Some vaccination schedules require a first dose followed by second or third booster doses. Mixing vaccines (vaccine interchangeability) is when a person receives an initial dose of one vaccine and a booster dose or doses of another vaccine made by a different manufacturer. The different vaccines used may work in different ways to activate the body’s immune system.
How might vaccines against the same disease be different?
There are several ways in which vaccines designed to help the immune system develop protection against the same disease can be considered different. For example:
- Vaccines may use different methods to prime the body’s immune system to fight off an infection. These methods could include introducing the body to an inactivated or weakened form of a virus or using carriers to provide the body with genetic information to prompt an immune response.
- The steps within the production of similar vaccines, that have the same mode of action, may vary between manufacturers. This may mean that vaccines could contain different concentrations of their active substance, different preservatives, or different stabilisers. They may have distinct storage requirements, for example needing to be kept at a certain temperature.
What are potential benefits of interchangeability?
A key area of interest is whether it may be beneficial to use different types of vaccine in the same individual to improve their level of protection against a disease.
Additionally, the use of vaccines interchangeably may:
- Promote flexibility in relation to the dose and frequency needed to provide protection.
- Give more options for administration, for instance in situations where a product used earlier in a vaccination series is no longer available or, at the time a later dose is required, details of the earlier type of vaccine used is not readily accessible.
- Allow manufacturing to proceed more quickly, for example by reducing competition for raw materials.
- Address logistical challenges, for example providing flexibility in terms of transportation and storage.
- Increase their overall availability.
Ultimately, this may help to achieve a high level of protection against disease across populations to prevent transmission, hospitalisation, and severe illness.
Are vaccines already used interchangeably?
Vaccines may be used interchangeably for some childhood vaccinations. Studies have shown that immunogenicity can be sustained with vaccines made by different manufacturers used in the same individual to complete a vaccination programme for certain diseases.1 However, currently, advice is generally that it is preferential to use subsequent doses in a vaccination series from the same manufacturer where possible.2
What research is being conducted around interchangeability?
Vaccine interchangeability continues to be a key area of research. Studies include looking at the effect vaccines have on the immune system over time and the benefit or risk of different vaccine combinations. These types of studies will help to inform future vaccine development and vaccination schedules.
1. Feldman, Sandor MD. Interchangeability of vaccines, The Pediatric Infectious Disease Journal: November 2001 - Volume 20 - Issue 11 - p S23-S29. Last accessed: July 2021.
2. American Academy of Pediatrics Red Book 2021-2024 Report of the Committee on Infectious Diseases. Interchangeability of Vaccine Products. Available at: https://redbook.solutions.aap.org/chapter.aspx?sectionid=247316421&bookid=2591 Last accessed: July 2021