Our study showed a lack of immunity against rubella among Apulian young adults from 18 to 26 years of age; in this age group the proportion of susceptible subjects is more than 20%, in the other age groups the rate accounted 10-12%. The subjects with lack of immunity were born between 1988 and 1994, but only people born between 1990 and 1996 were a target of the 2003/2004 catch-up vaccination campaign planned by 2003 PNEMoRC.
A great proportion of young individuals showed lower levels of protective immunity, probably because they missed out on vaccination in catch up programmes. In fact, current coverage data for Apulian catch up target cohorts were around 70% . This coverage determined a reduction in the circulation of wild-type infection, that could cause a lack of immunity among young adults and an increase of median age of infection.
PNEMoRC also recommended the free of charge offer of MMR vaccine to all susceptible females in childbearing age, but no specific actions for the active offer took place in Italian regions. The vaccination strategy based on passive offer seemed not consistent with the PNEMORC objective to reduce the percentage of susceptible females <5% .
Considering all enrolled females in childbearing age (18-49 years), the percentages of immune subjects is of 82.3% (95% CI = 77.9-86.2).
Our results quite differ from other studies carried out in countries that implemented Universal Mass Vaccination Program. In Australia, a serosurvey performed in 2001 (3 years after the beginning of Australian Measles Control Campaign) showed that the percentage of 16-39 years old subjects immune for rubella was 97% . A similar rate was reported in the Netherlands where the rubella vaccine was actively offered to 11-years adolescents since 1974 and in 1987 the MMR vaccination was implemented in the national immunization program. In fact a 2014 survey showed a seroimmunity rate >90% among subjects aged >18 years . In these countries national immunization campaigns reached target immunization coverage.
Our regional situation seems to remind the situation of USA in 1988-1994, when a serosurveillance study reported a rubella susceptibility rate of 22% among subjects of 18-24 years old . Similarly to USA data, our results indicate the interaction between the immunization program and the natural history of rubella. In fact, in USA the rubella immunization program began in 1971 while in Italy in 2003, both the two studies were carried out 10-15 years after the beginning of immunization programs and results are globally concordant.
Bechini et al. carried out a serosurvey about rubella in Tuscany in 2012 and seroprevalence in this study (that involved a bigger number of females) is higher than in our survey, achieving 90%; this difference could be related to the enrolment of younger subjects (<18 years), that we did not consider in our sample .
The lesson learned is that in the elimination era too many women of childbearing age are still unprotected from rubella and this is consistent with the observation of some cases of CRS in Apulia in the last few years . This could be related to low vaccine acceptance, which is lower mostly in the first years after the introduction of new vaccines, to insufficient management of vaccination strategies and to inappropriate perception by general population and health care workers of the risk of vaccine-preventable diseases .
In this scenario, the public health efforts should be oriented to catch-up activities in order to reduce the rate of susceptible young adults, above all women of childbearing age. Gynaecologists and General Practitioners should be encouraged to actively propose the rubella screening among women of childbearing age before they become pregnant, in order to identify those who lack rubella antibodies, whether acquired as the result of vaccination or natural infection.
The childbearing age susceptible women immunization is indeed a priority to be pursued in all possible occasions, especially in the postpartum days and for immigrant women. Rubella vaccination should also be administered in the hospitals before the patient discharge and the recommendation to get the rubella vaccination should be reported in the dismissal letter when it is not possible to vaccine during the hospitalization. Another opportunity to check rubella immunity status of the mothers is the access to the vaccination service for their own child immunization and health care workers should be encouraged to suggest mothers to investigate their immunity status during the pre-vaccination interview.
Finally an active surveillance based on laboratories that perform rubella immunity test should be planned; laboratories should notify to Public Health Authority every woman in childbearing age with a negative test and Public Health Authority should active propose to these women the immunization against rubella.
Future studies should investigate the effectiveness of this actions to reduce the rubella susceptibility rate among young women and decrease CRS, theorized in national and international recommendations, but actually not largely implemented.