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CDC Telebriefing on Investigation of Human Cases of H1N1 Flu

May 28, 2009, 1 pm ET

 

Operator: Good morning and thank you all for holding, your lines have been placed on a listen–only mode until the conclusion of today's conference. If you would like to ask a question, please press star one. I would like to remind all parties that today's conference is being recorded. If you have any objections, please disconnect at this time.  I would now like to turn the call over to Mr. Dave Daigle. Thank you, sir, you may begin.

Dave Daigle: Hi, this is Dave Daigle from CDC′s Media Relations. Today Dr. Anne Schuchat, our Director for the National Center for Immunization and Respiratory Diseases, will update us on the novel H1N1 influenza outbreak. She'll begin with a short statement and then take questions from the reporters. Thank you.

Anne Schuchat: Good afternoon everyone, I'm going to just briefly go through some case counts and I want to talk in more detail about three things today – what we've learned so far about the virus and some clinical warnings, our educational and prevention efforts that are ongoing and just a few words about vaccine development.

We do continue to see more cases in more places. Though we're not seeing dramatic large increases, the numbers I'll share with you today will look like a big bump from the last media briefing we've done. And that's really because of no reporting over the long weekend. Internationally, the WHO is reporting 13,398 confirmed cases in 48 countries, with Singapore and Bahrain being most recently added to the list. Here in the U.S. our official count today is 8,585 probable and confirmed cases. We're aware of 12 fatalities and 507 hospitalizations. Most of the people that are getting sick are continuing to be in that 5 to 24–year age group. That's 62 percent of all the cases that we're counting. And that it still appears relatively rare for people 65 and over to come down with this infection. There's only about 1 percent of our confirmed or probable cases in that age group. I want to let you know that beginning next week, we're going to shift to a different schedule. We'll be updating our case count information less frequently. And every Friday we'll be doing updates of what we call FluView, a more extensive report on many ways that we track influenza. Weekly reporting through FluView is what we do during the annual influenza season, including the peak of the season. And we hope that sharing information on that basis will keep people informed.

Next I want to talk a little about what we've learned about the virus so far. There are some respects in which this virus is behaving like the seasonal H1N1 influenza viruses. Remember that for seasonal influenza, we usually see H1N1, H3N2 and B strains of influenza. And when we look at this novel H1N1, there's some similarities between this and the seasonal H1N1. Seasonal H1N1 often causes more disease in younger people compared with the other strains that can be more common in older people. The seasonal H1N1 typically doesn't cause as many deaths as the H3N2 seasonal viruses do. In years when H3N2 predominates, we have a higher death toll than in years when the H1N1 predominates. So during the annual flu seasons, we've often found that H3N2 influenza viruses are most strongly associated with severe illness and more deaths. Back to the novel H1N1 virus, currently the attack rates that we're seeing, that's the percentage of contacts of an infected person who becomes ill, are fairly consistent with what we see with seasonal flu. In a typical influenza season, about 7 to 10 percent of the people in a community may become infected with an influenza virus. And about 20 percent of the people in households that have infected people contract influenza. And based on the studies that are ongoing, the field work and such, those ballpark figures are about what we're seeing so far in many of the communities where we're looking. Now, there's lots ongoing and the numbers can shift around a little bit. But those attack rates are secondary attack rates in the households and are in the right range for the seasonal flu studies that are reported from the literature.

But there are some aspects of what we're seeing that are very different from seasonal patterns. And of course, there's much that does remain of concern. This virus is circulating much later than the annual flu viruses. We're really not seeing much of any other seasonal flu viruses any more. But we are continuing to see this strain circulate, even though of course we're almost at June. This is a novel virus. And much of the population, we don't think, has immunity to it. So that's again different from the seasonal strain. The current seasonal flu vaccine that people got earlier this past year does not provide protection against the strain so far as we know. And of course, there are areas of the country, New York City and several other communities, where we believe active transmission and increased illness, including hospitalizations and deaths, are ongoing. So there are aspects where this is different from seasonal flu. And there's some aspects where the seasonal H1N1 looks a little bit similar to this novel H1N1. I want to stress again the idea of weather and local variation. So while we're regionally–– I'm sorry, nationally we're seeing influenza–like illness, the low, returning back downwards. There are areas where the influenza–like illness patterns are still increasing. The New York–New Jersey area is one of them. And in today's report, we see an increase in the influenza–like illness in region 10, which is Alaska, Idaho, Oregon and Washington. Now that regional data might obscure that a lot is going on in one or two communities, and not that much in the rest of the region. But in that region 10, we're seeing an uptick that we didn't see last week.

