The control of vaccine preventable diseases is one of the major advances of public health 1 . Although immunisation uptake is high for most routine immunisations in western countries, yet high risk groups, including children with underlying diseases, have often low immunisation coverage 1 . Chronic diseases such as neurological and cardiovascular disorders are associated with high hospitalisation rates 2 3 , and some immunisations including influenza and conjugate pneumococcal vaccines may prevent admission into hospital, medical visits, and other negative effects in these patients 4 5 . Despite mathematical models suggest that focusing immunisations on high risk groups may be suitable 6 7 , parents of children at risk may underestimate incidence and severity of vaccine preventable diseases and may not be appropriately informed about safety and efficacy of available vaccines 7 8 9 10 . Moreover immunisation delays often occur because of false contraindications linked to an underlying condition that, on the contrary, may represent an indication to immunisation 10 11 12 . Immunisation rates are usually monitored by immunisation registries 13 ; in the U.S. vaccine delivery is shifting from the public sector to the private sector, with an emphasis on vaccination in the context of primary care and the medical home 14 . Patients with chronic diseases may refer to private providers, that often do not submit data to a national or regional registry 13 15 . The reasons leading parents to choose a private practice for immunisation have not been well studied yet. This study aims, primarily, to describe the characteristics of two populations attending a private or a public immunisation service in the same metropolitan area. Secondarily this study has the objective to determine if the prevalence of patients with chronic diseases by type of service differs, and to study if the choice of different providers is associated with timeliness in immunisation.

A total of 202 parents of children 2–36 months of age were interviewed, 104 (51.5%) in the public office, and 98 (48.5%) in the hospital practice. (Figure 1a,1b).

The general features of parents interviewed and their children in the two groups are shown in Table 2.

Although several characteristics of parents and children seen in the two practices were similar, foreign parents and graduated mothers were more represented in families who requested immunisation in the public service, whereas families interviewed in the hospital practice had more frequently firstborn female children to be vaccinated, who were breast fed for a longer period, who had a lower birth weight, and who were more frequently hospitalised in the previous period.

The overall immunisation coverage for influenza vaccine was 1.9% (2 patients) in children in the public office and 1.0% (1 patient) in those immunised in the hospital practice (P = 0.52). Immunisation with conjugate pneumococcal vaccine was administered to 70 (67.3%) children in the public practice and 63 (64.0%) in the hospital office (P = 0.65), whereas 59 (56.7%) of them in public service and 49 (50.0%) in hospital office were immunised with conjugate meningococcal C vaccine (P = 0.33). Finally, none of the children in the public practice and 5 (5.10%) in the hospital office were immunised against varicella vaccine (P = 0.02)

Nine (9.2%) out of the 98 patients immunised in the hospital had an underlying disease which was an indication for influenza, pneumococcal, and meningococcal C immunisation. Out of them only 1 child was immunised against influenza; 6 against pneumococcus, and 4 against meningococcus C at the time of the interview. Underlying diseases included: three cases of congenital heart disease, two cases of a neurological disease, and one case of a genetic syndrome. None of the children immunised in the public service had an underlying disease (P = 0.001).

The Italian Ministry of Health also recommends influenza immunisation of households of patients belonging to risk groups 20 . Among the parents of these children only 2/9 mothers and 4/9 fathers received influenza immunisation.

Although the number of children with an immunisation delay was substantial in both practices, they were nearly twice in the hospital practice than in the public service (DTP, polio, HBV, and Hib: 39.8% vs 22.1%; P = 0.005; MMR: 20.0% vs 12.5%; P = 0.15). Causes of delayed or missing immunisation reported from parents were mostly related to misinformation (58%), and child illness (15.6%).

Determinants of delayed immunisation was studied through a logistic regression model (Table 3). The univariate analysis showed that a lower education of parents, a low birth weight, and immunisation in the hospital predicted an immunisation delay, but none of these variables were significant in the multivariate model. None of the variables included in the analysis were associated as well with delay of MMR immunisation, while children with a father from a foreign country were more likely to receive pneumococcal immunisation (OR: 3.18; 95% CI: 1.08 – 9.42).

This study shows that children with underlying diseases, which often represent an indication to certain immunisations, were more likely to attend the hospital immunisation provider rather than the public office of their own district.

Families of children with low birth weight preferred more often immunisation in the hospital and were more likely to be immunised against influenza. Parents who chose to immunise their children in the hospital have the perception of hospital as a safer environment; this finding underlines how lack of information or misinformation and the perception of an underlying disease as a contraindication, play a substantial role in the choice of health care providers and inappropriate consultation.

Despite recommendations in place, coverage for immunisations indicated in high risk groups is low in our country 18 19 . Other studies performed in hospital settings and on high risk group children showed that immunisation coverage among these groups remains low and immunisations are often delayed. 21 22 23 24 25 26 27 28 .

We found that families of children with immunisation delay attending the hospital practice had often previously attempted to vaccinate their children. This observation underlines the potential to improve immunisation timeliness through simple information and educational activities.

Different approaches have been proposed for overcoming immunisation barriers in high risk groups. There is evidence that enhanced information focusing on vaccines benefits and how to manage their potential adverse effects, increased availability of vaccine offices, use of missed opportunities, and gratuity of immunisation are efficacious in increasing immunisation uptake 11 12 13 .

We also observed that being immunised in a hospital setting was a predictor of delayed immunisation for routine vaccines. We speculate that this finding may be associated with misinformation and false contraindications, and it is in line with the frequent parents' perception of hospital as a safe environment.

Regarding the determinants of appropriateness of immunisation we did not find significant associations with any of the variables included in the analysis. However the study may have not been adequately powered to address this issue. Nevertheless, we found a signal toward an association between an higher education of parents and timeliness of immunisation.

Although the number of vaccinees may be small in a private hospital practice, this finding underlines how offering immunisations indicated in high risk groups in a hospital setting may result in a significant benefit. Hospitals are likely to attract high risk groups which often are immunised late.

One advantage of this study was the inclusion of different immunisation settings serving the same population although these results are not necessarily generalizable to other settings. Our findings show that an integration between public and hospital settings, and an effort to improve communication on vaccines to parents, may significantly increase immunisation rates in high risk groups and in the general population and prevent the delays in immunisation.

The authors declare that they have no competing interests.

All Authors participated to the design and coordination of the study and helped to draft the manuscript. All authors read and approved the final version of the manuscript.