Zika vaccine: When ?

When can we expect the first Zika vaccine on the market ?

Zika vaccineZika virus has spread rapidly in South and Central America in 2015 to 2016 and outbreaks have been detected in Southern parts of the US like Florida during the summer 2016. This virus is carried by the mosquito Aedes aegyptii and is dangerous for pregnant women because it is associated with babies microcephaly. In addition, it has been shown that the Zika virus is the cause of some rare neurological diseases in adults like Guillain-Barre syndrome in which people experience muscle weakness and paralysis.

So far there is neither therapeutic products to cure the diseases nor a Zika vaccine to prevent the disease. The only ways to escape the virus is to avoid bites from mosquitoes and the list of the best repellent products, mosquito traps and bed nets are reviewed on this site. The WHO has urged Big Pharma companies to develop a Zika virus vaccine but funding  of this research has become a hot topic: the Big Pharma don’t see quick return on investment since there is no proof that the disease will spread again in the near future and politicians are not willing to spend millions of dollars with no cure available before years.

The companies have proposed different strategies for Zika vaccine development. It’s very technical so I won’t explain them in details. They talk about live attenuated vaccines,  inactivated vaccines, DNA vaccines, etc. The big issue to develop the vaccine will be the design of the clinical trial. For example, the first question to address will be which target population to be enrolled in the study ? Second, is how to measure the efficacy of the candidate vaccine ? Third, how to enrol people if Zika does not reappear in the South American countries ? To date, two companies have proposed their support and will collaborate with the US Health Agencies. The first early clinical trial (called Phase I trials) begin recently and the first trials with more subjects to evaluate efficacy and safety of the candidate vaccine (called Phase II trials) are planned early 2017 (Abbasi, JAMA 2016). The first preliminary data could be available as of 2018 but, overall, it will take 3 to 5 years to enroll subjects, perform the analyses (participants will be followed for at least two years) and market the products. Regulators across the world are also in discussion how to accelerate the studies and the evaluation of the data prior to licensure. For example, if there is no disease outbreaks anymore in South America, they suggest to vaccinate infected primates and compare their immune responses with humans or to inject the virus in humans and then evaluate their immune response and safety of the vaccine in well-controlled studies in hospitals. In conclusion, even with different competing vaccines and development strategies, we can’t expect the first Zika vaccine on the market before 2020. Hoping that no Zika outbreaks will emerge in the meantime !

 

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