Vaccine of interest for travelers to endemic regions

Host Amber Smith: Upstate Medical University in Syracuse, New York, invites you to be "The Informed Patient," with the podcast that features experts from Central New York's only academic medical center. I'm your host, Amber Smith.

A new vaccine is available for a virus called chikungunya. We'll learn who needs to consider this vaccine and what chikungunya is with my guest, Dr. Katie Anderson. She's the health commissioner for Onondaga County and a faculty member in microbiology and immunology at Upstate.

Welcome back to "The Informed Patient," Dr. Anderson.

Katie Anderson, MD, PhD: Thanks for having me.

Host Amber Smith: Chikungunya is another virus that's spread by the bite of an infected mosquito. What else can you tell us about chikungunya?

Katie Anderson, MD, PhD: Chikungunya is yet another of new viruses that are emerging in recent years. It's been known for several decades and previously was isolated to areas of Africa and Asia, but there was a big epidemic of it. It swept through Central and South America in 2013, 2014, and caused a lot of disease. It's a mosquito-borne virus, similar to other ones we've had emerging -- West Nile, dengue, Zika -- but it's in a different family. It's an alpha virus.

And the name is of particular significance to note. It has nothing to do with chickens. It relates to an (African) Makonde (language) word from where it was identified in Africa and refers to the severe joint pain that you get with chikungunya, and it translates to "that which bends up," meaning you're so stooped over when you get chikungunya, it earned this name. But it can be a quite significant, painful acute illness.

Host Amber Smith: So do all mosquitoes potentially carry this virus?

Katie Anderson, MD, PhD: It's important to note that it's spread by the same mosquito, the same pesky mosquito, that spreads yellow fever, Zika, dengue and chikungunya now, as well, and who knows what other viruses to come: Aedes aegypti, which is a major public health pest.

It's also spread by another vector called Aedes albopictus, which is why you can sometimes see these viruses spreading into areas that are more temperate, so parts of Europe, for example. The percentage of mosquitoes who may have chikungunya is generally quite low. But during epidemics where there have been these massive, explosive epidemics of chikungunya -- for example, in Latin America, 10 years ago or so -- the percentage of mosquitoes carrying the virus could be much higher, on the order of 10% to 20%. But typically now, we believe it's relatively low.

Host Amber Smith: Do mosquitoes potentially carry more than one of these? Could there be one that has yellow fever and chikungunya and dengue?

Katie Anderson, MD, PhD: That's been hard to study. But we know that sometimes when the conditions are right for a chikungunya epidemic, the conditions can be right for a dengue epidemic because they're spread by the same mosquito. So when the conditions are right for the mosquito, we certainly can see patients who can have both viruses at the same time. So we can presume that mosquitoes can also be co-infected.

And they live for about a month. So if they have the virus, they could pick up other viruses, and then they could be at particularly high risk for spreading disease.

Host Amber Smith: Now, how does the mosquito get infected? Are they born already infected, or do they have to, do they get this from another animal?

Katie Anderson, MD, PhD: That's a great question. So we believe that there is some, what's called vertical transmission, where it can be passed down within mosquito generations. But most of it is picked up when the mosquito feeds on an infected person. And Aedes aegypti is a particularly significant health threat because it only feeds on humans, by and large.

So you have an infected human who infects the mosquito. And then it takes about one week for the mosquito to be able to infect someone else. It has to go through their gut to their saliva, and then it'll infect new people.

Host Amber Smith: Does it spread from person to person? If someone is infected with chikungunya, do they spread it to their family members?

Katie Anderson, MD, PhD: No. We don't believe so, and we haven't seen that. It's a blood-borne virus. There have been a few rare instances of laboratory workers becoming infected with chikungunya when they're working with it in the lab, as well as rare health care workers who maybe had a needle stick. But it requires blood transfer, or infection within a mosquito.

Host Amber Smith: Where are the problem areas or the countries that have had the outbreaks that we need to be concerned about today?

Katie Anderson, MD, PhD: So before 2013, which is when we had the huge epidemic in the Americas, it would've been just a handful of countries that we knew had a chikungunya case here, a chikungunya case there. It's very similar to Zika in that regard.

But in 2013, there was the arrival in the Caribbean and then explosive spread throughout Central and South America. And now over a hundred countries and territories have experienced chikungunya transmission. And that includes, again, it followed the same distribution of the Aedes aegypti mosquito, which is most of the tropical and subtropical regions of the globe.

