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Johanna Swanson Product Manager at GlobalData comments: “Repeated administration of adenovirus-vectored vaccines can cause the generation of neutralizing antibodies to attack the adenovirus vector present in the vaccine and reduce the effectiveness of the vaccine or any vaccine based on a similar vector. This could be a problem for the adenovirus-vectored vaccines by companies such as AstraZeneca CanSino ImmunityBio J&J Altimmune Stabilitech BioPharma and Vaxart - though some of the companies are working on mitigating this issue.”
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ImmunityBio is using a version of the Ad5 vectors that has additional gene deletions which could reduce the immune response to the vector. Others such as Vaxart Altimmune and Stabilitech BioPharma are using alternate administration such as nasal spray and pills instead of injection to reduce the immune response to the Ad5 vector.
J&J is using the Ad26-based vector vaccine to avoid the general neutralizing antibodies by previous exposure to common adenovirus and AstraZeneca’s vaccine uses an adenovirus that normally infects chimpanzees but not humans. Repeat administrations could still be an issue if individuals develop antibodies to the vector after first or second administration.
Swanson adds: “These vaccines might have to be modified to use a different vector for the second injection or we may have to wait for alternative booster vaccines without vectors in them to be used after the second year of vaccination.”
