Press Briefing Transcript
CDC Update: Flu Season and Vaccine Effectiveness
Friday, January 11, 2013 at 11:30 a.m. ET
OPERATOR: Please stand by today for today's call. It will begin momentarily. Please stand by. Thank you. Welcome. Thank you for standing by. At this time, all participants are in the listen only mode. You may press star one to ask a question. Today's conference is being recorded. At this time I’ll turn it over to Mr. Tom Skinner. You may begin, sir.
TOM SKINNER: Thank you, Shirley. Thank you all for joining us today for this update on flu activity in the U.S. as well as some information on an MMWR that we have put out on vaccine effectiveness. With us today is the director of the CDC, Dr. Tom Frieden, as well as a Medical Epidemiologist from our Influenza Division, Dr. Joe Bresee. Dr. Frieden is going to give some opening remarks of maybe five to seven minutes in length and then we'll get to your questions. Dr. Frieden may have to drop off the call at some point during the Q&A and then we'll have Dr. Bresee to stand by and answer additional questions. With that: Dr. Frieden.
TOM FRIEDEN: Thank you very much for joining us. Today, what I’d like to do is give an update on what's going on with flu. I know that there's a great deal of interest in how this year's flu season is unfolding. And as we always do at CDC we want to give you information as we get it so that we can put the appropriate perspective on this year's flu season. The bottom line -- it's flu season. Most of the country is seeing or has seen a lot of flu and this may continue for a number of weeks. There are three things that I want to cover this morning. First: an update on the level of activity. Second: an overview of data that we're releasing about the effectiveness of this year's flu vaccine. And third: steps that everyone can take to protect themselves. I'll also invite Dr. Joseph Breese to join me in answering your questions. So as we said in early December, the season got off to an earlier start than usual; about a month or so ahead of what we normally see.
We're continuing to see influenza activity remaining elevated in most of the U.S. It may be decreasing in some areas but that's hard to predict because particularly when you have data from over the holiday season, trends may be a little hard to predict. Declines may be because the disease level has peaked in some areas and is coming down. Or next week we may see that go up again. But we are seeing a decrease in the most recent week in some areas while other parts of the country, particularly in the west, appear to continue to be on the upswing since they experienced the flu this season more recently later in the season. This really is not surprising. Influenza activity ebbs and flows during flu season and tends to spread across the country. It also has some variability even within states and communities. So just because it's widespread in one city or state doesn't mean it will be throughout that area. The -- as you know, with the past eight years or so, we have monitored, recognized child or pediatric deaths from influenza. There are two more influenza associated pediatric deaths reported in the past week. That brings the total to 20 deaths this season.
We also look at outpatient monitoring or surveillance for influenza-like illness and that fell in this week to 4.3 percent from 6 percent. That's above the baseline of 2 percent, but down from last week. And again, that's the trend which really only the next week or two will show whether we have in fact crossed the peak or whether we'll see a resumption of the increase in the next week or two. Because of the holiday season, again, trends are harder to predict. Twenty-four states and New York City are now reporting a high level of influenza-like illness activity. That's a decrease -- that's down from 29 states before -- and 16 are reporting moderate levels of ILI activity, up from nine. A third -- exactly 33 percent of strains -- were positive for influenza. That's down. And in terms of the pneumonia and influenza mortality, the proportion of deaths attributed to pneumonia and influenza rose to slightly above the threshold for the first time this season. We usually see a several-week lag from the time that illness starts to rise to the time that the deaths start to rise. So this is in line with what we would expect. Forty-seven states report widespread geographic influenza activity, that’s up from 41 last week. Nationally, it’s likely that influenza will continue for several more weeks. During the past decades, we have seen an average of about 12 consecutive weeks, three months of the ILI being elevated. But as we often say, the only thing predictable about flu is that it's unpredictable. Only time will tell us how long our season will last and how moderate or how severe this season will be in the end. That's the update on our activity. I'll go through vaccine effectiveness and steps people can take to protect themselves and then we'll take questions.
