MVA-based influenza virus H7 vaccine protects against H7N9 infection

NIAID CEIRS | Research Publication Commentary

Kreijtz JH et al. A single immunization with an MVA-based influenza virus H7 vaccine affords protection in the H7N9 pneumonia ferret model. J Infect Dis. 2014 Sep 22.

Effective influenza vaccination strategies will be key to controlling the spread of a pandemic. However, a pandemic vaccine cannot be manufactured in advance as the causative virus cannot be predicted. Therefore, developing and stockpiling potential pre-pandemic influenza vaccines has become an attractive alternative to preemptively mitigate a future pandemic. Pre-pandemic vaccines are directed towards existing strains that appear to have pandemic potential, such as the currently circulating H7N9 avian influenza strain. To date, sustained human-to-human transmission has not been documented for H7N9 infections but were the virus to gain this ability, it could spread in the human population and pose a public health concern.

In this paper, Kreijtz et al. used recombinant DNA technology to develop a viral vector vaccine (MVA-H7-Sh2). This vaccine is based on modified Vaccinia Virus (Ankara strain, MVA) expressing the hemagglutinin (HA) glycoprotein from A/Shanghai/2/2013 (H7N9). Ferrets immunized with the MVA-H7-Sh2 vaccine developed protective antibody titers against the H7N9 influenza virus. Following virus challenge, immunized ferrets were also protected from severe disease symptoms associated with H7N9 virus infections. The efficacy of this vaccine was found to be dose-dependent; ferrets that were immunized at a lower dose had a lower immune response than ferrets immunized at a higher dose.

While the MVA-H7-Sh2 vaccine appears to protect ferrets against H7N9 influenza virus infection, more research is needed to expand the safety and efficacy track record of MVA-based vaccines in humans. Moreover, a comprehensive vaccine repository that collates information about vaccine efficacy would be a valuable resource to inform decisions as to which pre-pandemic vaccines to develop and stockpile.