The duration of tetanus antibodies varies under two scenarios. The first is passive immunity, which is achieved through injections such as tetanus antitoxin or tetanus immunoglobulin. The duration of immunity provided by these injections is relatively short. Typically, tetanus antitoxin lasts about four days, while tetanus immunoglobulin can last up to three weeks. After this period, the levels of antibodies gradually decrease, and the body may no longer be protected. Therefore, a single application of tetanus antitoxin or immunoglobulin does not provide long-lasting immunity. The second scenario involves antibodies produced by active immunity, generally through the injection of a vaccine made from attenuated tetanus bacilli. Antibodies usually start to develop about ten days after vaccination, with levels gradually increasing over two to three months and remaining high. This type of immunity lasts up to about ten years, but it is not lifelong. Regular boosters, guided by relevant tests, are required to maintain immunity.