COVID-19 Update 3/17: Vaccine Effectiveness, Antibodies, and More

On this week's COVID-19 update, Dr. David Pong fills in for Dr. Bishop and provided an update on vaccination numbers, the effectiveness of vaccines in the real world, the durability of antibodies as far as we know, and the prospects of wearing masks and washing hands long-term to prevent infections beyond COVID. Watch the video below and read on for a transcript. 

Vaccination Numbers

If we look at the Virginia numbers right now we've vaccinated almost 2 million people with at least one dose. That's 21% or so of our population who's had at least one dose of the vaccine. Now, we think from some of the study data, that one dose of the vaccine will probably get us something like 80% or so of the protection that is available from the vaccine. Maybe less with some, maybe a little bit more.

When you get the second dose, it will take you up into the 95% range with the Moderna or Pfizer vaccines. We're probably looking at more like 10% kind of numbers in the population of people that have had two doses. So most of the people have not. Perhaps on the order of 10% of the population maybe a little higher in some settings has been infected, and those people should have pretty good immunity.

Right now, we think that acute infection carries immunity that probably lasts for something on the order of six months or so. And we're hopeful that that's what we'll see out of vaccination as well.

So right now in Virginia, as an example, and it's similar across much of the country, about 20% of the population has been vaccinated with at least one shot. Therefore, we have something in that 15 to 20% of the population range who are immune. So if I go out into the public, if I'm walking through the grocery store, something like a quarter of the folks, a fifth of the folks are immune and the rest of the folks potentially are available, either as someone who could give me the virus or someone who, if I carry it, I could give it to.

Vaccine Effectiveness in the Real World

So these guidelines that have come out from the CDC are written in that context. It's knowing that we still have the majority of the population who are not immune and we're trying rapidly to vaccinate, particularly the highest risk people, to help them develop immunity.

So, two studies to think about, or at least reports, the first one is from the NIH Director Francis Collins, and he has an ongoing blog and he writes beautifully in terms of giving brief explanations for research that's being done.

And his most recent one from March 9th, he described a study done in Israel. There were 600,000 people who were vaccinated out of 9 million in the population, and they found that the risk of symptomatic COVID-19 dropped by 94% in the week after vaccination. Dramatic and very similar to what was seen, this was with the Pfizer vaccine and it was similar to what was seen in the actual formal studies. So nice to see that in the real population that we actually can see similar results in a real population study as we did in the more formal original studies that went through FDA.

It looks like in that study, they were able to also show that during a time when they were having a significant rise in their caseload, they had their third and largest rise or surge in COVID-19 during the window of this study, which was from the end of December through the 1st of February, and at that time they also had the B117 UK variant of the virus, went from being a minority of the cases to being the dominant vaccine strain in Israel.

Despite that, and during that timeframe, vaccination was highly successful. So again, in 94 to 96% effectiveness at preventing asymptomatic or symptomatic COVID disease. It turns out they also studied this in older folks, and in folks over 70, the vaccine performs almost identically to what we see in younger folks. So really exciting to see, in a real world population, that we can see the kind of efficacy of this vaccine that we expected, hoped for from the more controlled studies.

CDC's Recent Guidelines on Post-Vaccination Activities

So based on this sort of thing, the CDC's most recent guidelines that Dr. Walensky put out on, I think this was published in JAMA on March 10, these guidelines are trying to allow us to have a little more flexibility.

And I guess the way I think about it, you know the guidelines as any of you saw describe vaccinated people, fully vaccinated people, those who are two weeks after completing their vaccination series, either two shots with the mRNA vaccines or one shot with the Johnson and Johnson.

When you're two weeks out you will have made the antibodies that you're going to make and we believe that there's going to be some window of protection, perhaps as long as six months or so, maybe longer, we don't know that one yet, but during that time, you know, very high level protection.

And the guidelines would say now that people who are fully vaccinated can gather in small groups without masks and without social distancing because the likelihood of transmission is so low in a population like that.

