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Q&A: How do the COVID-19 vaccines work? Are they like the flu vaccine, will there be side effects?

Dr. Mark Casanova answered some of the most frequently asked questions WFAA has been getting about COVID-19 and the vaccine candidates.
Credit: AP
FILE - In this July 27, 2020, file photo, nurse Kathe Olmstead prepares a shot that is part of a possible COVID-19 vaccine, developed by the National Institutes of Health and Moderna Inc., in Binghamton, N.Y. Moderna Inc. says it will ask U.S. and European regulators to allow emergency use of its COVID-19 vaccine as new study results confirm the shots offer strong protection. (AP Photo/Hans Pennink, File)

Dr. Mark Casanova joined WFAA health reporter Sonia Azad live Wednesday to answer viewers' questions about the latest stage of the fight against the novel coronavirus. Casanova is the president of the Dallas County Medical Society and a member of the Texas Medical Association's COVID-19 Task Force.

The conversation particularly focused on the different vaccine candidates that are expected to soon be distributed to the public in phases.

Casanova answered a number of questions during the hour-long interview, but here are some of the biggest and most common questions that came up.

Watch the full interview:

Q: How will the different COVID-19 vaccines work in the body? Are they like the flu vaccine? What are the side effects?

Let's start with the flu vaccine, because I think it's a good, important starting point, and then we can talk about the Pfizer, Moderna vaccine and how those differ. And let's acknowledge that neither one of those vaccine platforms stand any probability or chance of giving you an active infection of the flu or COVID-19, respectively.

The Flu Vaccine

So, first of all, the annual flu vaccine. The way I describe it to my patients, it's as if you were taking the flu bug walking down the street, you take him, you strip off his overcoat, and that's what you mass produce in a vaccine.

So when you get the flu vaccine every year, what we've done is forecasted what the most likely overcoat colors for the season are. Is this going to be a blue, a beige and a short coat? Or a green, a yellow and a long coat? And that's what we're putting in that vaccine. So what you're getting is the outer coat stimulus of the annual flu vaccine, with the hope and anticipation that if we forecast it correctly and it turns out to be a short, blue coat, you're then protected.

And this is different every year because there's an evolution of the flu?

Exactly. Viruses undergo what we refer to as an antigenic drift, so ever-so slightly changing their fall colors, if you will, or their outer coat. 

What the COVID-19 virus did was it underwent an antigenic shift, which is a much more dramatic alteration, and that's what's made it so problematic. 

So, if an individual receives a flu vaccine, and that night or the next day they have some mild symptoms, typically pretty low-grade flu, what that tells us is that's actually your body responding to the vaccine, mounting an immune response so that when it recognizes that outer coat, that antigen from the actual flu bug, it's ready to mount a defense. Your immune system is revving up. We're going to get to this with the COVID-19 vaccines, because it does mount a more significant response. 

When we do get a viral illness, the virus itself is the culprit for triggering many of our immune responses. It can also directly affect many of our organs. It can cause pneumonia in the lungs. It can cause a condition called encephalitis, where the brain is actually inflamed and infected, and a whole myriad of other very serious issues. 

But your fever, those muscle aches, the generally feeling cruddy? That's actually your body. That's your body releasing cytokines, elevating the body temperature and doing other things to try to actually halt and/or kill off the virus itself. So it's a double-edged sword. Part of it is the bug itself, the virus itself, but another part of the side effects that occur are your body. 

Now, that's the story with the annual influenza or flu vaccine. 

The COVID-19 vaccines

Let's shift to at least the Pfizer and Moderna vaccines. I'll take those together because it's the same similar modality. 

Which is different from basically what we've been seeing with the flu vaccine or any other vaccine, it's a new vaccine technology?

Right, exactly. The principle has been around for a while, but I think this is one of the first widespread applied uses of taking that COVID virus that's "walking down the street" and stealing from it its sewing pattern, it's blueprint for the coat that it's going to wear. That's what we call the spiked protein. 

