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Brian Lehrer: Brian Lehrer on WNYC. Yes, the big COVID news in the last day is the new CDC guidelines for people who've been vaccinated. Some of them are straightforward good news, like fully vaccinated people can get together with other fully vaccinated people, without masks or social distancing, they say. Other pieces might take a little more interpretation, which we're going to try to provide now and take your "What can I do after vaccination calls." Back with us is Columbia University virologist Dr. Angela Rasmussen, who identifies herself on Twitter as an excessively direct virologist, and one time Jeopardy loser. Hi, Dr. Rasmussen, welcome back to WNYC.

Dr. Angela Rasmussen: Hi, Brian. Thanks for having me.

Brian: Were you really on Jeopardy?

Dr. Rasmussen: I really was. Yes, in 2014, and I really did lose in Final Jeopardy.

Brian: Is there the one you got wrong that you have dreams about to this day?

Dr. Rasmussen: I do actually, because Alex Trebek actually gave me a little brief afterwards. The clue was this big company was removed from the S&P 500 in 2008, and I guessed the AIG and the answer was actually GM, and Alex said that the big company was actually a clue, and in hindsight it was. I feel pretty bad that I got that wrong.

Brian: Oh, like, AIG isn't a big company. That was mean, Alex, but you think about that--

Dr. Rasmussen: It was, and it's not the big three automaker but.

Brian: I have this from a spelling bee in sixth grade. I would have gone on to represent my school, if only I had known that there was a K in picnicking.

Dr. Rasmussen: [laughs] I have a story about that too, Brian. I actually lost districts in the sixth-grade spelling bee on the word asphyxiate. I'll never spell that incorrectly again. [laughs]

Brian: What is s K doing in picnicking? It's completely extraneous. You may be a one-time Jeopardy loser, but you were multiple times Brian Lehrer Show winner for our listeners. If that's any kind of consolation prize. Listeners, for this segment, we're inviting your calls on the new CDC guidelines for vaccinated people, and other "Ask a virologist questions" for Dr. Angela Rasmussen at 646-435-7280, 646-435-7280. Can you give us a little basic virology first? Fully vaccinated means your second Pfizer or Moderna shot, or your single Johnson and Johnson shot plus two weeks. What's happening in our bodies that takes two weeks?

Dr. Rasmussen: That's a great question. This is how all vaccines work. Most vaccines don't work instantaneously. The two weeks is really so that your immune system can make those antibodies that are going to target the virus after exposure to the vaccine. You don't instantly spring to action as soon as you get the vaccine, your B cells that produce antibodies, and the T cells that coordinate all of your different immune responses actually take a little bit of time to divide and replicate, and make those antibodies, and basically get into fighting form, in case you're exposed to the virus. It does take a couple of weeks for that to happen.

Brian: The CDC says fully vaccinated people can now spend time indoors and unmasked, and not socially distant with other fully vaccinated people, and several people have already asked me, "What about the variants?" Since we don't know if the vaccines protect you as fully from those yet?

Dr. Rasmussen: That's a great question, but all of the data that we do have so far about the variants and this is primarily from clinical trials that have been taking place in South Africa, where the B1351 variant is very prevalent, show that while there is some reduced protection from either vaccines or natural infection, it's not completely abrogated. You don't have completely vaccine-resistant variants circulating, you have variants that are a little bit less effectively neutralized by antibodies produced by those vaccines. In short, the vaccines still work against the variants, they just don't work quite as well, but they're still very protective.

Brian: A fully vaccinated couple in their 90's asked me if they can go back to playing bridge with other fully vaccinated couples in their 90's. The CDC is saying yes?

Dr. Rasmussen: The CDC is saying yes, provided that they are getting together for bridge in somebody's home or in a space that's separate from the public, and that's really more for the safety I think of unvaccinated people, but gatherings like that, with fully vaccinated people are completely fine and very safe.

Brian: Good news for the people who like to play with things that include Trump, that have nothing to do with the President. The next rung down from the CDC guidelines or on the CDC guidelines is fully vaccinated people can spend time indoors with low-risk, unvaccinated people, and I don't understand this one yet. Do you understand what a low-risk unvaccinated person is?

Dr. Rasmussen: I do. The CDC does have guidelines about what constitutes a low-risk person. That would be a person who is younger, and who doesn't have any additional co-morbidities. I think the real rationale for this particular piece of guidance is really so that grandparents can start to see some of their family members again, especially grandkids. I know that my parents, they are excited to spend more time unmasked with my two-year-old niece. I think that a lot of people feel the same way. They've gone a really, really long time without seeing other family members. We know already also that children are not going to be vaccinated for some time to come, and the younger those children are the longer out that will be.

I think that this is a prudent recommendation that really balances the need to be safe and take as much precaution as possible, with the need for people to see their family members and the people that they love in a safe way.

Brian: I think we're getting a caller question relevant to what you were just saying. Let me take Christina in Nassau County, Christina, you're on WNYC. Hi there.

Christina: Hi. Can you hear me?

Brian: I can hear you just fine.

Christina: Hello?

Brian: Hi, Kristina. Can you hear me? What's your question?