Next, I want to go through a little bit of information about some clinical observations. And you've heard us talking about the hospitalizations and the idea that the majority of hospitalizations that we're seeing are occurring in people who have underlying health conditions, pregnancy or various underlying medical problems. This is what we see in hospitalizations with seasonal flu. And so we are seeing that hospitalizations are more often occurring among people with these underlying conditions. When we look at our deaths, we have information on 11 of the 12 deaths that have been reported to us so far. And it appears that 10 of those fatalities occurred in people who had an underlying condition that put them at greater risk for severe complications of influenza. Some conditions like asthma can make it harder for a person to fight off an influenza infection. And we're seeing that kind of pattern that the more severe complications, hospitalizations or deaths, tend to be disproportionately in people with underlying conditions. Whereas the actual cases out there in the community are often in people with no underlying conditions at all. So we think these patterns suggest to us that it's important for people who have chronic health conditions, or people who are pregnant, to have special attention to warning signs to regarding when to seek care or receive medical treatment for a respiratory illness like influenza. These are the types of warning signs that we look, look to for regular respiratory infections. And they're certainly of concern for an influenza–like illness. And I'm just going to go through them. Because I don't think we've talked about them on one of these briefings before. In children, signs that need urgent medical attention include fast breathing or trouble breathing; blueish or gray skin color; not drinking enough fluids; severe, persistent vomiting; not waking up or not interacting; being so irritable that the child doesn't want to be held; and flu–like symptoms improve, but then return later with a fever and a worse cough. Those are warning signs we physicians think about all the time, with respiratory infections. And they're good to have in mind with this new influenza–like illness caused by the novel H1N1 strain. Just good things for parents to have in the back of their mind.

In adults, we look at another set of warning signs that suggest the need for urgent medical attention: difficulty breathing or shortness of breath; pain or pressure in the chest or abdomen; sudden dizziness, confusion, persistent or severe vomiting that doesn't go away; and flu–like symptoms that improve, but then come back again with a fever or worsening of cough. Underlying health conditions can bring on new challenges. And we know many people in the country have these conditions.  They can create the potential for more severe illness, that is not a certainty, but it's a possibility. And it's for that reason that we want to make sure that people who have these underlying conditions, or family members who care for such people, remain vigilant about these warning signs emerging. It's often best to consult or at least initially by phone or email, with a health care provider. That's probably a better strategy than going to an emergency room, but we do think that these warning signs can help people differentiate a cough or cold or respiratory symptoms without warning signs, from the type of signs that might lead you to want to attempt medical, to seek help from a medical provider.

I next want to turn to some comments about the education and prevention efforts that we have going on in partnership with state and local health departments and the health care professionals, as well as other parts of the U.S. government. From the outset, I think we've been very aggressive with our efforts to reach the public with information that can be useful as people try to protect their health and the health of their families and communities. As you know, we've developed and updated and issued a number of guidelines, interim guidelines for a number of concerns. And we've been stressing the importance of hand–washing, coughing and sneezing into tissues and staying home when people are ill. We've appreciated the help of the media in getting those messages out broadly to communities all over the country. Over the coming months, we plan to continue and expand our efforts to increase awareness of our recommendations and the symptoms associated with the H1N1 influenza. Some of our efforts will target everyone, others of these efforts will target people at higher risk for medical complications, and some of our efforts will target the traveling public, attempting to reach people who plan to be traveling to let them know how to protect themselves, as well as other people from this H1N1 virus. We're expecting that our efforts will use a wide array of media. We'll be working on radio and television, public service announcements, materials for distribution at clinics and health departments, posters in airports and other public places, new materials on our CDC website, and then continued use of social media, like the Twitter efforts that we've been making. So we appreciate the tremendous media attention that has helped us reach information–sharing around the world. We realize that the media isn't paying as minute–to–minute attention anymore, so we're taking on some other educational health promotion avenues that we hope will prepare people for the summer months and for the fall.