But one of the biggest challenges with chikungunya is that the areas that are problem areas, so where you need to be particularly concerned for travel, it can be very unpredictable. And it can be very hard to counsel people on how to avoid chikungunya exposure. So we think that there are many regions of the world where chikungunya continues to circulate, but probably at relatively low levels.

In contrast, there are places like Paraguay last year, where they had a massive, explosive epidemic where the risk would've been much higher. But it's very unpredictable, this virus.

Host Amber Smith: Is there transmission in the United States to be concerned with, or is this mostly people traveling to more tropical areas?

Katie Anderson, MD, PhD: The risk of chikungunya -- and the same would follow with dengue and Zika -- is largely within travelers. And that's not to say we don't have the mosquitoes here in the United States, because large parts of the U.S. Have Aedes aegypti, large parts have Aedes albopictus. We think that we have a couple things going for us in our favor in that the structure of our housing, the fact that we by and large have screens on our windows, that we have air conditioning units, for example, often, are protective factors. So even though we have the vectors here, we don't tend to see widespread distribution or circulation of any of these viruses.

But that said, when chikungunya was blasting through the Americas in 2013 and '14, we did have limited transmission in Florida, of just maybe a dozen cases, suggesting it's possible, but we don't think we have the right conditions for massive epidemics just yet.

Host Amber Smith: This is Upstate's "The Informed Patient" podcast. I'm your host, Amber Smith. I'm talking with Onondaga County Health Commissioner Dr. Katie Anderson about the chikungunya virus and the new vaccine that's available.

Now, let's go over the symptoms of chikungunya in a human. How soon after infection would someone start noticing symptoms, perhaps?

Katie Anderson, MD, PhD: It's typical to know when you've been exposed because it typically comes through the bite of an infected mosquito, which in many places of the world is a very common occurrence. But about four to seven days after you're exposed, you'll start to develop symptoms which can be very similar to many other viral illnesses.

So the individual may have a high fever that comes on quickly. The joint pain is most likely the most significant and debilitating aspect of this infection, typically in the hands and feet, and individuals may also have muscle pain, headache, nausea, fatigue and rash. Typically, this acute phase, at least the fever, will resolve within the matter of days, two to three days. The problem with chikungunya is that we think that it doesn't become a chronic illness, but the joint pain symptoms, in particular, can be profound and can continue for weeks to months to years.

Host Amber Smith: How difficult is it to get a diagnosis?

Katie Anderson, MD, PhD: I would say quite, quite difficult. And the reason for that is that the symptoms that we're describing overlap a lot with dengue. They overlap with a lot of other common tropical infections. And these are occurring in areas that don't have a lot of laboratory capacity. So there are tests for chikungunya. For example, you could do what's called a PCR (polymerase chain reaction), where you look for the virus in the blood, or you could look for chikungunya antibodies.

But that's not commonly done in most of the places where people would get this virus. So it's typically a clinical diagnosis, which would mean a physician would say, this looks like chikungunya, so I'm calling it chikungunya. But again, it overlaps a lot with other viruses and other diseases.

Host Amber Smith: How is it likely treated?

Katie Anderson, MD, PhD: Well, the treatment is limited to supportive care. There's no specific antiviral for chikungunya, just like there isn't one for dengue or for Zika. Treatment is supportive, so you treat the joint pain, you treat the fever and try to support the person's symptoms as they recover from this acute phase.

For certain individuals -- and it's a minority, but it can be a significant proportion -- maybe 30% of people who will go on to have extended, prolonged, debilitating joint pain. And those folks may benefit from seeing a rheumatologist and going on more specific treatment for the arthritis.

Host Amber Smith: So I was wondering if it seems like arthritis, or if there's something different about this type of joint pain.

Katie Anderson, MD, PhD: I think that it would be rather similar to other types of joint pain, but a rheumatologist would be able to work with the person and distinguish it from, say, rheumatoid arthritis or lupus on the basis of labs, and also the history of travel and a fever, most likely.

Host Amber Smith: So without a precise treatment or medication to treat chikungunya, prevention, I guess, is probably the best way, to try to avoid being bitten by mosquitoes to begin with. But let's talk about this vaccine. What do we need to know about it? What's it called?

Katie Anderson, MD, PhD: It's called Ixchiq.

Host Amber Smith: Ixchiq. Is it for adults or children, or both?

