What polio antibody titer is considered protective and what revaccination regimen should be used if the titer is below that threshold?

A polio antibody titer of 1:8 or higher is generally considered protective; if the result is below that threshold, the patient should be revaccinated with inactivated poliovirus vaccine (IPV). The standard adult IPV regimen is 0.5 mL given intramuscularly, with two doses administered one month apart; a third dose can be added six months after the first if a complete series is needed. After completing the series, a single booster dose is recommended at least four years later, especially for those at increased risk of exposure. If the patient is immunocompromised or cannot receive IPV, a dose of the combined diphtheria‑tetanus‑pertussis‑polio (DTaP‑IPV) vaccine may be used as an alternative. Routine serologic testing is not required for most individuals, but if a titer is requested for occupational or travel reasons, the same protective cutoff applies and the same revaccination strategy should be followed when the titer is insufficient.