Oculo-respiratory syndrome

Overview

Oculo-respiratory syndrome (ORS) is a rare, transient, and self-limiting condition that occurs following influenza vaccination, particularly with the inactivated influenza vaccine. First recognized in Canada during the 2000–2001 flu season, ORS is characterized by the sudden onset of eye and respiratory symptoms within 2 to 24 hours after vaccination. While it can be distressing to patients, ORS is typically benign and resolves without any long-term complications. Its exact cause remains unclear, and it is important to distinguish ORS from an allergic reaction or other adverse vaccine responses.

Causes

The exact mechanism of oculo-respiratory syndrome is not fully understood, but it is believed to involve a non-IgE mediated immune response to components of the influenza vaccine. Possible contributing factors include:

• Immune response to vaccine antigens: Some individuals may develop transient inflammation due to immune activation against viral proteins or other components.

• Contaminants or residuals: The presence of trace amounts of egg proteins, preservatives, or detergents used in vaccine preparation may trigger symptoms in sensitive individuals.

• Prior influenza vaccination: People who have received previous flu vaccines may be more prone to developing ORS in subsequent years, suggesting a primed immune response.

ORS is not considered an allergic reaction and is not associated with anaphylaxis. Most cases have been reported with the inactivated trivalent influenza vaccine and are rare with newer formulations.

Symptoms

Symptoms of oculo-respiratory syndrome typically appear within 2 to 24 hours after receiving an influenza vaccine and last for less than 48 hours. The most commonly reported symptoms include:

• Red eyes (conjunctivitis)

• Sore throat

• Cough

• Runny nose (rhinorrhea)

• Nasal congestion

• Wheezing or shortness of breath

• Facial swelling (rarely)

• Itchy or watery eyes

• Mild fever or malaise

Symptoms are usually mild to moderate in intensity and resolve spontaneously within a couple of days without any specific treatment.

Diagnosis

Oculo-respiratory syndrome is diagnosed clinically based on symptom onset and timing in relation to influenza vaccination. There are no specific diagnostic tests for ORS. Diagnostic steps include:

• Detailed history: Timing of symptom onset (within 24 hours of vaccination) is crucial for diagnosis.

• Physical examination: To rule out more serious allergic or infectious conditions such as influenza, COVID-19, or allergic conjunctivitis.

• Exclusion of anaphylaxis: Lack of systemic allergic features such as hypotension, urticaria, or angioedema helps differentiate ORS from a true allergic reaction.

Laboratory tests and imaging are usually not necessary unless symptoms persist beyond 48 hours or are atypical in presentation.

Treatment

ORS is a self-limiting condition and generally does not require aggressive treatment. Supportive care is the mainstay of management:

• Antihistamines: May help relieve itching or nasal symptoms if present.

• Decongestants: For nasal congestion or runny nose, if needed.

• Lubricating eye drops: For eye irritation or redness.

• Rest and hydration: General supportive measures to aid recovery.

In most cases, symptoms resolve on their own within 24 to 48 hours without any intervention. Hospitalization or emergency treatment is rarely needed unless symptoms are misinterpreted as a more serious condition.

Prognosis

The prognosis for oculo-respiratory syndrome is excellent. It is a benign and temporary condition with full recovery expected within a couple of days. Importantly, ORS does not increase the risk of future serious vaccine reactions, and affected individuals can usually be safely revaccinated in subsequent years under medical supervision.

Public health authorities, including the World Health Organization and health agencies in Canada and the United States, consider ORS a minor and acceptable risk associated with influenza vaccination. Continued vaccination is encouraged due to the much higher risks associated with influenza infection itself.