Flu vaccine efficacy

So let's say you're walking down the street and you see this person, this green, sickly person. And this person is coughing and sneezing, and you feel really bad for them right? Because they look awful. They just must feel awful as well. And the thought that goes through your mind is, how do you avoid getting sick as well? Because of course, you don't want to feel this way either, right? And so you want to think about all the things that you can do to make sure you don't get sick from this person. And so what are some of those things that you might be able to do to try to avoid getting sick? Well let's think through it. How are you interacting with your environment? What's the only real way in which you interact? Well, it's when you touch things, right? You usually have your feet and your body covered up, but your hands are always exposed, and they're always touching things. And then you usually turn around and touch your mouth, your eyes, or your face. So two real quick things that you can do to try to prevent getting sick are simply making sure that you wash your hands. And that's why you always hear that message, wash your hands after going to the bathroom, before you eat. And that's the reason why. And the other key message is, don't touch your face. Right? You want to make sure you avoid your mouth, your eyes, your nose. Because that's where the viruses get into your body. So don't touch your face. So these are two really good ideas, right? But what are some others? What else can you do? Well, you can try-- and this isn't always possible-- you can try to avoid the person altogether. You could try to just move away, right? You could say, well, let's make some distance over here. So you're further away from this person. And that's another possible strategy. And like I said, it doesn't always work. But when you can avoid someone, that's always a good idea. So avoid sick people. And finally-- and this one is going to be the main point of this video-- is you can actually get vaccinated. You can get a vaccine that will actually prevent you from getting ill. So flu vaccine is something that a lot of people have strong feelings about. And the first thing I want to point out is, on this list of prevention it's probably the most important. It's probably the most effective way of preventing getting sick from the flu. So certainly think about it. But if you're going to think about it, and you want to think critically about doing something like this, you want to make sure it's a good idea, right? Do we really have any evidence that it really does help? Or is it the opposite? Does the flu vaccine actually make you more sick? Does It gives you the flu? So let's talk about that. Let's think through how the vaccine works and what we know about it. So there's some research that's been done on flu vaccine. I'm going to present you with what we've learned so far. So a group out of University of Michigan actually came along and they said, well, let's figure out the answer to whether vaccine is a good idea. And let's actually take-- let's start over here on the left side-- let's take an injection and fill it with salt water. So this is regular old salt water, or something very similar to it. And it has no real effect at all. In fact, sometimes people call this placebo. And I'll actually write that over here-- placebo. So that's one side. And on the other side, let's actually come up with a vaccine. And this vaccine I'm going to draw out, it looks basically the same. It's actually also an injection. And this injection is full of dead virus. So they literally take live virus-- remember live virus has kind of an envelope, and it has RNA on the inside. I'm going to sketch that out. And what they do is they actually have different ways of killing it. They literally just destroy this thing. And just like human beings, you know, if you're killed, you cannot come back to life. And a virus is the same way. Once a virus is dead, it is dead forever. And so this dead virus is lying here on its side, completely and utterly dead, right? And this dead virus, then they take it and they put it into the vaccine. So this is what is in the vaccine. This is our flu vaccine. Let me label it over here. Flu vaccine. So two groups of people then, are going to get two different types of injections. And they actually had hundreds and hundreds of people involved in this study, but I'm just going to show you a representative slice. So let's say this is 100 people over here. And that's a grid, so each square represents one person. And there is 100 people over here. And these people, they don't know which vaccine they're going to get. They don't know if they're going to get the salt water or the flu vaccine. They're what we call blinded in this study. And I should also tell you that these people are very healthy, and they are young adults. So they're between 18 and 49 years old. They're healthy. And the two groups are fairly similar in terms of the number of men and women in each group and their age breakdowns in the two sides. They're fairly similar. So these two groups get the salt water or the flu, and they don't know which is which. And they're told over the course of six months, over the course of the flu season, to keep track of illnesses. And if they get flu, I'm going to sketch them out in red. What they actually did is they said, hey, if you get the flu, let us know and we'll confirm it. We'll actually do a lab test to make sure that it really is the flu and that it's not just some other illness that you think you have. So they actually took all these people that said they had the flu-- and I'm only going to draw them in red if they were confirmed by PCR. That was the lab technique they used. So these were called PCR confirmed. So that's laboratory-confirmed illness with flu. So these are people with PCR-confirmed illness. And there were, you can count them out. Out of 100 people in the first group, in the salt water group, we had a total of 10 individuals. So about 10% of these folks were ill with the flu over the flu season. And on the flu vaccine side, we also had some people sick with the flu. So that's actually the first thing you should know is that the flu vaccine does not prevent you 100% from getting the flu. But look at how many people I shaded in. In the placebo side I said there were 10 out of 100 people that got sick. And on the flu vaccine side only about 3 out of 100 people got sick. And both-- actually I should put arrows on both sides-- both were PCR confirmed. So what does this mean? How do we take this and make some sense out of it? Well, there's a term called "vaccine efficacy." And what it kind of refers to is, how good is the vaccine at preventing you from getting sick? So this is the term "vaccine efficacy," and sometimes you might even see the term "VE." Sometimes people use "VE" for vaccine efficacy. And the way you calculate it, you say VE equals the proportion of people that got sick with the salt water-- so that was 10 out of 100-- minus the proportion that got sick with the flu vaccine. So minus 3 out of 100. And you divide by the group that did not get vaccine. And so you can take this and you could simplify it. You could say, well, this is basically 7 over 100 divided by 10 over 100. And you could make it even simpler by canceling the 100s out, and you say, well, this is just 7/10. And to make a percent of it, you multiply 7/10 by 100%. So if I was to describe the VE, or the vaccine efficacy, based on this study, I would say, well, flu has a 70% vaccine efficacy. So you see how we got that number. It's fairly simple, right? Just comparing the two groups to each other. And there have been many studies on flu. And the CDC actually took all this data and they said, well, in general, the VE, or the vaccine efficacy, for the flu vaccine is usually between 60 and 70%. That's kind of the number that they usually quote for this vaccine. So let's now take that number, 60 to 70% VE-- I'm going to write that down here, so we don't lose track of what that is-- and let's take that back up here to our little example. We said that there are a few ways to try to prevent the flu. And if I imagine now that there's a force field around me-- let's say there's a little purple force field around me-- and this force field protects me from germs. I'm going to show germs coming in and bouncing off my force field. Well, this would be really accurate if I was describing 100% vaccine efficacy. Meaning if I get the vaccine, I'm completely unable to get sick. But we know that's not true. We know that it's actually closer to 60 to 70%. So for 60 to 70%, let me show you what you can change this picture to look like. Instead of making it completely impenetrable, you can just draw a few holes in it. So a few holes there, maybe be a hole there, and maybe be a hole down here. So now you can show a few of the germs breaking through and getting in, right? Maybe getting in over here. But many of them actually still bounce off. And so you're still protected by a lot of the germs, but some of them can still get you sick. So probably the best way to avoid getting sick then, is to get your vaccine, but still make sure you wash your hands, don't touch your face, and avoid sick people.