Influenza vaccination: policy versus evidence

Protection from disease versus disease severity

Jefferson writes that it is impossible for a vaccine that does not prevent influenza to prevent its complications, including admission to hospital.1 This is clearly wrong.

It is well known that immunity induced by some vaccines (and also by some natural infections) does not necessarily protect against (re-)infection. Immunologists distinguish between so called sterilising immunity, which completely prevents replication of an intruding virus, and “non-sterilising” immunity, in which replication of the pathogen can still occur, but its spread and thus induction of disease symptoms may be reduced. To prevent severe forms of disease and the likelihood of complications such as secondary infections can be a meaningful objective for a vaccine, even though the vaccine may not be able to protect against infection and milder forms of the disease. The author's misjudgment as expressed by the cited statement makes me wonder about the plausibility of his interpretation of the existing data.