The replication-deficient orthopoxvirus modified vaccinia virus Ankara (MVA) is a promising vaccine vector against various pathogens and has an excellent safety record. However, pre-existing vector-specific immunity is frequently suggested to be a drawback of MVA-based vaccines. To address this issue, mice were vaccinated with MVA-based influenza vaccines in the presence or absence of orthopoxvirus-specific immunity. Importantly, protective efficacy of an MVA-based influenza vaccine against a homologous challenge was not impaired in the presence of orthopoxvirus-specific pre-existing immunity. Nonetheless, orthopoxvirus-specific pre-existing immunity reduced the induction of antigen-specific antibodies under specific conditions and completely prevented induction of antigen-specific T cell responses by rMVA-based vaccination. Notably, antibodies induced by vaccinia virus vaccination, both in mice and humans, were not capable of neutralizing MVA. Thus, when using rMVA-based vaccines it is important to consider the main correlate of protection induced by the vaccine, the vaccine dose and the orthopoxvirus immune status of vaccine recipients.,
Scientific Reports
Erasmus MC: University Medical Center Rotterdam

Altenburg, A., Trierum, S., De Bruin, E. (Erwin), de Meulder, D., van de Sandt, C., van der Klis, F., … de Vries, R. (2018). Effects of pre-existing orthopoxvirus-specific immunity on the performance of Modified Vaccinia virus Ankara-based influenza vaccines. Scientific Reports, 8(1). doi:10.1038/s41598-018-24820-2