Each year since 2004 and 2005, CDC has estimated the effectiveness of this seasonal influenza vaccine. We look at how likely that vaccine is to keep you out of a doctor's office. We have also looked at how likely it is to prevent people from being hospitalized or---to dying from the flu and those numbers tend to be similar or perhaps a little more effective at preventing hospitalization or death. With the early onset of this year's flu season we can provide earlier information on our best estimate of vaccine effectiveness. We looked at 1,155 children and adults in flu effectiveness network program. These are people who were seen between December 3rd of last year and January 2nd of this year. And that allowed us to evaluate or estimate the overall effectiveness of the vaccine. Once we looked at the differences across study sites and correct for that but not other factors, we found the overall vaccine effectiveness to be 62 percent. That means that if you got vaccinated you’re about 60 percent less likely to get the flu that requires you to go to your doctor. So what we have known for a long time is that the flu vaccine is far from perfect. But it's still by far the best tool we have to prevent the flu. Now, there are differences in different groups. In the past we've found for example that younger people tend to be better protected by the vaccine than older people. That the people who have underlying illness may be less likely to be protected. So those differences have not yet been fully assessed. This is an early estimate, but as I said at the outset our basic approach at CDC is to get information as quickly as we can and then share it openly and transparently.
Finally, there is a lot that you can do to protect yourself against the flu. Vaccination is the single most important step you can take to protect yourself. Again, vaccination is far from perfect, but it's by far the best tool we have to prevent influenza. You can still protect yourself through vaccination. We're hearing of spot shortages of the vaccine so if you haven't been vaccinated and want to be, better late than never, but call your provider ahead of time you may have to check in several places to find the vaccine because most of them, more than 130 million doses that were produced by the vaccine manufacturers this year have already been given. Second, be sure to cover your cough and sneeze and stay home if you're sick with cough and fever. Keep your children home from school if they're sick with cough and fever. This really does help prevent the spread of flu. Washing your hands often is important. It can reduce illness from flu and other things. And if you get sick with flu-like illness, if you have fever and cough, if you're very ill or if you have an underlying condition, it's very important that you contact your doctor because early treatment with antivirals such as Tamiflu can reduce severity of illness can keep you out of the hospital or prevent even more serious illness. There's as always more information available at flu.gov or CDC.gov. Thanks again for joining us and Dr. Bresee and I will be available to answer your questions.
TOM SKINNER: Shirley, I think we're ready for questions please.
OPERATOR: Thank you. At this time we’re ready to begin the question and answer session. If you would like to ask a question, please press star one. Please unmute your line and record your name clearly. To withdraw your request, press star two. Again press star 1 to ask a question, and one moment for our first question. Our first question comes from Miriam Falco with CNN Medical News Atlanta. You may ask your question.
MIRIAM FALCO: Good morning, Dr. Frieden, Dr. Bresee. So we're now up to 47 states with widespread flu activity. Can you tell me what the threshold is for that and also in which areas we're still seeing -- you mentioned the west, but little more specificity with where we're seeing things possibly getting a little better and where we’re seeing things possibly still getting bad? What are the bad spots right now?
TOM FRIEDEN: Dr. Bresee?
JOSEPH BRESEE: Sure, happy to. So, widespread activity is a definition that we use and it describes how many geographic areas in a state—within a state are affected by flu. So widespread means that more than 50 percent of a geographic sub region in a state – like counties for instance -- are experiencing flu. What we're seeing right now is that there's more widespread states than there were last week, but there's probably fewer states this week that are reporting high levels of ILI. So gives us hope at least that some of the states are starting to get to the peak or a little past peak, especially in the southeastern part of the United States where the earliest disease was seen during the year.
MIRIAM FALCO: But where is it getting still bad?
JOSEPH BRESEE: Well –There's flu all over the country right now. If you look at the map there's widespread disease in most states and high levels of disease in most states. I think the only area of the country that's still relatively unaffected, though they still have lots of flu themselves, is the far west coast. The rest of the country has lots of flu.
TOM SKINNER: Next question, Shirley.
OPERATOR: Thank you. Our next question comes from Mike Stobbe with the Associated Press. You may ask your question.
MIKE STOBBE: Good morning. Thanks to you all for taking the question. Two, actually. One, Dr. Frieden I think mentioned there might be some spot shortages of vaccine. I was wondering in what parts of the country you have heard reports that there are spot shortages? And the second question, if you can clarify for me something you were saying about the ILI map and how the holidays may have -- may have -- I don't know, messed up our understanding of what's going on. It would seem like the holiday week would have more doctor's offices closed and that would have diminished the number -- I'm not quite clear on how that might skew our current understanding of the ILI map.
