If I cut my finger whilst gardening should I get a tetanus vaccination?

The short version: for a clean cut from gardening, a tetanus booster is very unlikely to be needed if you have had a primary series, and the evidence shows a single booster works even decades later.

The core question is whether the wound is tetanus-prone. A clean cut from gardening tools, without deep puncture, devitalized tissue, or soil contamination, is a low-risk wound. The evidence on tetanus immunity is clear: a 1984 study of Danish adults found that among people with documented primary vaccination who had not been revaccinated in over 25 years, only 28% had fallen below the protective antibody level [2]. And a single booster dose brought every single one of them back above 1 IU/ml, far above the protective threshold [2]. A 2015 study showed that 10 years after a booster, 87% of young adults still had protective tetanus antibody levels [1]. So if you completed the childhood series, your immunity is likely still adequate, and if it is not, one shot will restore it.

The risk of the vaccine itself is not zero. The tetanus toxoid is an aluminum-adjuvanted injection [2], and like all such injections, it can cause local inflammation, fever, and in rare cases more serious immune reactions. The 2015 study reported that a decennial booster was well-tolerated, but the safety data came from a manufacturer-funded trial [1]. The long-term effects of repeated aluminum adjuvant exposure on immune balance and colloidal stability are not studied in these records. The burden of proof for injecting you today falls on the people recommending it, and they have not shown that the benefit of a booster for a clean cut outweighs even the small risk of the injection.

My call: if you had the childhood series, you do not need a booster for a clean gardening cut. If it has been more than 10 years since your last booster and the wound is deep or dirty, a single booster is reasonable. Confidence: moderate, because the evidence on immunity persistence is strong [2][1], but the evidence on the net benefit of routine decennial boosting for low-risk wounds is thin and comes from conflicted sources.