Again, imagine that if we bring together 10 people, all of whom have been vaccinated, the likelihood of any one of them being able to carry vaccine, not having good immunity, it's something on the order of one of those people. It's roughly four to six out of a hundred who would not have developed immunity with the vaccine. So, perhaps one in 10 would be able to either acquire the virus or transmit the virus.

So you can imagine that bringing those people together starts feeling much safer because you now have a group where it's very unlikely that anybody in the group can either give it away or gather the virus.

Certainly if you have a group of people who are vaccinated, even relatively high risk people who are vaccinated or older people, they really are quite well protected.

The guidelines also talk about bringing together vaccinated and unvaccinated people. So they say you can come into a single household and you have a group of people in a household who are unvaccinated and it's okay to have them get together with the vaccinated crew.

But then they go on to say they don't recommend having large group gatherings or having large events like sporting events. They recommend continued use of masks and distancing on public transportation or in settings with groups.

And again, I think it kind of makes sense, you know, the larger the group, the more likely it is that you could find somebody even among vaccinated people but certainly among unvaccinated people, the more likely it is you would find someone who is either able to give you the virus or able to acquire it.

The lower risk the population, the more safe it seems, because even if you were to be with someone and actually a viral transmission event occurred, as long as everyone is otherwise low risk, the likelihood of hospitalization or dying is low.

I think that the guidelines make a lot of sense. And I think that for right now it's very reasonable for us to think about gathering small groups, particularly a vaccinated or low risk unvaccinated people together.

But I do think that as the groups get larger, or as the contacts among different members of the groups get larger, we all have to stop for a minute and think about what's really important to us, right?

So, it's not just, can I take this darn mask off? It's thinking about how bad would it be if any of the people here actually got COVID? How bad could it be? So is my father, someone who it's worth it to me to be able to be with him with a mask off, knowing that if he got sick with COVID it could have a very bad outcome.

And how do I feel about some of the kids knowing that we have this multi-system inflammatory process that can occur in kids sometimes, it's not very common, but it's a terrible thing when it does. So trying to think about, you know, who in the group is at higher risk for a bad outcome.

Someone who already has compromised lungs, compromised heart, compromised immunity, those folks, it may still be worth putting on the extra protection of a mask and keeping some distance, even if we're vaccinated.

What to Watch Going Forward

But generally this is very encouraging stuff. The thing I would be watching for as we go forward is what did the case rates do?

Right now in Virginia, our positive test results compared to the number of people tested is only 5%. It's continued to fall nicely.

And as long as that number is falling and staying low, I think this sort of thing makes all the sense in the world. And hopefully as we get into the summer we can even do more with it. We can actually open up our businesses more, travel a bit more, feel more comfortable with that.

I do think it will be important to watch those numbers. If we start seeing rises, for example, after different holidays, if we start seeing rises in the numbers, we may have to step back and put up a bit more protection until we understand why that's happening.

Monitoring Variants

Right now in the United States we're just starting to ramp up our ability to screen the viruses that are isolated to understand their gene sequences to be able to understand what's going on with variants.

And so until we're able to do that really well, it's going to be hard for us to understand when something like B117 or the B135 variants are becoming more available for transmission. We know that those variants are more easily transmitted and therefore we may have to pay attention to that.

The current vaccines may not work as well. We may and likely, we'll find ourselves doing booster vaccines in the future for the same reason that we boost flu vaccines every year. There will be mutation as long as we have so many infected people.

Remember that even though the rates are all falling, we're still at a very high level of infection across the country. Thousands of people every day are acquiring this infection and every one of them is an opportunity for creating variants and mutations. So, we still are at a place where we need to be careful that way.

Antibodies After 6 Months? 

"The first question, does this mean that the thinking now is that a person who has had COVID has antibodies for about six months?"

