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Media Relations

Centers for Disease Control and Prevention


February 22, 2008


CURTIS ALLEN: Thank you. And thank you for your patience on the phone. My name is Curtis Allen.

We have with us today Dr. Nancy Cox. Dr. Cox is the director of the Influenza Division at CDC.

With that, I will turn that over to Dr. Cox. And thank you very much.

NANCY COX: Yes, good afternoon, everyone.

I know that there's been a lot of media interest concerning the vaccine strain selection for the vaccine that will be used next year that is for the 2008-2009 influenza season.

I think the interesting things are, in a nutshell, that the WHO and FDA VRBPAC have recommended that all three strains in the influenza vaccine be changed compared to this year's influenza vaccine.

Now, this sounds like a major change, because this really hasn't occurred before. But I wanted to clarify one point. And that is that, since 1999, we have been, within the WHO system, undertaking two vaccine recommendation sessions each year.

One occurs in September, and that is for the Southern Hemisphere vaccine recommendation. The second consultation occurs in February, and that is for the Northern Hemisphere vaccine for the following season.

If you look back to what happened in September, you'll see that two of three strains in the vaccine that was recommended for the Northern Hemisphere, two of the strains were changed. That means that vaccine manufacturers have actually had an opportunity to obtain the strains that were used for the Southern Hemisphere production and to work with those strains.

So they're not starting with a totally clean slate, that is to say, they've already had two of the strains that they've been able to work with so far.

So I think with that, with those remarks, I'll close and open the line for questions.

QUESTION: Hi. Thanks, Dr. Cox. Can you talk about what the companies are going to have to do? And can you tell us about how closely the strains are going to match? Because I understand that in the United States there wasn't as much of a mismatch as there was in Europe.

COX: You mean for this season, a mismatch for this season? I think that there really are very few data available about vaccine effectiveness, which is really the best measure of mismatch or suboptimal match.

I think that there are two separate questions. One, what is the mismatch or is there a mismatch for this year? And the second question is what do we predict for next year, in terms of this updated vaccine? And will it match the strains that are circulating next year?

So for the first question, we would say, based on our laboratory data, that the match is not optimal, both for the H3N2 component of the vaccine -- that's one of the influenza A components -- and also for the influenza B component.

In Europe, they've primarily had influenza A H1N1. And the data generated in Europe indicated that the strains that were circulating there were not so well matched with the vaccine strain, while the strain circulating in the United States, the H1N1s, were well matched to the vaccine. So there is some variation from country to country and from continent to continent.

With respect to next year's vaccine, it's impossible to predict -- because influenza is inherently unpredictable -- how well matched the vaccine strains are.

However, I would like to point out, for those of you who were either present at the FDA's VRBPAC meeting last year or who have read the transcripts that we, at that time, were concerned about the H3N2 component and the possible need to update it at that time.

Unfortunately, we did not have a viable egg isolate that could be used by the manufacturers. And so it was necessary to continue to use the Wisconsin/67 virus in the vaccine.

QUESTION: Hi, Dr. Cox. Could you just comment on any changes in the distribution of flu cases this season or whether any additional deaths have occurred?

COX: What we know is that the influenza season actually started out as being primarily an H1N1 year. So H1N1 viruses dominated through December into the first part of January, when we had a switch to H3N2 viruses. And if we look at the viruses overall, about 83 percent are influenza A, and at the current time, 63 percent are H2N2, so of the influenza A viruses, 63 percent are H3N2 and 37 percent are H1N1 and less than 16 percent are influenza B.

So we've really had a transition from what was predominantly a fairly mild influenza season with H1N1 viruses and B circulating and H3N2 to a lesser extent to a situation where H3N2 viruses are predominating overall.

ALLEN: You also had a question about the number of deaths, childhood deaths?

COX: Yes, in terms of the number of deaths, we do have a system that notifies us of deaths among children from laboratory-confirmed influenza. And now 22 deaths have officially been reported to CDC for this current season. Twenty-one of these deaths occurred between December 24th and February 10th, and so this is what we're reporting this week is an increase of 12 over the number of deaths, pediatric deaths, reported last week.

ALLEN: Thank you. Next question, please.

OPERATOR: Thank you. Our next question is from Helen Branswell of "Canadian Press."

Your line is open.

HELEN BRANSWELL, "THE CANADIAN PRESS": Hi, thanks very much for taking my question.

