Effectiveness of Oseltamivir Prophylaxis in Influenza Outbreaks in Residential Aged Care

Abstract

Influenza outbreaks in Aged Care Facilities (ACFs) can lead to hospitalizations and deaths. Influenza can spread rapidly through ACFs if precautionary measures are not taken. Along with influenza vaccination and precautionary hygiene measures, Oseltamivir Prophylaxis (OP) may be effective in reducing the attack rate of influenza by preventing new cases. A cohort study was carried out to investigate the effectiveness of OP use during influenza outbreaks in ACFs located within South Western Sydney Local Health District from 1 January 2015 to 31 December 2018. The main outcome assessed was the rate of OP failure (new cases of influenza in patients treated with OP) among ACF residents. Subgroups and various predictors of OP failure were investigated including presence of a dementia ward, high care ward, and days to Public Health Unit (PHU) notification. The cohort consisted of 86 ACF outbreaks involving 10,064 residents. OP prevented 90% of influenza cases during influenza outbreaks [0.1 RR (95% confidence interval (CI): 0.08–0.12); P < 0.0001]. ACFs with dementia wards had a 44% (0.56 relative risk (RR) (95% CI: 0.34–0.93); P < 0.05) lower OP failure rate. ACFs with high level care had an 87% (0.13 RR (95% CI: 0.05–0.38); P < 0.05) lower OP failure rate. OP is highly effective in preventing new cases of influenza during outbreaks in ACFs, especially in ACFs with dementia or high care wards. Mandatory reporting of influenza outbreaks to PHUs would ensure that ACFs are supported throughout the outbreak, which will facilitate reductions in hospitalizations and mortality.

Rapid on‐site molecular Point of Care Testing during influenza outbreaks in aged care facilities improves antiviral use and reduces hospitalisation

“…Importantly, hospitalisations due to influenza outbreaks were significantly lower when ACFs used POCT, reducing the possibility by 43%. Although our study is small and observational, it is supported by a recent study that found antiviral prophylaxis prevented a high percentage of influenza cases during outbreaks, particularly in ACFs with high‐level care and dementia units 15 . This may be relevant to ACFs struggling to manage the threat of COVID‐19.…”

“…NSW Health recommend antiviral treatment and prophylaxis (oseltamivir) as per the Commonwealth CDNA Guidelines. Although there are multiple recognised protocols across ACFs, all suggest the implementation of antivirals within 72 hours 15 . Despite some conflicting evidence on the effectiveness of antivirals use in ACFs, more data are emerging 14 …”

“…Our findings highlight the timely use of POCT as an additional measure in ACFs that enables timely prescription of antivirals, which in turn may prevent hospitalisation. Recent findings reported that for each day an ACF delayed reporting an influenza outbreak, there was a 6% increase in hospitalisations and the duration of the outbreak was prolonged by 0.42 days each delayed day 15 …”

“…Although our study is small and observational, it is supported by a recent study that found antiviral prophylaxis prevented a high percentage of influenza cases during outbreaks, particularly in ACFs with high-level care and dementia units. 15 This may be relevant to ACFs struggling to manage the threat of COVID-19. It can be noted that ACF residents are generally frail with numerous comorbidities and live in similar conditions across facilities.…”

Epidemiology of 2017 influenza outbreaks in nine Australian Aged care facilities

“…Use of antiviral drugs such as oseltamivir, which if taken within 48 hours after the initial symptoms, can reduce disease severity and influenza‐associated complications, 10 and studies have shown impact of using oseltamivir as prophylaxis in preventing and management of influenza in the residential care facilities 11‐13 . One study reported that oseltamivir prophylaxis reduces the influenza attack rate of 90% in residents during outbreaks, particularly in high care wards 11 . Furthermore, crowded living conditions and the frequent use of common rooms favour a rapid spread of respiratory infections.…”