Poliovirus neutralizing antibody persistence after vaccination with the Sabin vaccine: a follow-up study.

In 1976, a cohort survey on the persistence of neutralizing antibodies in children regularly immunized 1 to 4 years earlier with the Sabin attenuated vaccine (OPV) was undertaken in the Venice mainland. Subsequent serological evaluations in the same cohort were carried out in 1983 and 1993. A macroneutralization test using a 1:4 initial serum dilution was utilized in the 1976 and 1983 survey years. In the 1993 survey a microneutralization test using a 1:2 initial dilution was utilized. In this survey, however, sera were tested using both the latter microneutralization test and the former test. Using the former method, the results indicate that the OPV-induced humoral immunity to poliovirus 1 and 2 remain fairly stable after the initial decrease, whereas antibodies to poliovirus 3 are further declining. Using the latter more sensitive method the seropositivity rates were found to be equal or close to 100 percent. The results of our follow-up survey thus indicate that the OPV-induced humoral immunity is long-lasting when tested with a highly sensitive and reproducible method. The clinical protection that ensues after OPV-immunization is probably lifelong similar to that which follows the natural infection.

Immunity status to poliovirus in Veneto region (north-east Italy). A seroepidemiological survey.

The immunity state to poliovirus types 1, 2, and 3 of a population aged 2 to 75 years was determined by examining 274 sera collected in the Venice mainland (North-East Italy). Altogether, the neutralizing antibody prevalences (at a titre > or = 1:2) for poliovirus 1, 2, and 3 were 99.0 percent (geometrical mean titres [GMT]: 72.1), 99.6 percent (GMT: 95.9) and 98.2 percent (GMT: 17.3), respectively, and all the age groups also showed very good levels of humoral immunity. High antibody titres (> or = 1:256) to one or more types of poliovirus were demonstrated in older age groups also, possibly indicating exposure to natural polioviruses or contact with vaccine strains. Although probably all the older subjects had practically acquired their antibodies as a result of natural infection and those under 30 through vaccination, these results indicate that the humoral immunity against poliomyelitis in our population is satisfactory, and the maintenance of such good protection level depends on an effective immunization program.

Persistence of poliovirus-neutralizing antibodies 2-16 years after immunization with live attenuated vaccine. A seroepidemiologic survey in the mainland of Venice.

A seroepidemiological survey was conducted on subjects who had received a full vaccination course with live attenuated poliovirus 2-16 years before. For strains 1 and 2 prevalence of seropositives and median values dropped gradually during the first 10 years; strain 3 showed a much earlier decline. Environmental displacement of wild poliovirus by the attenuated, less immunogenic strain might eventually induce a 'gap', should complacency hamper needed vaccination efforts.

Prevalence of poliovirus neutralizing antibodies. A seroepidemiologic survey of vaccinated and unvaccinated women of fertile age.

The Authors tested a group of 232 women of fertile age, living in the Venice mainland, for presence of detectable protective serum antibodies against poliovirus strains 1, 2 and 3, according to vaccination status with living, attenuated poliovirus. Overall, unvaccinated subjects had a slightly higher prevalence of seropositivity as well as higher geometric mean titres than the women who had undergone a full vaccination course fifteen to twenty years before. Particularly worrisome was lack of protection against poliovirus 3, found in 23% of vaccinated and 15% of unvaccinated study participants. Break in herd immunity might end up in localized outbreaks of poliomyelitis, a not too distant possibility in Italy, where a steady flow of immigrants from North Africa and the Near East provide a source of wild poliovirus strains.

Hepatitis B vaccine: immune response in student nurses. A fifteen-month follow-up.

The authors describe a 15-month follow-up of twenty-nine nurse students vaccinated against hepatitis B with Hevac B Pasteur. At three months all subjects were anti-HBs positive, with a geometric mean titre (GMT) of 1187 mIU/ml. At the time of booster dose (T14) GMT had fallen to 380 mIU/ml; after one month (T15) GMT had risen again to 9332 mIU/ml. Such a high antibody level suggests a long lasting protection.

Transmission of non O group 1 Vibrio cholerae by raw oyster consumption.

After having eaten dinner many customers of a restaurant in Dolo (Venice) developed gastroenteritis with diarrhoea and vomiting. Strains of non O group 1 Vibrio cholerae were isolated from rectal swabs of four customers. Epidemiological investigations revealed an association between the illness and raw oyster consumption (p = 0.008). Also, an association was found between age and illness among males (p = 0.034). As a consequence of this outbreak, a gastroenteritis surveillance programme was run for three months by health authorities in the Regione Veneto. The results indicate that, although non 0-1 V. cholerae does not account for severe pathology, it causes mild gastroenteritis and asymptomatic infections in developed countries.