Lastly, I want to make a few more comments about the vaccine arena. Several days ago, CDC shipped candidate virus strains to several different manufacturers. Manufacturers involved in developing and producing the novel H1N1 vaccine, will start that process by producing candidate lots in the coming weeks. The strains that CDC has provided have been produced using both traditional methods, by growing the virus up in eggs, and new technologies, so–called reverse genetics. In addition to the U.S. manufacturers that we shipped the virus, the candidate virus strains out to, CDC will be providing candidate strains to manufacturers in other countries. And that will be happening in the coming days. We're pleased that we met the timelines we proposed for distributing the candidate virus strains, but I need everyone to remember that there is a lot that is unpredictable in making influenza vaccine for clinical test development or for large–scale production. We know every year with the seasonal influenza vaccine preparation, we all have to be prepared for some unpredictability. And although we have met this first initial milestone, we need to stay tuned over the next weeks and months because manufacturing and development and clinical studies can be unpredictable. At this point, I'd like to thank you for the interest you've had in this over the weeks. And go to the questions.

Dave Daigle: Thank you, Dr. Schuchat. Operator, first question, please?

Operator: Certainly, one moment. The first question is from Helen Branswell from the Canadian Press.

Helen Branswell: I was just wondering, I will ask the manufacturer, but I thought you would know, the reverse genetic seeds that you made, do you know if MedImmune is agreeing to waive its patent position for any vaccine that's made using a reverse genetic seed string?

Anne Schuchat: You know, I think that would be best asked to MedImmune directly.

Dave Daigle: Thank you, Helen. Next question, please, operator?

Operator: Our next question is from Tina Saey, from Science News magazine.

Tina Saey: I also have a question about the vaccine. Can you tell us a little bit about the testing that was done and when we are likely to see the first vaccine come off the production line? And who might be eligible to get this vaccine?

Anne Schuchat: You know, the steps going forward are that manufacturers will be developing lots of vaccines for use in clinical studies. And those clinical studies will be happening over the summer months. The ones that are coordinated here in the U.S. are really overseen by the FDA, working with manufacturers. And by the National Institutes of Health that runs a big clinical testing evaluation effort. So those two government agencies, FDA and NIH will be in the best position to update people on the studies going on this summer. The other steps that are going forward now are the development of ingredients for– what we call– bulk ingredients: bulk antigens and bulk adjuvant. So in addition to production of the actual vaccines that can go into people to be studied to determine things like what dose is needed to get an immune response, whether one or two injections will be needed to get a good persistent immune response, whether vaccination of different age groups gives different results, whether adjuvant is needed to give a good response or not. Those are the kinds of questions that clinical studies will do. At the same time, manufacturers will be producing larger amounts of bulk antigen and bulk adjuvant to be ready, should there be a request to actually produce a vaccine, to fill and finish a vaccine.

The actual making of the final vaccine doses that would go into people in a real program, need to wait for the clinical studies to be finished. Because you need to know how to make the vaccine, how much of each ingredient to put in it, and so forth. So there will be a lot going on in the summer, to study test lots of vaccine and look at their performance. As well as manufacturing of the ingredients that can be more rapidly assembled for use. There will be decisions later in the summer, or early fall, about whether to actually do that, fill finish step and how large–scale the production might be. And whether or not an immunization program here in the U.S. is going to be recommended for some or much of the population. So this first steps are very important ones. The handoff of the candidate virus strains to manufacturers so they can go do what they do very well. But we have a very long way to go before we are at the point of making decisions about vaccinations and potentially implementing them. If everything went really well in terms of the production, the testing, the answering all of those questions, and the manufacturing steps, and the decision to actually vaccinate was made, it would not be until the fall, when this kind of vaccine would become available. We're saying at this point, you know, not before October would you get doses that might be given to people, besides these clinical research settings. And so we will have a lot to think about over the months ahead. Planning to be ready to immunize should we need to, but also learning as much as we can about how easy it is to make a vaccine and about the circumstances in the southern hemisphere.

Dave Daigle: Thank you very much, Tina. Next question, please, operator?

Operator: Our next question is from David Brown from the Washington Post.

David Brown: Yes, thanks very much. Dr. Schuchat, you mentioned that there continues to be community spread in various places, New York, New Jersey, region 10 and other places despite the fact that it's a, increasingly inhospitable season. My question is, is it conceivable to you that there could be community spread in this continent and not community spread in Europe, which is roughly in terms of weather, and everything, the same, same season, same hemisphere. Does that make sense to you?

