To the Editors:
The COVID-19 pandemic has led to collapse of national health systems across the globe, overwhelmed by the imbalance between health care needs and availability of human and material resources. To control and prevent further transmission, Cuba has developed intersectoral strategies in which the biotech industry has been deeply involved.[1,2]

One of several products destined for COVID-19 control is Nasalferon, a nasally administered recombinant alpha 2b interferon that acts against viral replication.[3,4] Its use is recommended as a complement to public health measures to reinforce the first line of defense against the virus in the oropharyngeal tract.

From January 14 to 24, 2021, 103 international adult travelers arriving in Cárdenas, Matanzas Province, as well as their 317 close adult contacts—all with initial PCR tests negative for SARS-CoV-2—received Nasaferon.[3] Each was visited daily for 15 days, to determine SARS-CoV-2 infection and observe any adverse events potentially related to the medication. At 15 days, PCR results and clinical examination indicated that no travelers or
contacts had become infected.

Headache (73/420; 17.4%) and weakness (13/420; 3.1%) were the only adverse events notifi ed. All events were mild, transient and limited. No one had to stop using the medication (applied twice daily) because of potentially drug-related adverse events.

Based on our experience, we strongly recommend the use of Nasalferon as an additional tool to prevent SARS-CoV-2 infection in travelers and their close contacts.

This study was part of a larger intervention in Matanzas Province during January and February 2021. Along with the Cárdenas travelers and contacts, workers from three hotels in Varadero Beach—Sol Palmeras, Meliá International and Royalton Hicacos—and from the Las Morlas campsite were also included.