VALUE OF ZANAMIVIR PROPHYLAXIS IN A NURSING HOME OUTBREAK OF INFLUENZA A

W. LEE*, A. MCGEER, M. MCARTHUR, P. FRIEDMAN, A. KAM, T. MAZZULLI, M. LOEB, A. E. SIMOR Mount Sinai Hospital, Lincoln Place Nursing Home, Sunnybrook and Women's College Health Sciences Centre and the University of Toronto, Toronto, Ontario.

Objective: To assess the impact of zanamivir prophylaxis in controlling influenza A outbreaks in long term care.

Design: Investigation of an influenza A outbreak in a 256 bed nursing home.

Methods: Outbreak-associated illness was defined as acute respiratory illness associated either fever or malaise and with a positive culture or antigen test for influenza A. Resident symptoms were assessed daily. Nasopharyngeal swabs were performed on all residents with any respiratory symptom.

Intervention: Standard precautions for outbreak control, including vaccination, isolation of ill residents, exclusion of ill staff, restriction of visitors and cancellation of shared activities. Staff classified residents as capable of using a diskhaler or not, residents deemed capable were offered zanamivir. Residents not capable, and those refusing zanamivir were offered amantadine.

Results: Zanamivir was not given to 52/249 (21%) residents: 42 were judged unable to use the inhaler, 3 preferred AM, 2 refused all therapy, and 5 were out of the facility. An additional 41 (16.5%) residents were switched to amantadine after difficulty with two attempts at inhalations. A total of 39 cases were identified. After the start of antiviral prophylaxis, 4/82 (4.8%) residents prescribed amantadine, 7/146 (4.8%) prescribed zanamivir, and 1 of 2 refusing any prophylaxis developed illness meeting the case definition (P=.01). No side effects were identified due to zanamivir, and no resident required discontinuation of amantadine due to side effects.

Conclusions: Zanamivir was as effective as amantadine in the prevention of influenza A. Use of zanamivir was associated with termination of the outbreak. The majority (157/239, 66%) of residents in this nursing home were able to comply with inhalations of zanamivir.

 

Presented at:

COMMUNITY AND HOSPITAL INFECTION CONTROL ASSOCIATION - CANADA (CHICA) Conference, The Sheraton Centre, Toronto ON, Canada, May 29-31, 2000.