A couple of days back, the 
There is no one specific answer to this question. The difficulties in developing a safe vaccine requires a lot of in depth understanding of the Human Immune system and how it responds. That's an extremely complicated discussion, which I will no be going into detail in this post. I have been extremely stressed out recently and i find it really difficult to post regularly to my blog, let alone write up an extremely complex post on immunology. If time allows, maybe in a couple of months, (hopefully after mid July, *fingers crossed) I'll try to discuss the human immune response in detail. Maybe even a series, who knows!
But for now, just a very very basic understanding of how vaccines work in Non-scientific terms mostly for a wider range of readers to understand.
Vaccines can be against both viruses and bacteria, but I'll use the term virus only throughout this post for simplicity.
Whaaat! You crazy Doc?
No. I'm not.
Vaccines are made to prepare your body to kill the virus. Vaccines don't do the killing for you. Vaccines are given so that the body is ready to kill the virus once you are infected.
To understand this, we need to know what's in a vaccine. A vaccine, in general can be one of three things.
So what happens when you're given a vaccine is that your body encounters certain identifying structures aka the Antigens of the virus without the risk of having the disease. You are teaching your body's immune system some characteristic structures of the virus. The body's immune system then prepares itself to fight or respond with it's guns and bazookas against that specific structure, to attack that structure ASAP if you are infected. Remember, the body does not recognize a virus or bacteria as a whole. It only recognizes specific structures that are different and characteristic to different viruses and bacteria.
So when you get infected by a virus that has an Antigen on it that your body has Learned about previously, either by vaccination or a previous infection, the body responds really fast! When you get infected the first time, the body's response is quite slow, giving the virus to cause the disease. But from subsequent times, when the body encounters an antigen it has encountered before, it is already ready to go guns blazing! The response is super fast and the virus is killed before it even has a chance to cause the disease.
Now what's happening with this SarsCov-2, and most viruses of the coronavirus family such as rhinovirus (the one that causes common cold) is that they are changing these structures too frequently via mutation.
So the body may get prepared for one structure, but when you actually get infected the next year, the structure your body learned the previous year isn't there and there’s a new structure which the body doesn't recognize and can't act rapidly. The response will be slow and the virus has the chance to cause disease.
This is why once you get infected by chicken pox, you never get infected again. Because the virus isn't changing it's structure and if you are infected again the body acts rapidly killing the virus before you get symptoms.
The same reason why you get common cold every year. The Rhinoviruses are sly. They are changing the antigens too often and can keep re-infecting us.
Now is this the only reason we can't develop a vaccine against SarsCov-2? Probably not. Is this even a reason? Not sure, too little data to come to a conclusion. This virus is extremely new and we don't know a lot yet.
A great question came up from 
One simple question. Is it true that Corona is also similar to Chicken pox. If someone gets it once and recovers, they don't get it again?
We don’t have enough information on that. But so far I have heard of only one case in china where the person was re infected. It might just have been a case of discharge before full cure. So still too early to tell. Until we have more info, we should assume the answer is yes and stay cautious.
Well that was a very basic starter pack knowledge on vaccines! Join the Neoxian city Discord Server and get in on the ride where we talk about everything starting from cryptocurrencies to the field of medicine to recipes from 
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That's all from me for now!
Until Next Time!
Peace!