We've all become familiar with that sort of picture of COVID with those little spiky, crown-looking things that's on its surface. We call that the spike protein. That's what allows it to attach to our cells, insert its own messenger, its RNA and DNA, and then go to work replicating itself, taking over our own cells and turning them into its own factories, spitting out literally millions of copies of itself. And then having significant effect on the human body. 

So what the researchers have done is just take the blueprint, what we refer to as messenger RNA, that creates the spike protein, and that's what's actually in the Moderna and Pfizer vaccine that's injected into your shoulder. 

That messenger RNA works itself into your cells and does something similar to what many viruses do, which is ask your cells, ever so kindly, to begin to mass produce or replicate, not the virus, but that spike protein, that outer coat, or that outer coat marker, if you will. 

As your body does that, it begins to recognize this as a foreign entity and begins to mount a response to that, but what's unique about using messenger RNA is that response is much more robust. It actually incorporates more components of your immune system, including T-cell memory. So when you get that booster vaccine a few weeks later, you then get a more significant immune response. 

That significant immune response is going to come with flu-like symptoms. 

So to the question, are we going to get the flu? No, you're not going to get the flu. But are you going to feel crappy? Yes, you are. You're going to get a low-grade fever, you're going to get some muscle aches, that shoulder is going to be sore. But Tylenol or ibuprofen or Aleve are going to help mitigate those, and they tend to be relatively short-lived. It's about that night of that second vaccine dose, you'll wake up a bit tired and cruddy, but you'll certainly be able to go back to work the next day.

I listened to another interview with a doctor yesterday who kind of likened it to a colonoscopy where you know it's going to be kind of uncomfortable and unpleasant, but the protection that it offers sort of outweighs the other part of it.

I think that's a really good analogy. So much of life is built on expectations, right? If we have an expectation and understanding of what we're in for, I think it can really make things more tolerable, but also we just have a better understanding. 

There's transparency, there's candidness, you know that old adage when we're giving our 11-year-old their shots at the pediatrician's office, we really say, "This is only going to hurt a little bit." Well, it's probably only going to hurt a little bit for that annual flu vaccine. 

The COVID vaccine is going to cause a few more side effects. The irony is that these side effects are actually a huge positive. That's telling you your body is rearing up and ready to go if the coronavirus makes its way to you. So there's some irony built in to that. 

Q: Why do the vaccine candidates have to be stored at such low temperatures, and what if it's not kept cold enough?

The beauty of the messenger RNA vaccine is its effectiveness and its ability to mount a more robust immune response. 

The downside is that messenger RNA is a fragile substance, if you will. It's not an inert substance like a protein that we put in the annual flu vaccine that really can live, or not degrade or breakdown, at room temperature. The flu vaccine is a very stable vaccine that doesn't require fancy storage techniques. 

Messenger RNA is sort of a delicate molecule and does need to be kept at very cold temperatures, and for the Pfizer vaccine at super-cold temperatures. They're slightly different for each, but the data does suggest that when taking that out of a deep freeze, you have a certain window that the vaccine will be stable and effective when delivered to an individual.

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Q: Is the AstraZeneca vaccine less effective than the others?

That's a great question. And let's talk about effectiveness. If the Pfizer vaccine and Moderna, when deployed on a nationwide, if not worldwide basis, do hold to this around 90% effective rate, that's an amazing accomplishment. That's knocking vaccine effectiveness out of the ballpark. 

We are generally content if a vaccine has somewhere in the range of 50 to 60% effectiveness. Some annual flu vaccines will have effectiveness in the range of 30%, and part of that is that forecasting and getting the design right for the year for that particular flu vaccine. So in the initial data, if these vaccines carry a 50 to 60% effectiveness or a little bit higher, in the grand scheme of vaccines, that's still considered to be a positive. 