Dr. Cox, I was wondering if you could tell us -- there have been reports out of Indonesia that the health minister there is saying that that country is going to, or has sent some virus -- excuse me, specimens -- to your lab for risk assessment. There are reports of 12. And I'm wondering if you cold tell us if this is correct, if you've received them, or where they are and how many -- 12 specimens, how many people do those cover?

COX: Okay, so just to recap the situation very briefly, on February 20th, the Indonesian Ministry of Health contacted CDC and indicated to us that they would like to resume sharing avian influenza H5N1 samples that were obtained from human cases there. And on February 22nd, Indonesia did ship to CDC 15 samples that were obtained from two human cases that had confirmed H5N1 infections.

These were human cases that had been reported to WHO on February 5th and February 12th, and you can find information on the WHO Web site.

Now, based on our past experience, we would expect that these samples would arrive at CDC either over the weekend or possibly early next week, depending on a number of factors. And then we expect to obtain results from the samples over the next two weeks. And our first step will be try to obtain virus isolates from the patient sample and we'll be trying to determine if these viruses are the same as or different from the viruses that were sent previously.

So we'll be doing a number of laboratory tests to make these determinations.

ALLEN: Thank you. Next question.

OPERATOR: Our next question is from Sabrina Gibbons of WSB Radio.

You may go ahead.

SABRINA GIBBONS, WSB RADIO: Hi, Dr. Cox. I have a question about the vaccine and it being available in time for next flu season, since we're having to overhaul the vaccine, although you did say that there were two strains that you already have available.

So what do you see for that?

COX: I think there are a number of elements within vaccine production that make the situation a little unpredictable, but I think that because the vaccine manufacturers have had some experience with two of the strains already, and there are some reagents available in the Southern Hemisphere for vaccine potency testing, things could go more smoothly than one would first think when you realize that there's a complete overhaul of the vaccine.

So, in other words, because of the Southern Hemisphere strain recommendations, we have a jump start on the situation. But, as we all know, one of the rate-limiting factors for getting the vaccine actually formulated and tested and out of the door is how well the virus strains grow. And, of course, when you change strains, the growth properties of the new strains are unpredictable. Some strains inherently grow better than others.

And so one of the determinants of whether the vaccine is available as early as it was this year will be how well the strains grow.

MODERATOR: Next question.

OPERATOR: Thank you. Bob Roos from CIDRAP News, you may ask your question.

BOB ROOS, CIDRAP NEWS: Yes, thank you. Actually, I just had the same question about two of the possible effects on the timeline and production of the vaccine, so you've already addressed it. Thanks.

MODERATOR: Thank you, Bob.

Next question, please.

OPERATOR: Thank you. Our next question is from Karen Shideler from "Wichita Eagle."

You may ask your question.

KAREN SHIDELER, "WICHITA EAGLE": Dr. Cox, you gave us an update on the pediatric deaths of the past week. I'm wondering if you could give us a general update on the influenza season in general over the United States in the past week.

COX: Sure. First of all, in brief, seasonal influenza activity has increased during the past week. And I've already mentioned that H3N2 viruses are predominating in the United States. And then I think the new information really is that during this week, 49 states have reported widespread activity. And this is up from 44 states last week and one state reported regional influenza activity.

And we've also seen that the percent of specimens that were tested by the U.S. World Health Organization and National Respiratory and Enteric Virus Surveillance System collaborating labs is about the same as last week.

Last week, it was 33.3 percent, and this week it's 34 percent. So it looks like it may be leveling off a bit, but it's difficult it know.

Our index of influenza-like illness increased in six of the nine regions compared to last week and actually was above the region-specific baselines in all of our nine regions.

So I think that what we can say is that influenza activity has continued to increase, but not quite as dramatically as the increases that we had seen over the previous two weeks.

QUESTION: Hi, thank you for taking my call. Part of my question was going to be an update on the pediatric deaths, so you sort of got to that. But could you elaborate on whether the deaths in children were cases of the H3N2? Or do you know which strain was involved there?

COX: We don't have complete information on the influenza type and subtype associated with these deaths. And so we really can't -- we just have fragmentary information at the moment.

QUESTION: Thank you. Dr. Cox, I have two quick questions about next year's vaccine. And the first one is: Which is the strain that manufacturers have no experience with? And number two: Why did the WHO decide to change the H1N1 strain next year?