Christina: Yes, I have three grandchildren ages five to 13. From what I just heard, because I was calling at the same time, the vaccination of those children is far out in terms of timing. Should I be very cautious like I've always been? I double mask when I'm around them. If we're outside, I can take my mask off. What's the protocol for this at this point to see my grandchildren?

Dr. Rasmussen: If you've been fully vaccinated, the CDC is recommending that it is okay for you to see your grandchildren without a mask on. I would like to say though that this really does come down to personal comfort and your personal tolerance for risk. This guidance is making the assumption that those grandchildren are going to be low risk. They don't have things like asthma, or diabetes, or any of the other comorbidities that would put somebody in a higher risk. It's saying that even if there is a chance that you become infected asymptomatically, you won't experience disease because you've been vaccinated, but in the slight possibility that you could transmit the virus to them, that they're not going to get very sick.

Not everybody is going to be comfortable with that level of risk, but if your grandkids and their parents are okay with that, then yes. In your own home two weeks after your second shot or your final shot, you can get together with your grandkids and spend time with them without needing to wear a mask or being especially conscious of social distancing.

Brian: I think what you just described-- Christina, thank you for your call. I hope that gives you a solid answer. What you just described is sort of the now that there are vaccines ironic standing on its head of who protects who, during the pandemic. It used to be that people didn't get together with their grandparents to protect the grandparents. Now that the grandparents is the generation getting vaccinated, if they're not getting together with their grandkids, it's to protect the kids. Am I hearing this right?

Dr. Rasmussen: Yes, you are hearing that right. That's why grandparents have been prioritized for vaccination is because we know that being older is a risk factor for having more severe disease with COVID-19. With that said, children are not completely immune from getting SARS-CoV-2 infection, and some children do have very serious illness. It's rare, but it does happen. That's why it's really important to emphasize that this does come down to a personal decision about what level of risk you're comfortable with.

If you're not comfortable with the risk that's presented to children, then you should continue to mask and distance and so forth. I still think though that it probably is okay with masks on and distancing observed for kids to get together with their grandparents still. If you're not comfortable with that risk, then just continue to take those additional precautions. You don't have to completely avoid your grandchildren if you're really dying to see them, which I know many, many people are.

Brian: One more follow-up question to this point before we go back and take some more calls. The guidelines from the CDC yesterday are not so much to protect the vaccinated person, but really to protect the unvaccinated person, in case the vaccinated one has asymptomatic COVID and is breathing it out. I see you tweeted that we don't yet know if vaccination prevents transmission, but there are reasons to think it does. Can you go over some of that evidence?

Dr. Rasmussen: Yes, absolutely. Way back to when the vaccines were actually still in development, they did preclinical studies. These are studies in which they infect vaccinated monkeys with SARS-CoV-2. In those animals that were vaccinated, all of the vaccines were not completely protective against infection, but the animals that did get infected had lower levels of virus, and there were fewer of those animals that got infected after challenge compared to the control group.

Way back to when we were doing studies in animals, these are a normal part of the vaccine development process called the preclinical stage, we knew that the vaccines would likely reduce transmission. Now, that some of the trials have started to read out, people are actually looking at the rate of asymptomatic infection in people who've been vaccinated. Now, the trials themselves didn't look at infection as the primary endpoint. They looked at symptomatic COVID-19.

The reason for that is that the most important metrics, the thing that will keep people alive is seeing whether the vaccines can protect against disease. It also takes longer to look for whether the vaccines can prevent infection because you have to repeatedly test people, especially if they're becoming infected asymptomatically. They can't report symptoms that they're not having. We didn't look at this in-depth in the clinical trials, but now we are starting to do so.

It looks like most of the vaccines for which there's data also do reduce the number of asymptomatic infections, which shows that they are at least partially protective against infection. If they're partially protective against infection, then that means that people will not be getting infected, and therefore can't transmit it to other people. The problem, what we don't really know right now is that we don't know what the effect size is.

We can't put a number to this. We can't say that it's 60%, 70%, 80% effective at reducing infection or protecting against infection. We can only say that it likely does. The data is pointing in that direction, but we can't assign an actual number to it. We can't tell people what the risk actually is. People should know that that we will be getting that data soon. People are working on this very actively. I would imagine that in the next month or two, we're going to have a lot more clarity on this particular issue.

Brian: Anna in Manhattan, you're on WNYC with virologist, Dr. Angela Rasmussen. Hi, Anna.

Anna: Hi, Brian. Thank you for taking my call. I am fully-vaccinated myself. I listen to the CDC guidelines, them talk about not planning any flights. However, I have a number of friends, European, so Norwegian, like myself, who are planning to make trips to Europe pretty soon, as soon as they raise their immunity, to countries where we know their state of vaccination is not as good here. In fact, the EU has made a bit of a mess in terms of vaccinating the population. Is that a good idea to consider at this point, or when can we actually start thinking about things like that? Thank you.

Dr. Rasmussen: Yes, of course. I think that for the people who are fully vaccinated, it's fine for them to go on a trip to Europe. The issue that they're probably going to run into immediately is that there are travel restrictions for many different countries, including the European Union. Some of this is based on coming from countries where certain variants are circulating in large numbers, and that's going to differ from country to country.

