Your biggest Pfizer/BioNTech and Moderna Covid-19 vaccine questions, answered
December 16, 2020
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by admin


It’s been a busy week in vaccine news: The FDA authorized the first Covid-19 vaccine in the US on December 11, and the vaccination campaign is underway. The first US health workers received the Pfizer/BioNTech Covid-19 vaccine on December 14.

With all of the news around coronavirus vaccines, of course, comes a lot of questions. Vox science reporter Umair Irfan joined Today, Explained in a live conversation with host Sean Rameswaram to answer some of the biggest questions from our podcast listeners. (A transcript of their conversation, lightly edited for length and clarity, follows below.)

The live podcast event also featured a conversation with Dr. Anthony Fauci. The nation’s leading infectious disease scientist spoke about everything from his personal reflections on the past year to what it will take to get to “true herd immunity.”

The Fauci segment of this live podcast event will air next week as part of the Today, Explained upcoming podcast series “You, Me, and Covid-19,” which looks back on how the coronavirus has fundamentally reshaped our world. Through reporting, listener reflections, and interviews, the team will examine how Covid-19 changed our relationships with one another and with the places we live, upended our livelihoods, and redefined what we think of as “normal.”

The first episode of the series drops on Monday, December 21, and continues throughout the week. Subscribe to Today, Explained wherever you listen to podcasts — including Apple Podcasts, Google Podcasts, and Spotify — so you don’t miss an episode.


How is the Pfizer/BioNTech Covid-19 vaccine different from existing vaccines for other diseases? And how does the vaccine work?

The one thing to highlight is the unprecedented speed at which we have developed this. Vaccine development is something that typically takes decades. The fastest vaccine ever developed was the mumps vaccine that took four years. This was a disease we only discovered last year around this time.

And now about a year later, we already have a vaccine that’s starting to be distributed. So this is something that’s unprecedented in terms of science. And the other big thing to highlight is that this is also using a completely new technology. Both the Pfizer/BioNTech vaccine and the Moderna vaccines are using an approach [with] the RNA-based genetic material. This is something that we’ve never tried on large scales in humans before.

So the old-fashioned way of doing viruses or vaccines was you would take the virus — weaken it, kill it, or snip off a piece of it — and inject it into the body. And then your immune system would read that and develop a response. They would use it as sort of a punching bag to essentially prepare for when the virus actually invades.

What these new generations of vaccines are doing is you don’t need the virus at all. In fact, all you do is you start with the genetic material. That is the information used to code for how to make the virus. And you don’t even need to know how to make the whole virus. You only need to know how to make a piece of it, like the spike proteins.

So with the coronavirus, the spike proteins are really important because that’s what they use to break into cells. They’re kind of like lock picks. And so what [companies] like Moderna and Pfizer have done is they took the instructions in RNA and they basically inject those into the human body, into muscles, and then your own cells will read those instructions and then manufacture their own copies of those specific spike proteins. Then, your immune system will use that as target practice.

And so this is, again, something that we’ve never done before, but it’s extremely fast. The first mRNA vaccines were developed within days of the genetic sequence of the coronavirus being released publicly. And then within two months, they were tested in the first humans.

Who qualifies for getting the Covid-19 vaccine now? And when might everyone else actually be able to get it?

Let’s start backwards and work towards where we are now. Ultimately, we want everybody to be vaccinated against this as much as possible because this is a disease that can infect just about everybody. So that’s the ultimate goal post, trying to get as close to saturation.

But, of course, we can’t do that right away. So the Centers for Disease Control convened an advisory committee, and they looked at where would these vaccines be most effective, not just in terms of preventing deaths but also in terms of preventing spread.

If we can inoculate [people who are most likely to spread the virus to other people], we can control transmission. They found out that those people are likely going to be health workers. So the first priority on the list are logically going to be health workers, but also people who live in long-term care facilities, older adults, and particularly the people that work around them.

The idea is that these people can act as sort of firebreaks against this inferno of a pandemic. The problem, though, is when you add up those people just in those high-risk groups, that’s 24 million people. And we’re not going to have 24 million doses right away. The Operation Warp Speed estimates that will have just about 20 million Americans inoculated by the end of December. And that’s if everything goes perfectly well, which means that there will still be some people that will have to wait.

