiological data show that COVID may be detected this week (the first in September 2025) in random samples of 24% of symptomatic children in the northeast of Spain. They will most likely spread it to surrounding adults, who will probably present only a mild cough. Since in most cases it will not be diagnosed, future nonspecific health complaints will not be categorized as long COVID.

International Collaboration

7. In your previous research, you have worked with scholars from other countries. Could you share your thoughts on how these international collaborations have influenced your approach to studying COVID-19?

When trying to address unsolved aspects of medicine (nerve regeneration, improvement of anesthetic punctures, cell quantification), one realizes how true a phrase I read many years ago is: “When you are a bachelor student, you believe you know everything; when you realize you know nothing, you get the degree; and when you really realize that neither you nor others know anything, then you get the PhD.”. Throughout previous scientific collaborations, you realize that you can only improve a very minor and specific aspect of a particular field, one that is probably interesting to a few colleagues who live far away. And when the COVID-19 pandemic began, I thought, “well, nobody knows anything about this”, as usual, but I am used to it. Since previous experience with mathematical approaches had been productive in both neuroanatomy, anesthesiology, and research on sick leave and dependency, I thought I could face COVID-19 and find another small, concrete detail that could be helpful to somebody.

Future Directions and Recommendations

8. Based on your findings, what are the critical areas for future research on COVID-19 treatments and long COVID?

• A prospective and multicenter study of antihistamines combined with azithromycin is needed to confirm the benefits that have been described in pragmatic medical practice;
• A prospective comparison between vaccine techniques is also needed: RNA vaccines, protein recombinant–based vaccines, and inactivated virus vaccines should be compared in a trial, and the different vaccines should be available for individual choice;
• Trials including patients with mild long COVID, including children and young people, should be conducted with 3T MRI to rule out early microangiopathy;
• Furthermore, several techniques of brain stimulation could be tested in patients with more severe memory complaints;
• Finally, if an increase in thrombotic phenomena is detected in other areas, anti-nucleocapsid antibodies could help to identify undiagnosed infections (although more information about the sensitivity of these antibodies is required).

9. Do you have any recommendations or insights on the prevention and response to the next pandemic?

For the moment, I am worried about the current response to COVID-19: the lack of strong recommendations for preventive masks for symptomatic patients and for the healthcare workers attending them, even in well-ventilated facilities. The data on hospitalizations in different countries is no longer updated on “Our World in Data”. The early detection of variants in wastewater is not effectively linked to forecasting upcoming hospitalization peaks. Furthermore, the USA does not share its data with the WHO. Altogether, we are losing the sources of information we once had, before this threat even ended.

Thank you for your interest in covering all those aspects.

References

1. COVID-19 in Relation to Chronic Antihistamine Prescription (2024, Microorganisms) https://www.mdpi.com/2076-2607/12/12/2589.
2. Antihistamines and azithromycin as a treatment for COVID-19 on primary health care - A retrospective observational study in elderly patients (2021 Pulm Pharmacol Ther) https://pubmed.ncbi.nlm.nih.gov/33465426/.
3. Antihistamines as an early treatment for Covid-19 (2023, Heliyon) https://pubmed.ncbi.nlm.nih.gov/37128299/.
4. Long COVID Syndrome Prevalence in 2025 in an Integral Healthcare Consortium in the Metropolitan Area of Barcelona: Persistent and Transient Symptoms (2025, Vaccines) https://www.mdpi.com/2076-393X/13/9/905.

Dr. Anna Puigdellívol-Sánchez’s Special Issue in COVID:

“COVID and Public Health”