I do think that that's true. I think that most of the people who have been studied who have had acute COVID do have protective antibodies that seem to be able to neutralize virus from a new exposure.

And I use six months because there have been some studies that suggested it was shorter. And there probably are individual people who will have less than six months of protection from their experience. And there have been folks out in the nine month range that have been identified.

It's believed that asymptomatic COVID will provide less of an immune response and perhaps lower antibody levels. And people who have gotten sicker probably will have a better immune response assuming they had a good immune system.

So we also have to factor in, there are some people whose immune systems don't work very well. They've either been poisoned by chemotherapy. They've had a disease that is hard on the immune system. And for those people, sometimes they're having trouble getting out of their acute infections and certainly you would expect they might not make as many antibodies.

Unfortunately, we're still at a point where we can't measure that. We can tell you whether you have antibodies or not reasonably well, but we can't measure how many. If you asked me, am I immune to measles? I can do a measles test, can draw blood, and tell you you have a lot of antibodies and that you would be protected.

And we eventually we'll get to that with COVID, but right now, not yet. And so we're a little frustrated because we can't show you whether you have immunity, even if we can show you that you have antibodies.

We're not certain that that any individual we can say you have immunity. But statistically it's a high probability. Again, probably on the order of 90 to 95% of the time a person who's been through acute COVID will have several months of protective antibodies.

The follow-up question was, "I'm not sure I heard you correctly. Did you say that once were vaccinated we're protected for about six months? Is that all?"

And again, the real answer is we don't know. We haven't had people vaccinated long enough to be able to answer that question. The assumption is that the vaccines are not going to be forever.

The assumption is that even if the vaccine, if there is not a mutation, that it's likely that we would eventually need to boost. And the reason for that kind of goes back to how things work.

The reason we don't tend to develop great immunity to colds, which is another coronavirus often, is because there's mutation with it. But also because we see a cold virus periodically, we make some antibodies to it, and then when we don't see one for a while, we don't keep making high levels of the antibody, similar to influenza where over years of vaccinating and periodic infection, we have a library of antibodies.

And when we boost that with a vaccine or when we see influenza, most of us will be able to make a pretty decent immune response and most of us won't end up in the hospital.

But this virus, this COVID, is a brand new virus. And so we don't have a library. We don't have any foundation that we're building on. We're starting from scratch. So the likelihood is high that we'll make a good immune response, we see that 95%, right, but the likelihood is also true that if you don't see it again either as a booster or an acute infection, that eventually you'll slow down the production. You could imagine that if we made high levels of antibody to everything we ever saw, eventually we'd be a big bag of antibodies because we have to have ways of slowing down the processes that we don't need.

So right now, this is likely to be a thing that's a temporary benefit. We don't know exactly how long. Again I use a six month window because there is some data out there that looks like that. It's hopeful that we'll see longer but it would not surprise me at all if somewhere in the nine to 12 month range we were looking at boosters, both to account for the variants that are out there as well as to account for waning immunity.

So what would I do, right, with that? I think right now, I'm feeling a whole lot better when I'm with other people who've been vaccinated. It feels like it's much safer and reasonable to have small groups together.

I think that as we look at those groups and, if people are otherwise low risk and healthy, it feels very, very safe to me. If we have folks in those groups who are higher risk then I think it's more important to stop for a moment and think about the value of taking off the mask or getting close versus the downside of doing that and make decisions.

Unfortunately, we're certainly not at a point where me as a doc or the CDC as our government can tell us with certainty what's safe or not safe for any one individual. We just, and again, we never really get there. We always want that, but we never really get there.

I think where we are is that we can tell you statistically that things really are looking quite good with vaccination. I think that vaccines are very safe. It's extraordinarily unlikely that you'll have a serious reaction to getting a vaccine. You may feel sick for a couple of days, but the likelihood of ending up with something dangerous from a vaccine is almost zero.

