It sure would be nice if we had a vaccine for COVID-19, wouldn't it? In movies about pandemics, there's usually some big dramatic scene where they find a person who survived the disease. Then POOF, the next thing you know the whole problem is solved. Unfortunately, finding safe, effective vaccines is not that easy.
Your body has a defense system that is called the immune system. It mostly works on identifying shapes. All of your own cells have a sort of ID badge, which is a shape on the outside of all your cells. The immune system checks ID's all of the time. When they find something that doesn't belong, they launch an attack. Some cells eat the invaders. Others make antibodies that stick to the invaders, stopping them and marking them for other cells to remove. But it can take the immune system some time to notice the invaders and build up a big enough response to stop every invader.
Here's how a vaccine works, it's sort of like a WANTED poster. Once your immune system has "seen" a particular shape, it leaves behind memory cells that are sort of like wanted posters so that if the immune system ever sees it again, it makes a big response right away. This usually stops the invaders.
A vaccine uses either a piece of a virus or a virus that is damaged to alert your body's immune system. The problem is that viruses have been evolving for a few billion years and the ones that survived have been the ones that avoided being found by immune systems. So finding something on a virus that a person's immune system will recognize is not easy. Researchers also need to make sure the vaccine is safe. This all takes time.
The good news is that safe, effective vaccines are possible. Hundreds of millions of people have died of smallpox in the past. Now no one does, thanks to vaccines. We have nearly gotten rid of some other diseases, but because some people will not get vaccinated, those diseases can come back. That happened with measles. There is a safe, effective vaccine, but some people wouldn't take it, so it spread again.
I have an assignment for you. Call your oldest relative (or family friend) and ask them what they remember about diseases like polio and mumps from their childhoods.
Thanks for asking,
A vaccine works by activating an animal's immune system against a possible disease before that danger arrives, thereby ensuring that the immune system is prepared to fight the disease if and when it does arrive. As a result, in order to create a vaccine that works against a disease, we have to understand how the immune system responds to it in the first place. This requires study of the disease itself, and if the disease is difficult to study because it only produces symptoms in some people, or is too deadly, then that can make it difficult to learn what is necessary to create the vaccine.
You're probably asking about COVID-19. COVID-19 does not produce symptoms in a significant fraction of the people whom it infects, so it is difficult to know whether or not they have it. In others, it may be deadly too soon.
We don't want bunches of people to die because we developed a dangerous vaccine - or a vaccine that seemed to work but didn't really work, so lots of people thought they were safe, but they got the disease.
That's part of the answer - it's hard to know that a vaccine works well and that it's safe, unless you spend a long time testing it and test it on a lot of people, after you've tested it on a lot of animals.
I just heard a webinar about face masks, and it said all our vaccines took between 5 and 11 years to develop! But they hope to get a vaccine for Covid-19 in about 18 months.
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