Advance planning and preparedness help mitigate the impact of future pandemics. Risk assessment is critical to decide, clarify and justify public health preparedness, response and recovery actions. The Tool for Influenza Pandemic Risk Assessment (TIPRA) is used to assess the pandemic risk of influenza viruses with pandemic potential.

The objectives are to:

• support a timely and updatable hazard risk assessment for influenza viruses with pandemic potential;
• transparently document features of the viruses and the infections they cause that might pose threats to a human population;
• identify knowledge gaps and prompt further investigations including research and surveillance;
• facilitate information sharing between scientists, policy-makers and other stakeholders.

The launch of TIPRA 2nd edition was in April 2020. The scope and calculation process of an overall risk in TIPRA 2nd edition have diverged from TIPRA 1st edition. First, the 1st edition was designed for use on a novel influenza virus which has caused at least one human infection. The 2nd edition enables risk assessment of animal influenza viruses that have not caused human infection but are still of public health importance. Second, the 1st edition employed a gateway approach based on set levels of population immunity to determine viruses with pandemic potential. The 2nd edition removed this gateway approach and instead included Population Immunity as two separate risk elements weighted in likelihood and impact bringing the total number of risk elements to 10 in the 2nd edition, versus 9 in TIPRA 1st edition. Third, the ranking and weights of TIPRA 1st edition risk elements were revisited and changed. Overall, likelihood and impact scores between 1st and 2nd edition would be different; 9 elements in the former and 10 elements in the latter. However, the relative pandemic risk of different viruses to each other is expected to remain similar. Furthermore, TIPRA technical experts (TE) reviewed individual risk elements definitions and criteria of TIPRA 1st edition. The definitions and criteria provide specificity to the risk elements so that TE can operate from a common understanding when making point estimates within the numerical scale of risk for each risk element under consideration. The TIPRA TE representing each risk element generated revision and established a final consensus version through discussion and debate. Each risk category in individual risk stratifications were refined in the 2nd edition to reduce the scope of subjectivity and minimize the score variations.