Why is Anti tetanus injection useless?

Answer 1

It is not. In fact it is very useful, and full blown tetanus is fairly rarely seen in developed countries.

However one problem with the vaccine is that it requires regular re-vaccination (typically every 10-years or so). People rarely do so, and are thusly rarely protected by the vaccine.

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The current vaccine schedule (in the US) is to get three shots (DTaP) in the first year of life (usually 2,4,6 mos), one more shot between ages 12-18 months and one shot before starting kindergarten. The first "booster" is given at age 11-12, and then every 10 years afterward (if you get an injury they will give an early booster if the last was more than 5 yrs ago).

As the previous poster pointed out very few adults continue to get the 10 year boosters. Despite that, we see exceptionally little tetanus in westerners who got the original series of vaccine. For that reason may have questioned whether we really need a booster every ten years throughout adult-hood and the "powers that be" have been discussing scaling back that recommendation for some time. One proposed schedule is to get the shots as above through the 11-12 yr booster and then do something like do another at age 50 and then another at age 65.

To be clear: Everyone agrees that you should be given a booster if you get a deep injury and it has been more than 5 years since your last shot. Also, every major US medical organization still recommends an update very 10 years. They are debating the change but have not yet made it.

In addition: a few years ago they discovered that a lot of nagging coughs that last a few weeks in adults are actually pertussis ("whooping cough" and the "P" in DTaP vaccines given to children). For that reason they added a booster to pertussis to the adult tetanus and it is recommended that people under the age of 65 who have not had a tetanus shot in the last 2 years get the new one, even if not normally due.