TOM FRIEDEN: I'll start and ask Dr. Bresee to continue. Because ILI looks at the proportion of office visits that are for an influenza-like illness and because people often don't go to the doctor's office for routine check-ups during the holiday season, so the number of visits may be down, you can see just unpredictable changes in the proportion of ILI in doctor visits. Generally over a holiday season, people who come in and tend to have a different pattern of illness and perhaps be -- have a higher – a larger proportion of serious illness than those who don't. Dr. Bresee?
JOSEPH BRESEE: That’s exactly right. I would say the same. I think, Mike, if you look back at the previous years you do see these little rises and notches around the same weeks in previous years. The same—the question about vaccination I think that we don't have specific data about where vaccine is and who has which vaccine. I guess the message is that a lot of the vaccine in the United States -- the United States – when we recommend it be given— and so by this time of the year by a lot of the doctor's offices – and so it may be that you have to call a couple places to find the vaccine when you go out, but it should be available for you. [Editor’s note: This statement may be incomplete due to audio interference.]
MIKE STOBBE: Thank you.
TOM SKINNER: Next question, Shirley.
OPERATOR: Thank you. This question comes from Jonathan Serrie with Fox News. You may ask your question.
JONATHAN SERRIE: Good afternoon, gentlemen thanks for taking my question. If you could explain the vaccine effectiveness of 62 percent, help me to understand does that mean a 62 percent chance you will not get the flu if you're exposed to the flu or how do you come up with that figure?
TOM FRIEDEN: Basically, that says that if you've gotten the flu vaccine, you're 62 percent less likely to need to go to your doctor to get treated for flu.
JONATHAN SERRIE: Thank you.
TOM SKINNER: Next question, Shirley.
OPERATOR: Thank you. This question comes from Deborah Cox with Boston Globe, you may ask your question.
DEBORAH COX: Hi, there, thank you very much for taking my question. I was wondering about the -- looking at that vaccine effectiveness numbers and wanted to break it down a little bit, which you guys did in your report, where you say that it's 55 percent effective against influenza A versus 70 percent effective against influenza B. And certainly here in Massachusetts, most of the flu that's circulating is the influenza A strain which we’ve talked about tends to be more severe comes with more complications and just wondering if the CDC is concerned at about the fact that -- if the vaccine, this particular one this year at least seems to be far less effective against influenza A than B and whether if there's any drive to kind of create a better vaccine.
TOM FRIEDEN: A couple of comments and then Dr. Bresee may want to add. First, the numbers are relatively small, this is preliminary information and the confidence intervals for those two strain-specific estimates overlap. So the data that's presented is not enough to say that there is a real difference in the effectiveness against the two different strains. But yes, we definitely are working hard, as is NIH as are the vaccine manufacturers to try to come up with a better vaccine. Childhood vaccines routinely get well over 90 percent vaccine efficacy. And that's what we'd like to see. Many of the vaccines last longer than a year and cover a wider variety of the subtypes of an organism. So, the flu vaccine is far from perfect. That's why you have to get revaccinated each year. That's why we have to reformulate the vaccine each year. So we wish we had a vaccine that was long-lasting and universal against flu, but that's a ways off and today, still the flu vaccine is by far the best prevention we have. Dr. Bresee, do you want to mention anything more about the strains?
JOSEPH BRESEE: Nothing to add. I think that was exactly the explanation I was going to give. Perfect.
DEBORAH COX: Can I ask a quick follow-up? You say it's a little less effective in people who have underlying conditions. Can you name a few of those conditions?
THOMAS FRIEDEN: That would include frail, elderly, people who may have had cancer, chemotherapy, people who may have immune systems that are weakened or be on medications that would weaken their immune system, including people who are on long-term oral steroid treatments for conditions that require that. So, it's kind of the opposite of what we'd wish. The people who are most susceptible to severe influenza are also less likely to get the benefit that others get from the vaccine. Again, Dr. Bresee, anything to add?
JOSEPH BRESEE: No, not a bit. I think that's exactly right. And I would say that because -- because these groups do have very high rates of complications and severe diseases, like the elderly and young children or people with immune-compromising conditions although the vaccine may work less well in some of those people it's clearly the best tool to give. And the disease burden in those groups are so substantial that even a modest effect compared to a young, healthy person is of tremendous public health importance.
TOM SKINNER: Next question, Shirley.
OPERATOR: Thank you. Next question comes from Alice Park with TIME magazine. You may ask your question.
