AYESHA RASCOE, HOST:
It really seems like everywhere you turn these days, there's someone who has COVID-19. We're in the midst of a new surge just as the U.S. reaches 1 million deaths. Some people have been taking the antiviral Paxlovid, and some are using rapid tests to monitor their infection. But how effective is that drug and the testing? And what can we expect from this new surge? To tell us more is epidemiologist Jessica Malaty Rivera - welcome.
JESSICA MALATY RIVERA: Thanks for having me.
RASCOE: Tell me about this new surge and the variant causing it. How is it different from all the previous variants and sub-variants we've seen before?
RIVERA: Well, I think that what we're dealing with right now is a combination of factors. It's not that these variants are somehow uniquely different. It's that we're dealing with people who have waning immunity, a lot of people who are not yet boosted, and we know that the booster data shows us that there's significant protection that can be added to somebody who has either never been infected or even previously infected. And a lot of people who were previously infected in the winter surge are kind of coming up at that point where they're susceptible, again, to another infection.
RASCOE: One of the things that can be confusing about COVID is that sometimes people - a lot of people are saying they start showing symptoms of COVID, but then they don't test positive until a few days after that. So when should people actually be testing and start isolating?
RIVERA: If people have been in high-risk environments or if people have had a known exposure to a confirmed case, it's recommended that somebody get tested through a high-quality test - either a rapid antigen test or lab-based PCR - between five to seven days after that. Oftentimes, people are testing, like you said, too early and the test is not detecting enough virus to have a positive. That's especially true for people who are vaccinated and boosted. That's partially because the immune system is doing its job. It's suppressing that infection. But you may still test positive and have a mild infection just a few days into it.
RASCOE: PCR tests are very sensitive, so my understanding is you don't necessarily want to rely on a PCR test or a lab test to get out of quarantine because they'll pick it up much longer than you're actually contagious. Is that the case?
RIVERA: Yeah, that's true. PCR tests are highly sensitive and highly specific tests, which is why they're not used to - kind of - what they call testing out of isolation or quarantine, because you could potentially be testing positive on PCR for several weeks after an infection. That's because it is so sensitive it can detect even fragments of the genomic sequence of the virus even if it's not infectious parts of the virus. And so because of that, rapid antigen tests are actually really helpful in that regard. Rapid antigen tests can help us determine with some, you know - you know, it's not perfect, but with some degree of confidence that - whether or not you're shedding infectious virus. You know, there's been reports of if that second line is dark, you probably have a lot of virus in your body still. And the lighter it gets, the less virus you probably have in your body. So it's, to me, a good indicator, especially if you're testing negative on antigen a couple days in a row - at least 24 hours apart - that you are outside of that infectious period.
RASCOE: What about access to the antiviral Paxlovid? What's that been like?
RIVERA: You know, Paxlovid has - it's been a remarkable drug - just seeing the data. And even anecdotally, I've heard just amazing reports of people having symptom relief within the first couple days of onset of treatment, having - even testing negative on PCR within a couple of days. That just shows kind of how powerful it is to really reduce that viral load in the body and to kind of help clear the virus. That said, it's had a very disappointing rollout. I know that Biden's Test to Treat Program was intended to make sure that everybody had access upon a positive test at participating pharmacies. It would be a free prescription. But I've also heard anecdotally, too, that a lot of doctors are reluctant to prescribe it. That's partially because there hasn't been a lot of training on the drug. There's been a lot of concerns over the long list of contraindications, and people are kind of erring on the side of almost too much caution.
RASCOE: There have been these reports about people getting rebound effects of COVID symptoms after five days of taking the antiviral. Why is that happening? And, you know, what should people do if they're getting these rebound effects?
RIVERA: Yeah, I mean, it could be happening for a variety of reasons. It could be happening because, you know, five days could be too short for some people. And there's been some, you know, suggestion that it could be - require a 10-day course, like two back-to-back courses. It could be because somebody was - started the drug too early in their infection. If it's taken too early, it potentially could not get all of that viral replication that's happening and have more virus kind of remaining after day five where you could potentially relapse and have more symptoms after the fact.
RASCOE: We talked a little bit about this earlier, but this idea of, like, when to come out of isolation. With the omicron variant, people can still have virus levels high enough to be contagious more than five days after symptoms start. But the CDC guidelines say you can come out of quarantine five days after a positive test or start of symptoms. Can you make sense of this? Because at schools and what have you, as long as you don't have any symptoms, you can go back after five days.
RIVERA: We have to remember the fact that five days is not a hard rule, nor is 10 days. What I've been encouraging folks to do is take advantage of the free tests that are provided through the U.S government and take advantage of if you have insurance that they will reimburse you a test. So stock up on those tests so that if you are infected, I would test regularly, and I would not personally exit an isolation unless I had negative tests 24 hours apart, at least two days in a row so that I could know. And also being asymptomatic before I felt confident to kind of reintegrate with other people unmasked.
RASCOE: That's epidemiologist Jessica Malaty Rivera. Thank you so much.
RIVERA: Thanks so much for having me. Transcript provided by NPR, Copyright NPR.
