the meta study i mentioned earlier basically ahows that herd immunity is a myth, that in fact is oe of the conclusions of the study. if the difference between those that get a shot and those that don’t catching the flu is only 4%, the whole herd immuinty concept for the flu shot is shot down in flames.
Herd immunity works if the threshold limit for immunity reaches a set point for the specific disease. For polio, 80 to 86% of the population needed to be immune before herd immunity occured. Pertussis requires up to 94%. Herd immunity for a virus such as the flu which keeps mutating is a moving target and is probably not even calcuable. The present vaccine is stated to be 63% effective. That figure can change as the virus mutates. There are also people who have natural immunity, an unknown percentage. There is also community immunity, which if you are a vulnerable person, did not get the flu shot, surrounded by people who don’t have the flu or won’t get it, you won’t get it either.
When they get a vaccine that can block all flu viruses, which they are working on at this time, flu will have a set percentage for herd immunity just like other diseases.