ALICE PARK: Yes, good morning. Wanted to address the 62 percent effectiveness number. Can you give us some perspective as to how this compares to other years and it seems like it's very close to that sort of just threshold of being barely sort of how you define effective. And second question relates to the kind of pattern we're seeing with the cases with so many cases, a volume of cases of -- and coming on so quickly, does that raise any concerns about the virus sort of being more likely to mutate and, you know, given this relatively low effectiveness rate kind of mutate out of -- you know, to be clinically resistant to the vaccine and cause more problems further down the road?
TOM FRIEDEN: No, we don't expect to see any changes in the flu vaccine during the season. We'll have to track the patterns around the world to see what's most likely to happen in the next flu season. And, you know, you can say 62 percent is certainly far less than we wish it would be. But it's a glass 62 percent full or a 62 percent reduction in the number of people who would be going to doctor's offices if they hadn't been vaccinated. So it's certainly well worth the effort. I get vaccinated. My family gets vaccinated and we hope we'll be able in a few years to have a better vaccine. In terms of the trends, it does vary in terms of how well the vaccine is matched to the circulating strains. Sometimes we don't have a good match and the vaccine effectiveness can be quite low because we're vaccinating against strains that aren't circulating. Dr. Bresee, can you comment further about the historical perspective on vaccine effectiveness?
JOSEPH BRESEE: Yeah, sure. In fact, we would say that 62 percent effectiveness of the vaccine in a population that's a broad population that includes both healthy people and a lot of elderly and sick people is what we'd expect from influenza vaccine in a year in which the circulating strains look like the strains that were included in the vaccine. If you look back over the last few years at the studies that CDC has done, this is in line with what we found and also in line with some recent reviews of vaccine trials that have been done over the last several years. And so I think that the 62 percent we'd love it to be better, but we think it's -- it is actually a substantial public health benefit for the population.
TOM SKINNER: Next question, Shirley.
OPERATOR: Thank you. Next question comes from Stephanie Armour with Bloomberg News. You may ask your question.
STEPHANIE ARMOUR: Great, thanks very much. I have two questions for you. One I'm trying to get some information on all the deaths so far this year compared to the previous season. And my other question -- from influenza. My other question is when you talk about outpatient visits and the 4.3 percent above the national base line of 2.2 percent, can you explain what the national base line refers to?
THOMAS FRIEDEN: Dr. Bresee?
JOSEPH BRESEE: Sure. Happy to. First the deaths. We don't count -- except for pediatric deaths which we do count in our reportable diseases to the CDC-- we don't on a weekly basis during the season estimate the total number of deaths that occur in the population. We do have signals of the number of deaths like the 122 Cities Death system that you might be aware of. So it won't be until after the season that we'll have a feel for how many deaths occurred because of the influenza circulation in the winter. But we do run models on that and know that from year to year, it varies quite a bit. But really is in the thousands to tens of thousands of deaths each year. And so I can't answer it right now, but hopefully we'll be able to answer it in just a little while after the flu season.
The second question was -- oh, the base line. I apologize. The base line is a base line that's calculated from the last three years of data, prior to this year. Taking the low months from influenza-- say the summer months of influenza -- looking at the proportion of patients who come in during those months that have influenza-like illness compared to the total number of people that come to clinic. And then taking that and taking -- taking two standard deviations above that. And so basically what it's meant to represent is during the low season, what do we see? And if we elevate that, what line would we assume that the disease occurring above that line is attributable to influenza? And so what we're saying now that above threshold is, is that when those lines, when those dots get above the epidemic threshold either for the nation or for a region, we think that influenza disease has started and that tends to correlate quite well with influenza circulation in the community.
TOM SKINNER: Next question, please.
OPERATOR: Thank you. Next question comes from Erika Edwards with NBC News. You may ask your question.
ERIKA EDWARDS: Hey, there, I was wondering if you could talk more about the specific kinds of strains we're seeing and whether they're included in the vaccine. And specifically a reported fourth strain that popped up and may be not included in the vaccine?
TOM FRIEDEN: Sure. About 90 percent of all of the strains circulating are included in the vaccine. In fact, they're the most -- the three most common strains and the current vaccines have only three -- have space for only three strains. So the pick of vaccine strains was as good as it could have been this year. The other close to 10 percent are a second influenza B. And within a year or two, we do expect manufacturers to have on the market vaccines that have space for four different vaccines including two influenza B’s. So that's the explanation of that. Dr. Bresee, anything to add?
JOE BRESEE: No, sir. That's great.
ERIKA EDWARDS: If I could ask a quick follow-up, is there any evidence that that particular strain is more severe or less severe or about the same as the flu we're seeing?