So it really is going to vary from state to state and even from region to region. Different states and different hospitals have their own guidelines. Some of them are developing an algorithm which sorts out who is at highest risk. Some of them are awarding vaccines based on a lottery system. Your odds of getting a vaccine — or when you will get it — really depend on your city, your state, how many vaccines they received, and how effectively they’re distributing them.

Can people get Covid-19 between the two doses?

Yes. Both the Moderna vaccine and the Pfizer/BioNTech vaccine are two-dose vaccines administered about several weeks apart.

Last week, before Pfizer/BioNTech received their emergency use authorization from the FDA, they released some of their data showing their trial pool. The data showed that they had about 160 some people who got infected with Covid-19 in the placebo group and about nine people that got infected in the group that got the vaccine.

But if you look at when they got infected, most of those nine people were infected just a few days after they received the first dose of the vaccine. So between the first and second dose, building up an immune response is something that can take several days up to a couple of weeks. It’s likely that they were still vulnerable in that window where they were infected. Basically, the vaccine hadn’t kicked in yet, and so they were able to get infected and get sick in that specific time frame.

Can people get Covid-19 after receiving both doses of the vaccine?

Yes. There were a couple of people that, I think, were reported to have received the vaccine to have come down with Covid-19 after getting the second dose. Those will have to be investigated further; that’s why we don’t say this vaccine is 100 percent effective. Ninety-five percent effective is still very high. But it also means that not every single person who gets a vaccine is ultimately going to have protection, which means we still have to take some precautions even after getting vaccinated.

What do we know about long-term health effects of the Covid-19 vaccine?

We’re still learning about them. Generally, we would expect most complications with vaccines to happen shortly after you get the vaccine. Even though we’re only getting the results of the phase 3 clinical trials in the past few weeks, you know, we’ve had phase 1 and phase 2 trial results for several months. So, we know for the most part that most people don’t really have a severe reaction to this.

The main side effects after getting the vaccine are going to be muscle pain, weakness, some redness and soreness, and a mild fever. Those are the most common complaints. We don’t really have good long-term safety data just simply for the fact that this virus and this vaccine [have] not been around very long. In order to get the emergency use authorization, Pfizer had to provide two months of safety data. But they’ve also committed to following their candidates in their phase 3 clinical trial for up to two years, basically actively monitoring them and tracking them. They’re also going to continue paying attention to people in the general population as they receive the vaccine.

Now, it’s very likely that any risks associated with this are very, very low, because vaccines are drugs that are tested to a very high standard. They go out of their way to make sure that complication rates are very low. Generally, these are some of the safest pharmaceutical drugs that we have ever developed. But again, the risk is not zero. There are some people that may experience some complications, and it’s worth trying to take steps ahead of time to try to minimize them, to see what risk factors lead to complications, and then also helping out the folks that do actually have any kind of trouble with them afterwards.

How might having a Covid-19 vaccine change behavior in the US?

These vaccines are very effective against disease, meaning that they will prevent you from getting sick. But we don’t really know how well they prevent infection or transmission. It’s likely that the people who get vaccinated may be able to still spread this virus to other people. And that’s why behavior can’t really change that much from where it is right now.

[The vaccine is] useful in that we can keep people out of hospitals and from dying or getting seriously ill. But precautions like wearing masks and maintaining social distance, those are all going to be important even after the vaccines start rolling out. Even after you and I get vaccinated, we’re going to have to maintain that until transmission lowers enough to the point that we can start letting our foot off the accelerator here. And so that’s why we need to be really paying attention to this.

The other thing is, with vaccines, you don’t want to necessarily use that as an excuse to engage in risky behavior because, again, it’s 95 percent effective, not 100 percent effective. There’s potential for somebody who’s vaccinated to still get seriously ill, so it’s important to take precautions, even for your own sake.

Over time, we do expect some behavior change, things like allowing kids to go to school in person or allowing certain kinds of events or gatherings that are urgently needed, certain kinds of, like, academic programs or other things like that. And then allowing some people to go to work, for instance. Those changes will eventually start to happen as we get transmission down and as vaccination rates go up. But both of those things need to happen at the same time, and that’s going to take some time to do.