I also think some of these vaccines may end up ultimately having niche roles or niche distributions. We talked about the struggles with the Pfizer vaccine having super cold temperatures, the Moderna at least having really cold temperatures, and the two-shot series and the logistics behind that. 

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It's possible that into early next year and into the spring when we have other vaccine candidates come down the pipe and we can get a critical mass of the public vaccinated with one vaccine or another, that the effectiveness difference of 90% to 60% will work itself out in the wash and we'll still have, globally, an effective protection of our community. What we refer to as true herd immunity, not the altered definition of herd immunity that we've been hearing over the last several months. 

When you hear that phrase, it applies to vaccination of a population to effect community protection, acknowledging that some of us may not get the vaccine for whatever reason, or that some of us who get the vaccine are getting a lower equivalency vaccine. But at the end of the day, if enough of us are protected and the virus is bouncing around and can't find a host, it eventually dies off.

Q: When a vaccine is approved, am I going to get a choice between a vaccine? How will immunization be tracked?   

That's a really good question, and the answer is going to be somewhat forecasting in prediction of the future. 

By the time we have an adequate supply of vaccine for the masses that one of the viewers that is not listed in one of those high-priority groups— frontline workers, hospital workers, loved ones who live in nursing homes— by the time they are going to their local Walgreens or CVS, we're going to be further down the road. 

It will be extremely important for you to know which vaccine you're getting. If it is a vaccine that requires a second injection at time point X, you'll need to make sure that you get that same vaccine.

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Texas and many states already use vaccine tracking databases called Immtrac. We need to ensure that "Bill Jones" who got the Pfizer vaccine on Jan. 30 gets that Pfizer vaccine again on Feb. 21 or three weeks later, so that's going to be very important.

Those systems aren't really in place yet, and I think part of the fear and worry that comes in with humans is no one's told us how this is all going to work.

Right. And as one can imagine, there's a lot of work happening behind the scenes. I'm being optimistic; I'll be candid and transparent that I am hopeful and very optimistic that this will work itself out. 

And for better or worse, it's going to be the timing of the rollout and the supply of the vaccine that's going to give us the opportunity to work this out. The first wave of the vaccine is going to go to very controlled settings, like employees in hospitals or nursing homes.

So we're going to have that timeframe to get the ball rolling while at the same time ensuring that physician's offices, family medicine offices and your local CVS or Walmart, and maybe a community center in some areas, can create that infrastructure and hone it up to the ability to do this both in an expedient fashion, but a safe fashion as well. 

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Q: Can you clarify how the vaccine works since the virus can re-infect the body multiple times? How long does immunity last?

So, for the Pfizer and Moderna vaccines, the incorporation of other components of the immune system, of T-cell memory and whatnot, is important. When we're talking about the immune system, we're talking about a series of different families of white blood cells, but also all the different things that these white blood cells can do. Many vaccines will provide the protection of just one family. These new vaccines are actually bringing in multiple components of your immune system to bear response. 

Having said that, we won't know how long that immunity lasts until we've been in it for a spell. So the vaccine studies are not going to allow us to have a predictable timeframe of 'Yes, this protects you for X amount of time.'

This is probably going to be well in to the end of 2021 into 2022 as we do an analysis to determine what's the staying power of these vaccines and if they will ultimately require boosters.

Q: If you've had COVID-19, do you need to get the vaccine?

Great question. We do believe it would be advisable to get the vaccine. 

I think if you have COVID right now and, theoretically the vaccines are coming to bear for the general public in the spring, maybe you're not at the front of the line. Maybe you say 'Hey, others who don't have a vaccine, please go to the front of the line. I had it recently, I'm being very careful.' 

The question gets to the issue of can you be re-infected with COVID-19? The answer is yes, but the question of what's the average timeframe is up for continued exploration and we're still trying to learn it. 

I think ultimately, even if you've had it, it's probably going to be a good idea to get it. 

Edited by WFAA digital producer Jennifer Prohov for length and clarity.