TOM FRIEDEN: Dr. Bresee?
JOE BRESEE: No, there's not. The two B strains, I think the fourth strain you're talking about is the B that is of a genetic lineage that's not included in the vaccine. There's no evidence that that strain is more or less severe than the other strains.
TOM SKINNER: Next question, please.
OPERATOR: Next question comes from Maryhelen Campa from CBS Network News.
MARYHELEN CAMPA: Hi, thanks for taking my call. You mentioned that the area of the country that's relatively lower with the flu numbers is the far west. Can you talk a little bit more about that? Maybe provide some numbers? Is there anything that quantifies the spread west other than the usual?
TOM FRIEDEN: I will -- I’ll begin. Then, I'll turn it over to Dr. Bresee and then I have to sign off the call. The -- generally we do see flu essentially roll across the country as it rolls across the globe. So it's not unexpected to see it start in the south, southeast and then spread sporadically to the west. That would be a common pattern. Though again you can’t predict. Sometimes it skips areas of the country for reasons we don't understand. I do want to reiterate a couple of messages before I turn it over to Dr. Bresee because I do have to drop off the call now. We're in flu season. Most of the country has seen or is seeing a lot of flu. This may continue for a few more weeks. We don't yet know whether we are over the peak. It does appear that in some of the south and southeast we are seeing that we are past the peak and declines in cases. But only the next couple of weeks will make that trend clear. You can't really make a line with two points. You need multiple points to see where that line is going, particularly when you have the holiday season which can sometimes skew some of the data. The vaccine effectiveness is what we're releasing early this season because we have more flu earlier this season, so we're able to make the estimate. It's in line with what we expect. It shows that the flu vaccine can prevent most cases of flu, but it's far from perfect. It's still the best thing that you can do to protect yourself. There's still flu vaccine out there if you want to get vaccinated. Better late than never. But if you get flu-like symptoms and you're either very ill or you have underlying illness that may make you more susceptible to being very ill, then by all means see your doctor because treatment with antivirals especially in the first 48 hours after you have become ill can really help you avoid serious illness or hospitalization or even death. So, Dr. Bresee, if you could follow up with this question. Thanks to everyone for being involved and I'll have to drop off at this point.
JOE BRESEE: Thank you, Dr. Frieden. I'll just reiterate what Dr. Frieden just said which I think is important. The geographic spread of flu is unpredictable. Each year we see intense flu activity in some parts of the country, while other parts of the country have less flu. And it changes over time. And so the fact that the west coast is experiencing a little less flu than other parts of the country is not too surprising. And so I suspect that over the next couple of weeks the west coast will have more flu than they do now and some of the other areas will have less.
TOM SKINNER: Next question, Shirley?
OPERATOR: Thank you. Next question comes from Dan Childs from ABC News. You may ask your question.
DAN CHILDS: Hi, good afternoon. Thank you for taking my call. The question that I had was, you know, we're hearing about as you say spot shortages of flu vaccine around the country. Is there any suggestion that there might be a shortage of Tamiflu?
JOE BRESEE: It’s a good question. Thanks. There have been some issues with finding-- in some places, occasionally -- issues in finding the suspension, the pediatric formulation. That's a liquid. Those are spot shortages as well and the company is working hard along with FDA to remedy that. They have issued guidelines now and it's available in the FDA website -- and accessible through the CDC website -- guidelines for taking the 75 milligram tablets, which is the strength you give adults, and creating a pediatric formulation with that. I think there are some things we can do despite if you can't find the pediatric formulation, you can reconstitute it. Your pharmacist can reconstitute it from the adult-sized pills as well.
DAN CHILDS: Ok, fantastic. There's no shortage in the adult pills, it's just the pediatric liquid formation?
JOE BRESEE: That’s what we have heard, yes. I think the FDA is monitoring this closely and probably has the most recent data.
TOM SKINNER: Next question, Shirley.
OPERATOR: Next question comes from Robert Lowes from Medscape Medical News.
ROBERT LOWES: Thanks for taking my call. I don't want to beat a dead horse further, but I guess I want to at least clarify one point and then I have a follow-up question on something else. Most people in the country see a more harsh flu season. They learn that the vaccine effectiveness is only 62 percent and they would say, aha, we've -- if we had a better vaccine we wouldn't have such a severe season. What would you say to those people who would look at a so-so vaccine as explanation for why, for instance, we have the public health emergency in Boston? Second question, apparently, the pandemic virus is a very minor player in this year's season. What do you conclude from that?
