Monitoring seasonal influenza vaccine safety in Australia: a proactive, collaborative approach

Researchers from AusVaxSafety, the Therapeutic Goods Administration (TGA) and the The Kids Research Institute Australia have detailed the cooperative efforts and systems in place to monitor the safety of seasonal influenza (flu) vaccines in Australia, in a recently published Medical Journal of Australia commentary.

Each year, millions of people in Australia choose to receive a seasonal flu vaccine to ensure they are optimally protected for the flu season ahead.

Given the high number of flu vaccines administered yearly, as well as annual vaccine formulation changes to cover new flu strains, there is a strong need for ongoing post-market vaccine safety monitoring to ensure vaccines are performing as safely as expected.

Complementary surveillance systems with a common goal

Australia’s vaccine pharmacovigilance – the monitoring, detection, investigation and actioning of vaccine safety signals – is underpinned by two key systems: the TGA’s vaccine surveillance system and AusVaxSafety.

The two systems operate in tandem to monitor for unexpected types and rates of adverse events following immunisation (AEFI) – including rare and population-specific events – to enable rapid identification and timely investigation of any potential safety concerns.

TGA seasonal influenza vaccine pharmacovigilance

The TGA collects reports of AEFI from healthcare professionals, pharmaceutical companies, state and territory health departments, and the general public. Information from these reports – which are coded using the standardised Medical Dictionary for Regulatory Activities (MedDRA) – is made publicly available through a national database.

The TGA reviews individual cases and convenes a Vaccine Safety Investigation Group when an AEFI of concern that has the potential to change the favourable benefit–risk balance of a vaccine or affect public confidence in vaccine safety is identified.

To identify potential safety signals, the TGA uses data‐mining algorithms to interrogate its database to identify AEFIs that have a higher number of reports than expected for particular vaccines. The TGA may also investigate potential signals based on interagency communication (including with AusVaxSafety); meetings with state and territory health authorities, international regulators and pharmaceutical companies; and from published literature.

During the flu season, the most frequently reported AEFIs and adverse events of special interest are analysed and reported monthly.  

AusVaxSafety seasonal influenza vaccine pharmacovigilance

AusVaxSafety has undertaken national active surveillance of seasonal flu vaccine safety since 2014.

To do this, AusVaxSafety distributes a short online survey via SMS or email to flu vaccine recipients three days after vaccination at participating AusVaxSafety sites – which include general practices, pharmacies, Aboriginal Community Controlled Health Organisations and hospitals across Australia.

The survey allows participants to report any adverse events they may have experienced following seasonal flu vaccination. Deidentified survey response data undergo signal detection analyses via two complementary statistical methods that allow for comparison if a signal is detected.

The results of these analyses are reported to the Australian Government Department of Health, Disability and Ageing – including the TGA – and state and territory health departments and contribute to Australian pharmacovigilance investigations of any potential safety concerns.

Summaries of adverse event data are also reported to the public on the AusVaxSafety website. 

Challenges of national pharmacovigilance systems

Australia’s vaccine pharmacovigilance systems face ongoing challenges in flu vaccine signal detection and investigation.

The TGA system relies on passive, spontaneous AEFI reports, and data captured therefore may suffer from under-reporting and reports that are incomplete, due to factors such as level of reporting knowledge, reporting system access and perceived importance of reporting.

Concurrent active surveillance conducted by AusVaxSafety helps mitigate these issues by prompting individuals who have received a vaccine to report any AEFIs. However, the quality of self-reports and the potential for missing data can impact safety signal detection and investigation.

Long-term or late-onset reactions pose additional challenges for pharmacovigilance systems and are not captured in active surveillance surveys. Their detection requires clinicians and individuals to be vigilant and consider the possible involvement of vaccines in chronic or late-onset conditions and subsequently report them to the TGA.

While spontaneous surveillance has its limitations, it remains effective in rapidly detecting safety signals, promoting regulatory actions and updating flu vaccine product information.

The future of seasonal flu vaccine pharmacovigilance in Australia

Continued investment in Australia’s vaccine pharmacovigilance systems, coupled with public education and provider engagement, is required for ongoing success.

Efforts to enhance AEFI data capture, quality and completeness are in progress, while targeted education modules are also being developed and deployed to further boost healthcare provider awareness and engagement with AEFI reporting.

Databases used for these data are also undergoing updates to provide better functionality and more streamlined data exchange.

The TGA and AusVaxSafety recognise the importance of providing timely and transparent information on seasonal influenza vaccine safety to the Australian public.

Close collaboration between national pharmacovigilance systems continues to support the health and safety of people in Australia through close monitoring of seasonal influenza vaccines and rapid communication of any emerging safety signals.