Reply letter to "Immunogenicity and safety of a quadrivalent high-dose inactivated influenza vaccine compared with a standard-dose quadrivalent influenza vaccine in healthy people aged 60 years or older: a randomized Phase III trial".

A recent study reported that the high-dose quadrivalent influenza vaccine provided superior immunogenicity and efficacy versus the standard-dose quadrivalent vaccine in the elderly. However, we need to view these results in terms of public health benefits as well. The Number Needed to Vaccinate (NNV) is an important tool to measure the benefit of a given vaccine. Further, NNV evaluates the benefits of a vaccine in preventing and controlling communicable diseases. Considering the target of vaccination and coverage of 75% not met in the elderly in Europe, it is important not to prioritize one vaccine over the other, but rather to increase the vaccine coverage with all the available vaccines.