I think in some places, it's going to be still very difficult to go on an international vacation to a country that's not allowing people to come in unless there's an absolute necessity, and they can somehow justify their trip. I think though that that guidance is going to change and those travel restrictions will be relaxed as the situation changes in all these different countries. As transmission goes down, as immunization goes up, as more people get vaccinated, countries will change their travel policies accordingly.

I am so optimistic that by the end of the year, we will be able to travel for leisure and fun that I have actually booked a flight to Italy for a vacation I was supposed to take last year with my parents in November. My parents are both fully vaccinated now. I will be fully vaccinated by then I hope. I'm hopeful that we will be able to go. Of course, I'm willing to cancel that trip if the situation does not permit international travel, or you can't do that safely, but I'm optimistic that we will be able to travel more internationally by the end of the year.

Brian: Going down the next rung or to the next rung on the CDC guidelines ladder, it says vaccinated people should continue to wear masks when in public and continue to avoid crowds. I guess that includes crowds on international airline flights. How do you understand their definition of "avoid crowds"?

Dr. Rasmussen: I think "avoid crowds" means the same thing that it does right now. Unless it's absolutely necessary, don't go to a place where there are going to be a lot of people from outside your household gathering together. That could be a restaurant, a bar, a party, an international flight that's not absolutely necessary. Avoid situations in which you're going to be in close proximity, probably for a longer period of time, possibly in an enclosed space with a number of people who are outside of your household. That's how I interpret that.

I think that some of this is not so much again because of the risks that's presented to vaccinated people. I think the risk to them we know is low because these vaccines are pretty effective at preventing disease. I think the risk is-- It's really two risks, the potential unknown risk to people who are not vaccinated in public, as well as the fact that we just haven't been able to distribute vaccines equitably yet. There are still large disparities in who's able to get a vaccine and who's not.

I think that we need to be very careful about creating a two-tiered society in which people who have been fortunate enough to get access to vaccines are suddenly able to do a lot of things that people who have not yet been able to access them can't. I think that for those two reasons, it's very prudent, I think, for the CDC to just be cautious about this and to ease into relaxing these restrictions. I think that's a smart thing to do from both a social and a public health perspective.

Brian: One more call. Priyanka in Brooklyn, you're on WNYC. Hi, Priyanka.

Priyanka: Hi, Brian. Thank you for taking my call. My question is about the difference in immunity between those who had caught the Coronavirus and the vaccine. Because the CDC's guideline right now is allowing these freedoms to everyone who has the vaccine, but isn't that based on bureaucracy of immunity rather than the scientific fact of it? Is there a way to somehow-- Yes, please go on.

Dr. Rasmussen: I was going to say that's a great question, Priyanka. One thing that scientifically this is based on is the fact that vaccines produce much higher antibody responses. If you look at somebody who's been vaccinated versus somebody who's recovered from SARS-CoV-2 infection, in the vaccinated people, you're going to see very high levels of what are called neutralizing antibodies. These are antibodies that completely prevent the virus from infecting cells and render it noninfectious.

If you look in people who were previously infected, you're going to see a much larger range of those neutralizing antibodies. You're going to see some people who have very high levels, but you're also going to see some people who have very low levels of potentially undetectable levels. We know that the vaccine reliably in most people induce these high levels of immunity and that it's more variable with people who haven't been immunized but have immunity from natural infection.

Now, that said, we do know that most people who were infected do have what's called durable immunity. You can measure immune responses in those people months out after they've recovered from their infection, which is pretty consistent. What we know about immune responses for other viruses, but right now the data just suggests vaccines produce these reliably consistent strong immune responses. Whereas a natural infection could be more variable. I think that's where this recommendation comes from.

Brian: Guess what we are what's supposed to be the end of our time, but we're going to extend for a minute because we have, coincidence, vaccination breaking news. New York State has just announced on Twitter that people 60 years of age and older, it was 65 now it's going to be 60, can be vaccinated beginning tomorrow, March 10th. In addition, government employees, nonprofit workers, and essential building service workers are eligible for COVID-19 vaccines beginning next Wednesday, March 17th.

I'll say that again. The age limit goes down to 60 as of tomorrow in New York State plus government employees non-profit workers-- I guess that would be everybody who works at WNYC, and essential building service workers are eligible for COVID 19 vaccines beginning next Wednesday, March 17th, Dr. Rasmussen, your reaction?

Dr. Rasmussen: My reaction is that's wonderful. I think that we need to be able to vaccinate as many people as we can as quickly as we can. Anytime any state, including New York expands the pool of people who can access vaccines the better. That's wonderful news.

Brian: I saw it on Twitter. I'm told now the governor had made an in-person announcement or maybe it was an over Zoom announcement, who knows, but it came from the governor's mouth. All right. Dr. Angela Rasmussen Virologist from Columbia University Mailman School of Public Health. Thank you so much for all the information on the new CDC guidelines. It's all very encouraging.

Dr. Rasmussen: Oh, it's my pleasure, Brian. Thanks for having me.

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