In a little over a year since it was first reported in Brazil, Zika virus has gone from a little-known member of the flavivirus genus to one of the most reported on viruses in the world. Open any newspaper and you’ll find an update on the ongoing epidemic. For the most part the news is dire – counties reporting their first Zika cases or the CDC releasing new numbers on Zika infections during pregnancy – but last week the world got a respite.
A paper published in the journal Nature reported on the development of not one, but two different vaccines against Zika – one a subunit vaccine, the other an inactivated vaccine – and both successfully protect mice against Zika infection after a single dose.
A subunit vaccine is a type of vaccine where only part of the virus is used to generate immunity – in this case, Zika’s envelope protein forms the bulk of the vaccine. In an inactivated vaccine the entire virus is used, but it is inactivated or “killed” by chemicals or heat, which renders the “killed” virus harmless to humans but still capable of generating protective immunity.
As the world became aware of the scope of the Zika outbreak, calls for scientific collaboration rang out. According to Justin Iampietro, a Harvard graduate student and co-author on the Nature paper, both vaccines are the result of such a collaborative effort, involving researchers from the University of São Paulo (USP) in Brazil, Harvard Medical School and the Walter Reed Army Institute.
One benefit of collaboration is speed. Work on the subunit vaccine began in February and the results were published in late June: five months from start to publication. Furthermore, pharmaceutical company Sanofi-Pasteur has teamed up with the Walter Reed Army Institute to begin testing the inactivated Zika virus vaccine in humans in October.
If you were hoping this meant a vaccine would be available in time for the Rio Olympics in August, you’re in for disappointment. Vaccine trials require multiple phases, each testing for a separate aspect of the vaccine and requiring increasingly larger numbers of participants. It can take years to get from a small Phase 1 trial looking at vaccine safety to a Phase 3 trial, which explores vaccine effectiveness and includes thousands of individuals. While a Zika vaccine may be two to three years away, the ability to successfully protect mice against Zika infection is an important step in the search for a safe and effective human vaccine against Zika.
Special thanks to Justin Iampietro a Harvard graduate student in the virology program, for his time and insider commentary on both of the Zika vaccines.
Larocca et al. Vaccine protection against Zika virus from Brazil ( Nature ) – open access