Anne Schuchat: Well I think there's, I would like to give two responses to that very good question. The virus properties in terms of its transmissibility and ability to survive in certain kinds of weather, is probably the same here as in Europe. But one thing that's different, I believe, in some of the European countries, is the point at which introduction occurred. I think that we had our first introductions quite a bit earlier than some of the European countries. And we also are likely to have had a bit more widespread disease by the time we were responding here in the U.S. And so it's conceivable to me that in a country in Europe where they really pounced on the first traveler who came back from elsewhere with this virus, with an aggressive containment strategy, they may have had a different experience. But I, I do agree with the idea that this appears to be a very transmissible virus. And that in our populations, with New York City as the poster child, it's being transmitted quite widely. So I think that with the right circumstances, with enough introductions of virus, it's hard for me to believe that the virus wouldn't spread easily, the way it seems to be doing here.

Dave Daigle: Thank you, David. Next question, please, operator?

Operator: Our next question is from Daniel DeNoon, from WebMD.

Dan DeNoon: Thank you very much for taking my question, Dr. Schuchat, my question is about the FluView information. During regular flu season I'm always a little frustrated by getting the results a week or even the Monday after the week, so that the information seems to be a couple of weeks old. Is there anything that's in the works to move this up a little more quickly? So far example on Friday we'll be getting the data through the 23rd of May. It still seems like a reporting what happened a week or so ago. Is there any way to get more updated data? And can you talk to me a little bit about how this is going to go out and when the FluViews will be available and what we should be making of that information that comes from a week before the period we're reporting it? Thank you.

Anne Schuchat: Sure. There are many aspects of our reporting during seasonal flu that were used during this active response period. And there's some aspects of our regular reporting that we enhanced substantially. So things like many of the reporting systems that would be weekly, we changed to daily. You know, the states were reporting to us every day. And the sentinel providers, who tell us about influenza–like illnesses were telling us what was going on every day. This was a huge, huge collaboration. And we're very grateful for the parts of the system that really stepped up for that. We are trying to gauge the intensity of reporting to the information needs. And some of the delay that happens is because we are testing isolates and trying to get results so between the time a person gets an illness, seeks care, gets a specimen, a specimen is forwarded to a state or public health lab, the specimen is typed there, which can happen right now. Or is typed here, which used to happen before the kits were sent out. You know, there's a natural delay there. We all wish we had data from everywhere available all the time. And I think this is one reason why I've been stressing how valuable the local health authorities are. You know, I think in New York City, people are getting information about what's going on in New York City in a very timely way, based on their active outreach to hospitals, and clinic sites and so forth. So I think, unfortunately here at the national level, as we try to put the story together from many communities, there are these lags. Some of our systems are more timely than others, and we are really looking hard at what are the information needs we're going to have when we go into the fall regular increase in seasonal flu with this new strain potentially on top of it. So, yes, you're right, that many of the data points you're looking at will have a delay built into them.

Dave Daigle: Thank you, Daniel. Next question, please, operator?

Operator: Thank you, our next question is from Richard Knox, from National Public Radio.

Richard Knox: Hi, thanks again for doing this. A couple of somewhat related questions. In the months ahead, if the swine flu virulence increases incrementally, as measured by deaths and hospitalizations, will we be able to pick that up, you think? I'm not talking about a sudden obvious surge in deaths, but something that may be more incremental. And secondly, what are the criteria under discussion that would come into play to trigger the decision to use the swine flu vaccine?

Anne Schuchat: Great, okay. The question of incremental changes in virulence severity is important. We are in planning stages with partners in other countries, with national, I'm sorry, international networks like the Pan–American Health Organization and World Health Organization, in ways to try to improve information availability from countries that will just be going into their flu season shortly or have already started. To understand whether the patterns that they see are different from what we have been seeing here. Severity has been extremely challenging to measure. because of the wide spectrum of illness that influenza can cause. And even with the most severe pandemic we know about, the 1918 pandemic, the mortality for that was about, at the 2 percent range. It's hard to be very precise in these ranges that we're seeing right now of.15 percent, or.2 percent of all cases resulting in death. So whether we'll be able to pick up an incremental increase in virulence, I can't promise. I think we think it's the kind of thing that's important to look for. And it's an emphasis area for us, but we may not be able to answer those information needs precisely.

