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A Sero-Prevalence Study of Hepatitis A Immunity

Georgina Normandin
Staff Nurse, Communicable Diseases
Calgary Health Region

Background

Infectious hepatitis or Hepatitis A Virus (HAV) is the most commonly reported, immunization-preventable infection that travelers encounter. But not everyone needs to be vaccinated; those previously exposed already have immunity to the virus.

Public health nurses counsel clients coming to the travel clinic about the potential risks of contracting Hepatitis A. They also assess the risk to the traveler of acquiring an infection, based on the type of travel and an individual’s history. Considerations include:

• Short term travel of a month or less is considered a lower risk. 
• Travel itinerary with rural travel and trekking is considered higher risk than urban travel. 
• Frequent traveling to various destinations and leaving on short notice. 
• History of hepatitis A infection or being raised in a country where there is a high incidence of hepatitis A.

Individuals at higher risk of contracting HAV are being encouraged to have blood work to confirm a past infection, saving those with immunity the concern of being infected, and the cost of being needlessly vaccinated. The vaccine costs clients $50.00 a dose, with two doses being required for long term protection.

Research Question

Georgina Normandin a SEARCH II participant and public health nurse with the Calgary Health Region conducted a research project to determine the percentage of clients coming to the region’s Downtown Travel Clinic with HAV immunity, and to identify patterns of HAV immunity in those likely to have been previously exposed to the virus.

Methods

Serology results from 1000 blood samples taken from clients coming to the Calgary Health Region Downtown Travel Clinic showed an overall prior exposure and immunity of 75.8 per cent to HAV. Patterns revealed in the testing include the presence of the HAV antibody increases with age and varies from geographic region to geographic region. A described history of hepatitis; however, is not a good predictor of past infection and immunity to HAV. Many clients who had no history of this illness were positive for antibodies, while others who recalled a hepatitis-like illness thought to be HAV tested negative for antibodies.

Results

Selective screening for HAV immunity is warranted; although, it continues to be important to give detailed advice on universal food and water safety. Factors to be considered for each and every client are:  

• An individual's personal history of having a high likelihood of retaining immunity from an earlier infection, based on knowing their country of origin 
• Past travel experience of the client  
• The client’s planned itinerary and his/her depth of understanding of food and water precautions

These results are now being used at the travel clinic to guide discussions on the use of Hepatitis A vaccine for individuals born and raised in Third World countries, where the incidence of Hepatitis A is higher. In many cases, a simple blood test means the individual does not require Hepatitis A vaccine.

Results of the literature review are now being presented more broadly, for application beyond the clinic and region.