The feedback process conducted in 10 of the 12 main vaccinating clinics in the Quebec City region did not decrease overall vaccination delays. A high proportion of the DTaP-Polio-Hib and pneumococcal vaccines were administered before the age of three months (94%), both before and after the intervention. The proportion of doses administered without delay was lower for meningococcal (77%) and MMR (73-75%) vaccines.
Vaccination delays observed in this study are similar or compare favourably with VD documented in other countries for MMR [13
] or for vaccines containing certain elements of DTaP-Polio-Hib [30
]. Nevertheless caution must be exercised in comparing VD data given the different methodologies employed.
Several reasons could explain the low impact of the intervention conducted herein. Firstly, this was an isolated intervention not combined with other types of interventional activities. Feedback that is integrated into other activities and sustained over time, such as that inspired by the Assessment, Feedback, Incentives and Exchange (AFIX) strategy, appears to be more likely to have an impact on vaccination [20
]. Moreover, an increase in the number of doses administered in 2008-2009 was noted compared to 2007-2008. The pressure represented by this increased demand for vaccination could have contributed to the low impact of the feedback. As well, only half of the health professionals involved in vaccination in the clinics that were visited participated in the feedback process. The impact analyses, on the other hand, dealt with the totality of vaccination acts in the participating clinics, since the registry does not include a specific code for each vaccinator. Finally, VD presented were relatively low for some clinics and may not have generated sufficient motivation to change current practices. However, the feedback provided could have influenced more specific problematic practices resulting in high VD.
It is possible that the feedback was the cause of the decrease in VD observed for the four clinics that modified their practices concerning multiple injections. It is also possible that the introduction of the combined measles, mumps, rubella and varicella vaccine (MMR-V) administered at one year of age as well as the involvement of nurses in vaccination contributed to these changes. Two of the four clinics involved hired nurses or gave nurses additional responsibilities following the feedback. Other studies suggest that the involvement of nurses favours adherence to recommendations regarding vaccination [17
]. These results are important, since the practice of multiple injections is a factor that facilitates complete immunization [33
]. However, these modifications did not appear to have an impact on global analyses. A possible hypothesis is that the decrease in VD was observed in four of the smallest clinics that only gave a limited number of vaccine doses, therefore having a limited weight compared to larger clinics.
A relatively wide consensus exists concerning the definition of VD, namely one month after the date on the immunization schedule [34
]. In the present study, the results using this standard did not suggest any deterioration or improvement in VD after feedback. When using a one-week standard, we observed an increase in VD for the first DTaP-Polio-Hib vaccine, for the first pneumococcal vaccine and for the meningococcal vaccine. However, these increases in VD correspond to a mean immunization time delayed by only one or two days in the year following the feedback, a difference not clinically significant. It is possible that using a one-week definition for VD may be too sensitive to very minor changes in immunization practices and lead to misinterpretations. Furthermore, using a short one-week standard for VD could demoralize clinicians because it is very difficult to reach. This issue was reported by some participants during the feedback sessions.
In Quebec, the Ministry of Health and Social Services tracks the vaccination delays associated with DTaP-Polio-Hib, pneumococcal and meningococcal vaccines. Strict surveillance of VD for DTaP-Polio-Hib vaccine is essential, as delays in its administration are associated with incomplete VC [3
]. Since the VD for pneumococcal vaccine are almost identical to that for DTaP-Polio-Hib, and since it is scheduled for the same visit, the benefits associated with its surveillance appear rather limited.
A number of limitations of this study should be mentioned. A high proportion of vaccination acts are recorded in the vaccination registry used (VAXIN) [35
]. However, when children move to the Quebec City region, it is possible that vaccines given previously in other regions may not be systematically reported and recorded. This phenomenon is apt to lead to an overestimation of VD, but should be consistent over time. The fact that the VD determined by this study are close to the data reported in provincial studies is nevertheless reassuring [3
The questionnaire was completed in person after the first observation period and by telephone after the second observation period. As well, the same person was reached in only five of the ten clinics. An effort was made to limit the impact of this latter factor by formulating the questions in the same manner.
Finally, the use of a control group would have allowed for the impact of the feedback to be better identified. However, such a strategy would have been extremely difficult to apply since a large majority of doses are administered by a small number of clinics in the Quebec City region and the clinics that vaccinate the most were the ones that participated in the study. Nevertheless, we compared the VD observed during the two periods for those clinics that did not participate in the project and the same tendencies were noted.