And the protection is dramatically better than we ever hoped for, right? I mean, early on before any of these vaccines came out, the bar that was set was, if we could get something on the range of 60% of people who got the shot to make antibodies that would be success. And here we are with vaccines that are in the mid-nineties. It's quite dramatic.

So I do think it's an exciting thing. I do think it's a very good thing. I encourage all of you to get vaccinated with whatever vaccine is available to you. If you have a choice and have had acute COVID, you might consider the Johnson & Johnson vaccine, because there are some interesting studies that show that the antibody response in people who had acute COVID when they become vaccinated is pretty big. And so we really see a dramatic rise in the number of antibodies produced in those folks.

And you may find that your second shot, let's say if you had acute COVID, you get two shots of Moderna or Pfizer, that second shot may make you feel pretty uncomfortable. Again, really not seeing serious side effects but you may be more uncomfortable and you may end up with a fever and have to miss a day of work or something with that. So you might be a person who could kind of have an easier time of building an antibody population with the Johnson & Johnson vaccine when that's available to you. So, something to think about.

Long-Term Plan for Masks and Distancing

So let's see, one other thought I suppose, is, you know what are we going to do long-term with the masks and distancing at all?

I think some of you have probably heard me and others say this, it's been a dramatically different flu and cold season for us doctors.

I, normally, during the winter season, I'm hearing from folks with colds and treating sinus infections commonly, writing antibiotics for sinus infections a few times a week. And I'll bet I wrote a half dozen antibiotic prescriptions through the whole winter for sinus infections. Very, very unusual.

We're seeing people with allergies who've had dramatically less symptoms than they had previously seen. We're certainly seeing a lot of people, many fewer people, with respiratory infections that are non-COVID related.

And the flu season was very quiet. I think I wrote for perhaps three or four courses of an anti-viral for influenza this year. Again, in a typical flu season, we'd be doing that every couple of weeks in this population. So it is something to think about, even if COVID is quiet as we get to the other end of the year and we start into our next flu season, I think it's really likely that I will be wearing a mask next cold and flu season and doing that when I'm in the grocery store and doing it here in the office.

I think it's a very small price to pay. Do we have to do it with everyone we interact with at that time? I don't know yet. I'm hopeful that by then we'll have so many of us vaccinated that we won't need to do that for COVID.

But it may make sense to do that during cold and flu season anyway, even if it's not just specifically for COVID. The other one that I think about is hand-washing. This has made hand washers out of many of us. We should all be hand-washing. Soap and water is remarkable in its ability to prevent infections, whether we think about bacterial infections or viral infections.

And even when COVID settles down don't stop washing your hands. I think that's hugely important.

Wrapping Up

Going to wrap up, I don't have any more questions that I see here. I surely appreciate your time and hanging in there.

Again, I suppose if I was to try and put it in just a few sentences, it's exciting to see that vaccination seems to be accomplished with hardly anybody having serious reactions.

It's exciting to me that both in the studies and in the real world experience, even at a time when some of the variants are rising, we're seeing high levels of immunity generated from vaccination. And I do encourage you to get vaccinated when you can.

I'm excited to see that, you know, most folks I think are continuing to take a thoughtful approach to this and not be terribly reactive with the idea that either we're all-in with masks and distancing or it's Woodstock again.

I really think that it's important to stop and think about who you're going to be with and what the setting is and do what's appropriate for the situation. I think we do that with a lot of other areas in our life. We think about the equipment we might wear to go rock climbing. If you're doing a climbing wall and you're going to be up 10 feet in the air, it's different than if you're going to be climbing up the face of El Capitan, you know, it's a different kind of situation and each one merits its own evaluation.

And you're all smart, you can figure that out. We're obviously happy to help you think about it. When in doubt, I would continue to put a mask on. I think it's a pretty small price to pay and we can do almost everything we want to do with them on anyway. Anyway, I wish you all well. I hope you're able to get vaccinated soon and I hope everybody stays healthy.