There are a number of criteria that will be part of the decision–making, regarding use of vaccine in the fall. And I think one of the issues here is that I think many leaders are keen to get public input into these types of decisions, to understand where our communities and citizens are thinking. But in terms of the typical criteria, issues like how severe disease is, how disruptive disease is, who is getting the disease? Is it possible to prevent disease? You know, we certainly make a great effort to prevent seasonal influenza, with production of vaccine and use of more than 100 million doses of vaccine every year. So the opportunity we have right now, because this disease emerged in the spring here, for actual vaccine development to go forward, we have an opportunity to potentially have a prevention tool for something in the fall. That wouldn't have been the case, had disease first emerged in September or October. On the other hand, the, the clinical studies that will be done are going to be vital. Because if these clinical tests suggest in that we cannot make a vaccine that is protective, or is there is just unacceptable safety properties of a vaccine that appears to have a good immune response, we'll need to really weigh that heavily into a recommendation for vaccination. So there will be both practical criteria, like the results of these clinical studies, and information about the clinical disease we've had so far and disease that may be forthcoming in the southern hemisphere and where it occurs, and what age groups and what populations. Is it really feasible to prevent a lot of disease with a campaign. So those are some criteria that will go into that thinking.

Dave Daigle: Thank you, Dick. Next question, please, operator?

Operator: Our next question is from Denise Grady from The New York Times.

Denise Grady: Thank you. I'd like to ask you two things. One is if you could tell us something about when, where and how the clinical testing is done. And then the next question I'm wondering is in the southern hemisphere, is there any particular area, place within the southern hemisphere, where we generally look to make our judgments about what to expect? That's it, thanks.

Anne Schuchat: Sure. The question about the when, where and how of the vaccine studies, I'd like to refer you to BARDA for that. And then additionally, the National Institutes of Health will have a lot of information. BARDA is part of the Assistant Secretary for Preparedness and Response at the Department of Health and Human Services and they really have the lead in these vaccine questions for emergency types of vaccines like pandemic or prepandemic. And they will be coordinating some of these issues. The FDA, of course, regulates vaccines and is overseeing manufacturers' plans for studies. And companies may or may not share with us all the studies they're doing. But the FDA would be a good source of what's going on from their perspective, and then the NIH will be overseeing clinical trials carried on their vaccine testing and evaluation units, which their websites have lots of information about those vaccine evaluation units. That, but the specifics of the studies of which places will be doing what studies, I'm not sure of those decisions have already been made. But certainly one of those other organizations will be a better source than I am.

In terms of the southern hemisphere, what I'd like to say is that there is a– the World Health Organization oversees a global influenza surveillance network, that characterizes strains of influenza and every year is involved with the decision–making about the dominant strains that go into selection of, which strains will go into a vaccine for the northern hemisphere. And which strains will go into the vaccine for the southern hemisphere. And there are many investigators and influenza experts in the southern hemisphere involved in that process. One of the international collaborating centers under the WHO framework is in Australia. That's one of the four international collaborating centers. And they will certainly be influential in helping us understand what's going on with influenza strains in their country. We in the U.S. are one of the, at CDC, we have one of those four WHO collaborating centers. And we receive strains to test from that from many countries in the Americas, as well as other parts of the world. So there is an influenza network that really shares strains and information about strains all the time through the WHO framework. There are also a number of investigators in countries in the southern hemisphere and partnerships that the U.S. government has with a number of these countries. So we're at the stage of really needing to be ready for a disease to emerge or be a big problem in a number of places and need a flexible strategy where partners or we will be participating in evaluation efforts.  

Dave Daigle: Thank you, Denise, next question, please, operator?

Operator: Our next question is from Betsy McKay from the Wall Street Journal.

Betsy McKay: Hi, thanks very much, Dr. Schuchat. A couple of questions. One may be one of the million–dollar questions. But I'm just wondering, given what you know, are you able to give any predictions about the spread of this virus in the southern hemisphere? Is there any reason to believe it wouldn't spread widely as it has in Mexico and the U.S.? And the second question I had was just to clarify. I'm interested in the attack rates that you mentioned and I'm wondering if we have, if the population has less immunity to this particular virus, how can the attack rates be similar to seasonal flu? Which we presumably have more immunity? Or is that something that you've already factored in? Thanks.

Anne Schuchat: Yeah. The prediction question I wish I could answer that question. It would be a lot simpler if I could answer that question, because our planning could go forth with a much greater certainty. At this point, we really need to plan for multiple contingencies, for severe disease in the southern hemisphere, for no disease in the southern hemisphere, and for something in between. So I really don't know what's going to happen. Certainly, from what I've been seeing here in the U.S., the virus can spread easily and cause disease in people. So it would surprise me if we didn't see it anywhere in the southern hemisphere. But whether we see it in the sustained transmission, hospitalizations and deaths and so forth that we've heard reported from Mexico or that we've been experiencing, I just don't know.

