Why vaccine run is slower than the epidemic spread of virus?


Ebola under SEM (Courtesy: CDC)

Are we aware? What is happening? Where are the vaccines that proved to be successful? Why Ebola vaccines are still under trial? Why are there success stories been proposed in research papers? I am sure that these questions are must and most obvious. There are several reasons why a laboratory proposed vaccine needs long time to launch in market. Here in this small note brining you forward about why vaccines are slower than the epidemic run of virus.

While we take two names those come first are Zika and Ebola. Looking at Zika three vaccine candidates have proved to be successful in monkeys and another has reached under human trials. Unfortunately the run of Zika is much higher. It has already reached 66countries after Brazilian epidemic. On the other hand looking towards Ebola, two vaccines have reached its final trial. But Ebola had been reported to halt its spread since the last update on 10th of June with 28,616 cases and 11,310 deaths. (Read Ebola 2016 update on Biomysteries). So hopes are high but vaccine run is too slow and may be the Zika virus vaccines may take a year to reach the market.

So here are some reasons why vaccines are backlogging

  1. Before Epidemics

When disease starts to spread and often it takes late to understand what it is that is spreading high. So taking example of Zika which was known to spread in Brazil early August 2015, World Health Organization (WHO) reported its alarm in February 2016. In between Zika already has reached to be pandemic. For Ebola too, it took the same time to be understood what it is that spreading. Even investigators get affected with Ebola.

  1. Shifting strains

There are different strains every time. Common example would be Influenza which have multiple strains based on the protein coat Hemagglutinin (H) and Neuraminidase (N). So it is named on the type of strains like H1N1, H2N3, H1N4, etc. Similarly for Zika there are two strains African and Asian. The recent hit is considered to be similar to Asian strain. One of the scientific reason is low processivity of Viral DNA proofreads. So it may shift in between the strain. More it shifts slower would be the run for vaccine.

  1. Risky business for companies and lack of funds

It is not about the virus but about the vaccines. Big pharmaceutical companies can invest only for research and few come forward while there is an urgent need of vaccines. WHO also needs enough support of various companies to eradicate the Viral attack. The negative side lies when vaccines does not overcome all the clinical trials and make them push towards losses. So it is a big job for pharma companies to think before they invest. Whereas, WHO also lacks enough funding and it needs support so that all from the world can collaborate.

  1. Animal models

Once Scientists make a potential vaccine it has to be tested on rodents like rat or mice specifically. But sometimes it is not enough available to undergo testing. Also, it is not always that vaccines that worked on mice will work similarly on humans. The virus also may not affect rodent’s similar way as it does on humans. Although mice holds most genetic similarity with us but it is not same as humans.

  1. Reaching Human trials

It is the ultimate goal for any researchers to push the vaccine to human trials. It is not always to take lightly but there are many vaccines that made it to human trials. Unfortunately the bad news is companies struggle to find enough volunteers to continue the trials.


It is just a brief story about the hurdles that most vaccines need to face. The morale of the story is although the epidemic spread runs like rabbit but the race is finally for vaccines although it runs like turtle. It needs enough support to build the bridge between the clinical trials. Scientists, organizations and companies are equally struggling to halt the spread of Zika with successful vaccine. Hope the final news hits soon.


About Saumyadip

Science Communicator and Biologist. Keep interests in host-pathogen interaction research. Specifically bacterial infection mechanism, host infection evasion and immune susceptibility of host. PhD student at Academia Sinica Molecular and Cell Biology, Taiwan
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