COX: OK, the strain that the vaccine manufacturers in the Southern Hemisphere did not have experience with during their production season is, in fact, the H1N1 strain. It was updated from the Solomon Islands-like virus to a Brisbane/59/2007-like virus.

The reason that it was updated is that it was very clear that there is an increasing proportion of H1N1 viruses that were not well inhibited by antibody -- and we do these tests in the laboratory -- but by antibodies made against the vaccine strain.

In addition -- and those were antibodies in our animal model, which is ferrets -- but in addition, when we actually used the serum from vaccinated individuals who had been given this year's vaccine and tested the serum for antibodies to the vaccine strain itself and to some currently circulating viruses, we saw that the currently circulating viruses were not as well covered by the antibody.

So putting all of these pieces of information together and seeing that H1N1 viruses have circulated widely in a variety of different countries in the world and had caused outbreaks, and the viruses were changing, and the vaccine-induced antibodies weren't covering the current strains as well, WHO took all this information together and made a recommendation to update the vaccine.

The same data were presented to FDA's VRBPAC yesterday, and that advisory committee agreed with the WHO's decision to update the H1N1 component.

QUESTION: You know, my question was actually already answered. Thank you.

QUESTION: Yes, hi, Doctor. Thanks. I just wonder if you could put this into historical context. It looks like everything's kind of within the historical norms on your Web site there, but I want to get to the out-patient illness surveillance.

It looks like the influenza-like illness spikes to way above where it's been in previous years. And if you could just help us put this into historical context, is this a normal year, or is this much higher than it has been in the past?

COX: That's a question that's been asked by a number of individuals, and I think it's an important question. You'll have to recall that, when you look at our surveillance data that we post on the Web site, we're only showing the last three years of influenza activity.

And so if we step back from looking at just three years of data to looking at the 10 year perspective, what you would see is that we really are within the normal parameters of what we would expect for an influenza season.

So that very rapid increase that you see in the percentage of visits for ILI that are reported by our sentinel providers is quite dramatic, but it's really within the parameters that we have seen in the past when influenza season really takes off, as it has this year.

QUESTION: Hi, Dr. Cox. Thanks for taking our questions. I was just wondering if you all had seen any clinical implications of the vaccine mismatch, whether it be patients with the flu who've been vaccinated this year or pockets of Tamiflu resistance? Thanks.

COX: OK, thank you very much. We actually often receive anecdotal reports of people who have received vaccines and who have confirmed influenza.

And, of course, we know that the influenza vaccine is not perfect, even when it's optimally matched. In young, healthy adults, we expect vaccine effectiveness to be 70 percent to 90 percent.

But we actually have ongoing studies to determine vaccine effectiveness in a very timely manner. We should have data that are strain-specific for the influenza A viruses. And once we have those data available, they will be published in the MMWR.

So, in short, we're really looking at vaccine effectiveness. And we'll be able to report it by type and subtype, specifically for the influenza A subtypes, because we have more cases of H1 and H3 than influenza B. And those data should be available within the next two to three weeks.

With respect to pockets of activity associated with antiviral-resistant viruses, we've actually seen antiviral resistance only sporadically in now eight states. So there really are not pockets of resistant viruses, as far as we can tell at the moment.

We are increasing our surveillance for antiviral resistance. We've solicited a lot of samples from the state health departments, and we expect to have a great deal of additional data over the coming weeks.

QUESTION: Hi, I'm sorry if I'm repeating any territory here. My question was about activity. And I see on the Web site it says 49 states now see widespread activity. Is that the case?

COX: That's correct.

QUESTION: And I heard you say something, and I kind of missed all of it. Were you saying that it looks like the activity is slowing down?

COX: Actually, what I said is that it looks like the increase that we saw between last week and this week was not as dramatic as the incremental increases that we saw during the previous two weeks.

So it's hard to say. We really can't predict the severity or the duration of influenza season. But looking at the data, it does suggest that we may be nearing the peak within the next few weeks.

ALLEN: OK, thank you for being with us today, the CDC's influenza update.

And the Flu View should be up on the Web site soon. But just to review, there are 49 states reporting widespread activity. This is up from 44 states last week. One state -- that is Florida -- is reporting regional influenza activity.

You will be able to find this information at

Thank you very much.


Content Source: Office of Enterprise Communication
Page last modified: February 22, 2008