In terms of–– second question? The attack rate, thank you. The attack rate information we have so far is partial. Some of the attack rate that we have hasn't yet been adjusted for whether family members were on anti–viral medicines, which of course would likely lower the attack rate. But the range we're seeing is pretty similar to what we see in seasonal influenza, with a higher attack rate in younger kids than adults in terms of the households that have been looked at. I think that in, in terms of attack rates, even with pandemics, attack rates don't get to be 100 percent, really, symptomatic attack rates are lower than that. We haven't yet measured asymptomatic infection in terms of serologic conversion or antibody, production of the antibody in people that are exposed to the virus. So it's possible that with additional testing and studies, these attack rates will be adjusted upwards, from what we've seen, once we understand who is exposed and infected, but not ill– what we call the asymptomatic attack rate. So I think it's too soon for us to say that, to say too much about the attack rates although we did want to share what we had learned so far.

Dave Daigle: Thank you, Betsy. Next question, please, operator?

Operator: Thank you. Our next question is from Mike Stobbe from Associated Press.

Mike Stobbe: Hi, thanks for taking the question. Actually two. First one tailing on to Betsy's–– could you remind us what were the attack rates for the pandemics in 1918, 1957, and the one in the late '60s? And my second question had to do with probably Southern England Journal of Medicine released two perspective pieces online yesterday. A group of three Columbia researchers, if I understand it correctly, ended by saying that the immediate ancestors of the novel swine flu virus have been around unnoticed for about two decades. Could you help me understand, is that consistent with what you all at the CDC have been saying? Or is that a little different?

Anne Schuchat: The, let me say something about attack rates and the pandemics of the past. When we did our pandemic preparedness planning, we had certain assumptions about attack rates that were on the range of 30 percent or so. But what's important to say is that the pandemic, the big difference in a pandemic is less the attack rate than the, in our planning assumptions, was the severity. That you know, quite a few people get influenza, even with seasonal influenza. But that expected deaths would be quite different in the 1918 scenario, versus a 1957 or '68 scenario. So some of our assumptions were that a lot of people would get sick, but what would be the proportion that needed medical care, hospitalization, or that might die. We are right now seeing this sort of 7 percent to 10 percent range of community attack rates, which is lower than that pandemic 30 percent, you know, situation. But of course, there are reports that there are some places, in Mexico for instance, that did have a pretty high attack rate, as the virus passed through the community. And remember in some of these places that we're measuring things, it's not over, there are still cases. So these would be snapshots in time. The second question that you asked was not about attack rates.

Dave Daigle: It was the New England Journal of Medicine.

Anne Schuchat: You know, I actually haven't read that yet, so I'm not going to be able to comment, I'm sorry.

Dave Daigle: Thank you, Mike. Operator, we have time for one more question.

Operator: Thank you. Our final question is from Helen Branswell from the Canadian Press.

Helen Branswell: Thank you very much for taking a second question from me. I was wondering, Dr. Schuchat, if you could tell me, you described at the beginning that this virus seems to be behaving in many ways like the seasonal H1N1 virus. And I'm wondering if the scientists at the CDC are debating, giving any additional thought to whether or not this is more like antigenic drift, that this is not perhaps a pandemic virus?

Anne Schuchat: You know, I don't think people are thinking that yet, but I think what is striking people is that you know, H1N1 years, of seasonal H1N1 years, seem to be, or years where there's who disease in kids than we see in the H3N2 years. That the elderly don't have as much disease when there's H1N1–dominant years. So you know it is quite similar in that way. In terms of the–– you know, the novelty of this virus, people are pretty convinced it's quite novel for humans. There is this issue with whether adults over a certain age have preexisting immunity, which would get to similarity with strains that were seeing quite a long time ago. But I think that you know, at this point, the genetics of the virus are very different from the things that circulate. The immune properties of course are questioned, because of this possible preexisting immunity in adults, in older adults.

Dave Daigle: Thank you, Helen. And operator, this concludes our briefing. Thanks to all for joining us.

Operator: Thank you and this concludes today's conference, you may disconnect at this time.

END

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