If someone’s had Covid-19 before and already has antibodies, should they still get the vaccine?

The recommendations right now are likely going to be that you still get the vaccine. The reason is that while being naturally infected with the virus gives you some degree of immunity and protection, it’s not necessarily targeted. The vaccines are optimized specifically to neutralize the virus and its infection and how it causes disease, whereas with your own natural infection, you will produce antibodies, but they’re more scattershot. They’ll target some of the parts of the virus that cause infection, but they’ll target other parts that don’t necessarily interfere with its reproduction cycle. So it’s very likely that most people, even if they have gotten sick with this, it would be useful for them to still get vaccinated.

How is it possible to still spread the coronavirus after someone’s been vaccinated?

What we’ve seen with the coronavirus in general is that most people don’t get seriously ill. And there’s a number of people that can have the virus and spread it without showing any symptoms at all. That means your immune system doesn’t even mount a response, and the virus doesn’t really do much damage to you.

It’s likely that even after your body gets coached to fight off this infection, the infection might be so low grade that it doesn’t really do anything. It doesn’t even trigger the alarm bells in your body, but it still allows you to spread the virus to other people. And that low level of infection or transmission still poses a risk.

Now, there’s some evidence, especially with Moderna’s data that was just put out today, that seems to indicate that their vaccine actually does lower transmission. So it’s very likely we would actually see a dent in transmission by getting this vaccine, but it’s not as steep of a drop as we saw with reductions in disease. You’ll likely have a lower risk of making other people sick, but not as low as the risk of keeping yourself from getting sick.

Do kids need to get the Covid-19 vaccine? Is it safe for them to get it?

That’s really hard to say because children were explicitly excluded from these clinical trials. In fact, that was one of the big sources of contention during the meeting last week with the advisers to the Food and Drug Administration. They were looking at trial data, and they said that the youngest people in the trial were 16 years old and there weren’t that many of them. [The advisers] were wondering: “Is this a vaccine that we can approve for everyone over the age of 16, or should we raise that to everyone over the age of 18?”

They eventually approved language saying everyone over the age of 16. And it’s very likely that it will be safer in younger people. But with an emergency use authorization, you’re balancing risk and reward, because you’re looking at the potential benefit but you’re also looking at any potential harm.

Now, we know, for instance, that children are much less likely to get severely ill from this virus compared to, say, adults and much older adults. And looking at that risk-reward calculation right now, it seems that it doesn’t really weigh in favor of vaccinating children, [though] that could change in the future, as they do more trials and testing and as we learn more about the disease. But for now, we’re looking mainly at health workers and older adults.

Is the Covid-19 vaccine going to be something like the flu shot, where we need to get something every year?

It depends on how fast the virus mutates. What we’ve seen so far is that it tends to be pretty stable in the parts of the virus that we’re most concerned about. That likely means that protection will last for a few years. Our experiences with SARS and MERS show that protection against those viruses also lasts for a few years. But eventually, the virus will change enough, and you’ll have to restart the process. You might need a booster a few years from now if there is still an outbreak or an epidemic. But it’s very likely that once you get the vaccine, you’ll have some room to breathe easy for a while.

What is most important for people to remember now that this vaccine is out there, and we’re also in this terrible position where the country hit 300,000 Covid-19 deaths?

The [thing] to remember is that our actions do matter. I use the firebreak analogy. The vaccines are like cutting firebreaks, cutting clearings in a forest so that the fire doesn’t spread. But that really doesn’t do much if there’s already a huge inferno that’s blazing. Our goal right now is to reduce transmission as much as possible so that when a vaccine does roll out, it becomes that much more effective.

There’s this herd immunity threshold of 80 to 90 percent of people being immune … where the pandemic starts to fizzle out. But we start to see reductions around 30 to 40 percent. And that can happen if we do a good job of controlling transmission. Our actions right now to try to limit the spread of the virus will make it easier and more effective for when a vaccine does start being administered to people who are in the low-risk pools, maybe next spring and maybe into early summer.


You can listen to this full conversation — and all episodes of Today, Explained — wherever you listen to podcasts, including Apple Podcasts, Google Podcasts, and Spotify.

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