Introduction and objective:
Vaccination is the most effective and reliable strategy for preventing the morbidity of tetanus. The aim of the study is to investigate the seroprevalence of antibodies to tetanus toxoid among healthy persons across all age groups to determine the level of vaccine-induced immunity in the population, and to identify which age group should be targeted for a booster dose.

Material and methods:
A total of 2,842 serum samples collected between 2010 – 2019 from individuals aged from 1 month – 97 years were investigated. Anti-tetanus IgG antibody concentrations (IU/ml) were measured by an enzyme-linked immunosorbent assay. In addition, the avidity of antibodies was determined using an in-house ELISA.

Results:
The results showed that among the 2,842 individuals, 147 (5.2%) had anti-tetanus toxoid IgG antibody levels below 0.1 IU/ml and another 1,519 (53.4%) subjects showed only basic protection (0.1–1.0 IU/ml) and needed immediate booster. High levels of anti-tetanus toxoid IgG antibodies (>1.0 IU/ml) were found more often in young adults at the age 21–40 years (55.5%, GMT=1.15). Importantly, these antibodies also had the highest avidity. With age, the percentage of high positives decreased, as well as the geometric mean and avidity of antibodies, reaching the lowest level in subjects over 70 years of age (13.3%; GMT=0.19). Characteristically, a higher percentage of high positive results was observed in men (42.6%) than in women (34.3%).

Conclusions:
The study showed adequate immunity levels to tetanus amongst the Polish population, especially in children, adolescents, and young adults. However, those from older age groups should receive booster doses of the vaccine.