Uptake of pneumococcal conjugate vaccine: methodological issues in measurement and impact of publicly funded programs

In Quebec, the pneumococcal conjugate vaccine was available on the private market as early as 2001 and has been included in the publicly funded immunization program since December 2004.

To compare the advantages and limitations of two different sources for assessing vaccination coverage in the target population of children and to evaluate the impact of the public health program on uptake rates.

Data from a province-wide survey of a random sample of parents and from the Quebec City Immunization Registry were used to compute vaccination rates over time in different population groups.

Data from the immunization survey and the regional registry were congruent regarding trends. Immunization rates were overestimated, more in the registry than in the survey. During the 2001-2004 period, uptake rates were low, and many children received fewer than the recommended number of doses. As soon as free vaccination was granted, uptake increased markedly and close to 90% of children received the recommended three doses, the level required for inducing herd effects. Delay in the administration of the third booster dose was observed.

Free vaccination is a major determinant of vaccine uptake and should remain a fundamental principle of the Canadian health system.