Antipoliomyelitis immunity status in a cohort of young men drafted into military service, residing in the suburban Milan area

PREVALENCE OF NEUTRALIZING ANTIBODIES AGAINST POLIOVIRUS 1, 2, AND 3 IN HEALTHCARE PROFESSIONALS AGED 20-50 YEARS

Objective:

To describe the prevalence of neutralizing antibodies against poliovirus (PV1, PV2, and PV3) in blood samples of healthcare professionals aged 20 to 50 years.

Methods:

Health professionals who serve children at Darcy Vargas Children’s Hospital and the Department of Pediatrics of Irmandade da Santa Casa de São Paulo. The sample size was calculated at 323 participants. The Mantel-Haenszel chi-square was used to verify differences between groups. The neutralization reaction detected human poliovirus antibodies. For susceptible individuals, vaccination with the inactivated+triple acellular polio vaccine was performed, and neutralizing antibodies were re-dosed after one week.

Results:

333 professionals were studied - 92.8% were immune to poliovirus 1, 86.5% to poliovirus 2, and 63.3% to poliovirus 3; 37% had titers less than 1:8 for any serotype, 5;1% had titers below 1:8 for all three. Vaccination with inactivated polio vaccine was performed for susceptible participants, and neutralizing antibodies were dosed after one week, showing increased titers for all polioviruses.

Conclusions:

Despite the detection of a significant percentage of individuals with low poliovirus antibody titer, the challenge with vaccination demonstrated immune response compatible with poliovirus immunity.

Is EU/EEA population protected from polio?

The WHO European Region has been declared polio-free since 2002. By 2010, inactivated polio vaccine (IPV) was the only polio vaccine in use in the EU/EEA for the primary vaccination of children. A systematic review of the literature on polio seroprevalence studies, complemented by the analysis of available vaccine coverage data, has been carried out with the aim of assessing the level of protection against polio in the European population. A total of 52 studies, with data from 14 out of the 31 EU/EEA countries, were included in the analysis. This systematic review shows that, overall, seroprevalence for PV1 and PV3 is high in most countries, although seroimmunity gaps have been detected in several birth cohorts. In particular, relatively low immunity status was found in some countries for individuals born in the 60's and 70's. Discrepancies between reported vaccination coverage and immunity levels have been also highlighted. Countries should make sure that their population is being vaccinated for polio to reduce the risk of local poliovirus transmission in case of importation. Moreover, assessing immunity status should be priority for those traveling to areas where wild polioviruses are still circulating.

Serological survey on immunity status against polioviruses in children and adolescents living in a border region, Apulia (Southern Italy)

BACKGROUND

In 1988 the World Health Assembly adopted the goal to eradicate poliomyelitis by routine immunization using Oral Polio Vaccine (OPV). On 21 June 2002 the WHO European Region was declared polio-free. In 2008 poliomyelitis is still endemic in 4 countries (Nigeria, India, Pakistan, and Afghanistan), where 1201 new cases were registered in 2007; 107 sporadic cases were also notified in countries where poliovirus is not endemic. The aim of this work was to verify the level of antipoliomyelitis immunity status in children and adolescents in the Apulia region (south of Italy), which may be considered a border region due to its position.

METHODS

704 blood specimens from a convenience sample were collected in six laboratories. The age of subjects enrolled was 0-15 years. The immunity against poliomyelitis was evaluated by neutralizing antibody titration in tissue culture microplates.

RESULTS

Seropositivity (neutralising antibodies titre > or = 8) for polioviruses 1, 2 and 3 was detected in 100%, 99.8% and 99.4% of collected sera. Antibody titres were not lower in subjects who received either four doses of inactivated polio vaccine (IPV) or a sequential schedule consisting of two doses of IPV and two of oral polio vaccine than in subjects who received four doses of OPV.

CONCLUSION

These results confirmed current data of vaccine coverage for poliomyelitis: during the last ten years in Apulia, the coverage in 24 months old children was more than 90%. The high level of immunization found confirms the effectiveness both of the sequential schedule IPV-OPV and of the schedule all-IPV. Apulia region has to face daily arrivals of refugees and remains subject to the risk of the importation of poliovirus from endemic areas. Surveys aimed at determining anti-polio immunity in subpopulations as well as in the general population should be carried out.

Seroprevalence to polio in personnel at a virology institute

OBJECTIVES

To determine the level of immunity to polio in adult personnel at the National Institute for Virology (NIV), South Africa.

METHODS

Polio neutralizing antibodies results on 776 NIV staff members tested between 1979 and 1999 and seroresponses in seronegative personnel given a booster vaccination were analysed.

RESULTS

613 of the 776 (79%) personnel had neutralizing polio antibodies to all three types, independent of age, gender, race or job category. Types 1 and 2 antibodies were found in 92% and 94%, respectively, but type 3 was less prevalent at 87%. Of the 93 persons seronegative to one or more types, 13 failed to respond to the first booster vaccination and 8 remained as non-responders after two booster vaccinations. Of the 19 personnel who were bled four days after booster vaccination, 16 (84%) had already developed an antibody response.

CONCLUSIONS

Most (79%) adult laboratory personnel retained detectable levels of neutralizing antibodies to polio, independent of age, gender, race or job category, and even in those persons lacking detectable antibodies, most (84%) responded with a secondary immune response. Nevertheless the immunity gap, particularly to type 3, mandates routine screening of personnel potentially exposed to wild-type polio virus and a booster vaccination for seronegatives.