“And some like like flu vaccines show no benefit. “
Actually, the flu vaccine does show benefit. Where do you get your information that it doesn’t?
More succinctly:
http://summaries.cochrane.org/CD001269/vaccines-to-prevent-influenza-in-healthy-adults
“The preventive effect of parenteral inactivated influenza vaccine on healthy adults is small: at least 40 people would need vaccination to avoid one ILI case (95% confidence interval (CI) 26 to 128) and 71 people would need vaccination to prevent one case of influenza (95% CI 64 to 80). Vaccination shows no appreciable effect on working days lost or hospitalisation.”
The benefit claimed from flu vx is the antibodies in the blood of the person 2 plus weeks after being vaxed.
There has never been a study done of large studies of populations both vx’ed and non-vx’ed, to see if they got flu or not. Even a simple uneducated layman such as myself can see how such a study could be done easily. But for some mysterious reason, neither the CDC and other medical institutions like the NIH, or pharmaceutical companies, seem to want to do that study.
So until that happens, it’s really up in the air.
Plus, at best the flu vx is, according to vx manufacturers, 70 to at very best 80% effective - based solely on antibody response in people who got vxed; not by studying whether vx’ed people got flu or not. Also their percentage of utility of vaccine is whether the three strains of flu (most flu vx’s are trivalent) wind up being a good match for the flus that arrive.
Since the flu vx is formulated months before flu season, the CDC tries to figure out (”guesses”) which flus will be circulation in 6 or more months, and uses those strains. Flu viruses mutate promiscuously, and very often the vx winds up not being a good match for the yearly flus.
There is also some evidence from a Canadian study done last year, IIRC, that getting vx’ed over and over can cause the person to get flu more severly. If I have time I’ll try to find that.
So it is a grey “science” at best. And makes a ton of $ for the manufacturers. Interesting to note that the last head of the CDC, Nancy Cox, when she left, went to head up Merck’s vaccine division. Nice revolving door.