Prevalence of Anti-poliovirus Type 1, 2 and 3 Antibodies in Unvaccinated Italian Travelers

Authors


  • This work was presented in abstract form at the conference “New Challenges in Tropical Medicine and Parasitology”, 18–22 September 2000, Oxford, UK.

  • Pasteur BioMerieux provided financial support for the laboratory investigations presented in this study.

  • Apart from this, the authors had no financial or other conflicts of interest to disclose.

Reprint requests: Alberto Matteelli, Institute of Infectious and Tropical Diseases, University of Brescia, Piazza Spedali Civili, 1-25123 Brescia, Italy.

Abstract

Background Immunization against poliomyelitis is recommended for international travelers to developing countries. However, the level of antibodies varies even in previously unvaccinated persons, due to wild-type or vaccine-type infections in the eldest travelers.

Methods In 1999, we conducted a seroprevalence study in the Lombardy region (northern Italy), using sera collected in 1994 from a population aged 50 to 59 years. The study subjects were consecutive, randomly selected travelers enrolled in an anti-hepatitis A virus antibody study. Neutralizing antibodies were titrated on Vero cells in microtiter plates. Each serum dilution (1:8 to 1:256) was challenged against 100 tissue culture infective doses of the three Sabin strains. Titers> 1:8 were considered to be protective.

Results We studied 98 travelers, 59 male and 39 female, of mean age 54 years. Seventy-three (74.4%) reported previous travel abroad, but none had been vaccinated against polio. Dietary habits included consumption of seafood in 74.4% and raw vegetables from their own garden in 52.1%. The seroprevalences for neutralizing antibodies against poliovirus type 1, type 2 and type 3 were 86.7%, 89.9%, and 86.7%, respectively. All travelers presented protective antibody titers against at least one of the three viral types. Protective antibody titers were unrelated to travel history or dietary habit.

Conclusions A high proportion of the previously unvaccinated adults in our sample presented protective immunity to polioviruses. This observation may have implications for cost-effectiveness analysis of generalized polio vaccination in adult Italian travelers.

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