Canadian Immunization Guide
Seventh Edition - 2006

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Part 1
General Guidelines

Principles of Vaccine Interchangeability

This chapter provides the health care provider with an overview of the general principles of vaccine interchangeability for the currently approved vaccines in Canada.

The principles of interchangeability are only applicable to vaccines with the same indication and specified for the same population (i.e., the same age groups). It has now become routine to have similar vaccines from different manufacturers approved for use in Canada. Several factors may necessitate giving different products to the same individual over time. When faced with vaccine shortages, deferring vaccination is not desirable: one study demonstrated that 25% of children whose vaccination had been deferred never returned for the indicated vaccine.

Factors to consider in determining potential candidate vaccines for interchangeability

• The vaccines should be approved with the same indications, specified for the same population and be equally acceptable in terms of safety, reactogenicity, immunogenicity and efficacy.
• A regularly scheduled primary or booster vaccine should not be deferred because of the lack of availability of a particular product.
• Any new regimen should be equally acceptable from a safety, efficacy and scheduling perspective.
• Even when vaccines are approved for the same indications, different manufacturers often use different production methods, antigen concentrations, stabilizers and preservatives. Each of these could affect the immunogenicity, safety or efficacy profile of the product.

Interchangeability following provincial variations in immunization schedules and products

• At present, the immunization schedules as well as the specific products used may vary across the provinces and territories.
• With immigration and migration of people between provinces and territories, issues of vaccine interchangeability have arisen with specific concern regarding measles, mumps, rubella (MMR), varicella and meningococcal conjugate vaccines.
• For DTaP-IPV-Hib, the primary immunization series of three doses given in infancy should, whenever possible, be completed with a single combination product. However, on the basis of expert opinion, if the original vaccine is not known or not available, it is recommended that an alternative combination product be used to complete the primary immunization series. According to expert opinion and the limited data available to date, NACI recommends that the DTaP-IPV-Hib and DTaP IPV combination vaccine products currently approved for sale in Canada may be used interchangeably for the 18 month and 4-6 year booster, respectively.
• On the basis of expert opinion, the MMR products currently available in Canada may be used interchangeably if required.
• On the basis of expert opinion, the varicella products currently available in Canada may be used interchangeably if required

Development of evidence for interchangeability

Ideally, as new combination vaccines become available, there should be randomized controlled clinical trials evaluating their interchangeability with existing products. This has only been done in limited instances to date. Most of our knowledge regarding interchangeability has been gathered as a result of situations of vaccine shortages, immigration to areas where different vaccine products are available, and new product purchases with the negotiation of new contracts. Given the importance of this issue and the limited data available regarding the interchangeability of early childhood vaccines, every opportunity should be taken to encourage further research in this area.

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