Katie Anderson, MD, PhD: So this vaccine was just approved by the FDA in recent months and then recently got its designation from the ACIP. So to go over the pathways for vaccines again: So the FDA (Food and Drug Administration) will review, for the United States, the safety records, the immunogenicity, how well it seems to work, the efficacy, so in terms of how much disease it prevents, and then it will give a regulatory approval. The ACIP (Advisory Committee on Immunization Practices), which is the next meeting that happened somewhat recently, is when the CDC's (Centers for Disease Control and Prevention) advisory board will review how they recommend this vaccine be used in the United States.

So the recommendations are specific for our context. And the recommendation for Ixchiq from ACIP was that it's for adults, and it should be considered for individuals who are traveling, and traveling to a place either with an outbreak, so that would be like Paraguay last year, where the risk is really high, or if they're going to a place where there was chikungunya transmission in the last five years, and who are particularly high risk to be exposed to mosquitoes or have a bad outcome. So it's a very specific and somewhat intentionally vague description for who should get this, really just prompting a discussion with a travel medicine physician.

Host Amber Smith: How long does it offer protection for a person?

Katie Anderson, MD, PhD: The goal of the vaccine is long-term protection. But I think in the context of this vaccine, and this relates back to the somewhat unique epidemiology of chikungunya, it had a somewhat unique pathway, where there are still things that we're learning about it in terms of how long the protection may be.

So typically when you're evaluating a vaccine, first you check for safety. In small trials, it passed that. You look for immunogenicity, which means that it makes an immune response to what you're trying to protect. It did that, in the period after vaccination occurred. And then the next step would typically be to look and see how well does it prevent disease when given to large numbers of people, on the order of thousands.

We can think back to COVID, again, an atypical example, but there certainly were efficacy trials to prove how well it worked. For chikungunya, it is near impossible to try to identify where the next epidemic may be and how you would find enough people to be able to say it's efficacious, or that it works very well.

So based upon the antibody response that the vaccine generates, and the safety, the fact that at two-year follow up, the level of the immune response is still quite high, at 95%, there's a presumption that it will work well to prevent chikungunya. I think that's a fairly reasonable assumption, but what comes next is the trials for all of these, this Valneva Austria vaccine, Ixchiq and others that are in development. They can be licensed without these efficacy data, but that needs to come and be proven next. So I think there's more to come in terms of how long it protects and what exactly we know.

Host Amber Smith: At this point, are there any precautions, or can this be given to anyone safely, or are there any conditions that a person might think twice before they get the vaccine?

Katie Anderson, MD, PhD: This one is a live attenuated vaccine. So there's a wide variety of different vaccine types we get. The fact that it's live attenuated means that it's similar, for example, to (the vaccine for) measles, mumps and rubella. So there's certain people who should not get this, people who have a compromised immune system, for example, or people who take medications that suppress their immune system, because it is a live vaccine that should replicate in your body and cause an infection, really a low level infection, to be protective. So they would be contraindicated (advised against).

And then it should be noted that as with all vaccines, there are some minimal side effects that are noted with this, like some mild joint pain, some headache and some occasional fevers.

Host Amber Smith: Well, if someone thinks that they qualify for this, and they've got travel coming up to an area that might be problematic, where do they get the vaccine?

Katie Anderson, MD, PhD: The vaccine will most likely be available through travel clinics. And my understanding is in our area here in Central New York, they're not available yet, but may be coming to travel clinics in the coming weeks or months.

And I'll say that if I was a travel medicine physician, and I've done some of this in the past, I would be most likely to recommend this for people who are traveling to a place, just like the ACIP says, clearly if there's a large epidemic going on, and then the rest would come down to how long are you going for? What is the level of the health care system to the place that you're traveling to? If you got an illness that made you really sick for a couple of days, how would that impact that trip that you're taking? And have kind of a discussion, hand in hand, with an assessment of how well insurance will cover this, because this vaccine may be on the order of $300-plus dollars.

Host Amber Smith: So it's a lot for someone to consider, kind of pluses and minuses, whether they get it or not?

Katie Anderson, MD, PhD: And there are analogous, there are similar, discussions that happen for other travel vaccines -- for Japanese encephalitis, for rabies. These can also be expensive vaccines. But for certain scenarios, they may be very appropriate for a person to consider receiving, but not likely for everyone.

Host Amber Smith: Well, that makes sense. Thank you so much for making time for this interview, Dr. Anderson.

Katie Anderson, MD, PhD: Nice talking with you. Thank you.

Host Amber Smith: My guest has been Dr. Katie Anderson. She's the health commissioner for Onondaga County and a faculty member in microbiology and immunology at Upstate.

"The Informed Patient" is a podcast covering health, science and medicine, brought to you by Upstate Medical University in Syracuse, New York, and produced by Jim Howe.

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