Antiviral Recommendations for Residents and Staff during a Confirmed Influenza Outbreak

There are currently two antiviral drugs that are licensed in Canada for the treatment and prophylaxis of influenza A and B, including oseltamivir (Tamiflu) and zanamivir (Ralenza). These medications are neuraminidase inhibitors which work by blocking the exit of the influenza virus from the respiratory cells, therefore preventing further replication of the virus. For this reason, when using antivirals for the treatment of influenza, it is important that they are initiated as soon as possible within 48 hours of symptom onset.

Ottawa Public Health (OPH) recommends oseltamivir as the drug of choice for both treatment and prophylaxis of residents in long-term care homes (LTCHs) for the following reasons:

• The use of Zanamivir has not been proven effective for prophylaxis of influenza in the LTCH setting
• Elderly individuals may have difficulty inhaling zanamivir
• Zanamivir is not recommended for treatment or prophylaxis of Influenza in individuals with underlying respiratory conditions such as chronic obstructive pulmonary disease or asthma due to the risk of bronchospasm
• Reimbursement for zanamivir for residents occurs only when the predominant strain is resistant to oseltamivir

Management of staff

It is important for staff to be advised upon hire about the influenza policy of the facility and/or their collective agreement, and the options available to them in the event of an influenza outbreak if they are not immunized for any reason.

When an influenza outbreak occurs, staff must obtain prescriptions for antiviral medication from their own health care provider and are responsible for their own antiviral-related expenses, unless they have coverage through a company or private health insurance plan. They are not eligible for prescription drug coverage under any circumstances from the Ontario Drug Program (ODP). Only under very specific circumstances, immunized health care workers may be eligible for reimbursement through the High Intensity Needs Fund (HINF).

During a laboratory-confirmed influenza outbreak, when the circulating strain is not well-matched by the vaccine, antiviral prophylaxis should be offered to all staff, regardless of vaccination status, until the outbreak is declared over, based on consultation with OPH.

Immunized Staff

• Staff immunized ≥ 2 weeks prior to outbreak declaration, whether with an inactivated or live attenuated influenza vaccine (LAIV), have no  work restrictions, provided they are feeling well
• Staff immunized ≤ 2 weeks with inactivated influenza vaccine prior to outbreak declaration, should take antiviral prophylaxis until immunity is reached or until the outbreak is declared over, whichever is shorter
• Staff immunized ≤ 2 weeks with LAIV (Flumist) should not receive antiviral treatment or prophylaxis for at least 2 weeks after receipt of LAIV, unless medically indicated, so that the antiviral agents do not kill the replicating virus from the administered vaccine. If antiviral agents are administered within this time frame, revaccination should take place immediately with an inactivated influenza vaccine

Unimmunized Staff

• Unimmunized staff should be offered vaccine and take antiviral prophylaxis until immunity is reached or until the outbreak is declared over, whichever is shorter
• Unimmunized staff who refuse to be immunized must take  antiviral prophylaxis until the outbreak is declared over; staff may work with residents as soon as they start antiviral prophylaxis
• Staff accepting to be immunized, but refusing antiviral medication, should NOT be permitted to work in the outbreak-affected area for a two week period. Prior to being reassigned to another unit, they must be asymptomatic for 72 hours (3 days)
• Flumist is a vaccine option in Ontario that is only publicly funded for children from 2-17 years of age. If a staff member or resident chooses to be immunized with Flumist privately, it is recommended that LAIV (Flumist) not be administered until 48 hours after antiviral treatment or prophylaxis for influenza is stopped

Management of residents

Prophylaxis

• During a laboratory-confirmed influenza outbreak, antiviral prophylaxis should be offered to all residents in the outbreak-affected area who are NOT already ill with influenza, regardless of immunization status, until the outbreak is declared over
• If respiratory symptoms develop in a resident while on prophylaxis, the dose should be switched to a treatment dose for five days. After five days, if influenza is not lab confirmed, the resident should return to the prophylactic dose until the end of the outbreak.

Treatment

Once an outbreak has been laboratory-confirmed as influenza, additional laboratory confirmation of new cases is not required to begin treatment of residents who meet case definition. It is important that:

• Antiviral treatment of ill residents who meet case definition is started as soon as possible, and within 48 hours of symptom onset
• Ill residents remain in their rooms for the duration of the antiviral treatment, which should be a total of five days

Circumstances that may affect decisions regarding use of antiviral medication

• If the resident meets case definition and has been symptomatic for MORE than 48 hours and antiviral treatment has NOT been started, use Appendix A for making decisions about the use of antivirals
• If the outbreak is ongoing when the five-day treatment course ends AND the resident did NOT have lab-confirmed influenza (either the resident was never tested or had a negative influenza lab result), the resident should be switched to a prophylactic dose until the outbreak is declared over. This is recommended in case of a potential outbreak caused by more than one agent (See Appendix B)

When antiviral medications do not control the outbreak

If new cases continue to appear 72 to 96 hours after the start of antivirals, consider the following:

• The new cases could be caused by another organism
• There could be compliance/adherence issues
• Resistance to the antiviral medications may have developed in the circulating strain

In the event that the outbreak is not controlled with antiviral use:

• Consult with the OPH Outbreak Management team to determine if the antiviral agents should be continued

References:

• Hoffman-La Roche Limited, Tamiflu Product Monograph, Jan 2015
• AMMI  Canada  Guidelines,  Update  on  Influenza  Antiviral  Drug  Treatment  and  Prophylaxis for the 2015-2016 Influenza Season, 2016
• AMMI Canada Guidelines, Guidance for Practitioners on the Use of Antiviral Drugs to Control Influenza Outbreaks in Long-Term Care Facilities in Canada, 2014-2015 Season, 2015
• AMMI Canada Guidelines, The Use of Antiviral Drugs for Influenza: A Foundation Document for Practitioners, 2013
• Canadian Immunization Guide, Canadian Immunization Guide Chapter on Influenza and Statement on Seasonal Influenza Vaccine for 2016-2017, 2016
• Ministry of Health and Long-Term Care, A Guide to the Control of Respiratory Infection Outbreaks in Long-Term Care Homes, Nov 2015