JOE BRESEE: I’ll take the second question first, because I think it's an interesting question. We're not seeing much of the 2009 H1 virus yet so far this year, though it should be said that Europe and other places in the world are. And so that virus continues to circulate in the world. We know that influenza viruses in a given country, in a given city, in a given region will vary from year to year and in unpredictable ways. So I’d say we are seeing less of that virus now, but it doesn't mean we'll see less of it all during the season and it doesn't mean that it's gone from its vantage. For the other question I think that -- I would say that we all want a better vaccine. If we had to draw up a vaccine, we would design a vaccine with 100 percent effectiveness. If everyone got vaccinated with that vaccine, we'd certainly see less disease. That said, a vaccine against a disease like influenza which causes hundreds of thousands of hospitalizations and tens of thousands of deaths each year, that reduces the chance of you having one of those outcomes by 60, 50, 70 percent, we think is a substantial contribution to public health in the country. We'd love a better vaccine. This is by far the best tool we can get; that we have to prevent what we think is a substantial public health threat.
TOM SKINNER: Next question, Shirley.
OPERATOR: Thank you. Next question comes from Donald McNeil with The New York Times. You may ask your question.
DONALD MCNEIL: Thank you. I was hoping Tom Frieden would be here to handle this, but can you talk about the other viruses that are circulating? Lots of people are sick. Clearly not everybody has the flu this year. They have a whole constellation of symptoms, other things are going on. Can you just discuss that?
JOE BRESEE: Thanks for the question. This is Joe. I'll try to answer this question. We are seeing an early flu year as we talked about, but at this time of the year we also see lots of other respiratory viruses like respiratory syncytial virus, metapneumovirus, parainfluenza virus and those are circulating now too. We are seeing a norovirus, which causes vomiting and diarrhea. So I think a lot of the calls that we have gotten anecdotally and a lot of the news reports that talk about clinics being very busy and ERs being very busy may in part be due to a confluence of a lot of these winter-time viruses occurring at the same time in some communities.
DONALD NCNEILL: Thank you.
TOM SKINNER: Next question, please.
OPERATOR: Thank you. It comes from Elizabeth Weise from USA Today. You may ask your question.
ELIZABETH WEISE: Hi, thanks for taking my call. I had two questions. One that I believe -- I believe it was in the MMWR that about 37 percent of Americans had been immunized against the flu this year. Is that high or low? And then what could we be doing to create a more effective influenza vaccine? Are there things that we should be looking towards that perhaps Europe’s doing that we're not?
JOE BRESEE: Yeah, thanks for the question. Yeah, you're right. The last look for the vaccine coverage surveys we did showed that about 37 percent of Americans had been vaccinated by mid-November. That's about on track with what we saw last year at that time. We have seen a lot of vaccination happening in the last couple of weeks, so I don't know where we'll end up this year. But hopefully we'll end up much higher than 37 percent and close to 50 percent. We would like, of course, that every American gets vaccinated that's eligible for vaccination for flu. The fact we're seeing as good vaccine coverage as last year, and by historical standards, very good vaccine coverage in the last couple of years, we'd like it to be much higher because still around half of the Americans don't get vaccinated for the flu each year and we think that's too many.
The second question, how do you make better vaccines and are other people making better vaccines than we are? That's a good question too. We’d like better vaccine and in fact there's lots of research going on towards improving influenza vaccines by novel approaches like looking at different proteins on the surface of the vaccine or different areas of the protein on the surface of the vaccine. The goal clearly is to find a vaccine against influenza that you don't have to give every year that works better and can work for more people. I think there's hundreds of labs around the world and hundreds of field sites around the world that are actively studying this area. So hopefully in the next several years we'll get those greater vaccines. In the meantime, we have better and better vaccines every year. Dr. Frieden mentioned the fact that we have four-valent, or quadrivalent vaccines that will be here next year. We have vaccines that are injectable and some are sprays through the nose. And so we're making it easier and easier I hope to get the vaccine because there are more choices to get the vaccine. And now as you say the challenge is to make the vaccine better.
TOM SKINNER: Next question, please.
OPERATOR: Thank you. Next question comes from Lena Sun with Washington Post. You may ask your question.
LENA SUN: Hi. Thank you very much. I had a couple of questions. One, do you have updated numbers on how many people have actually been vaccinated? I know that the most recent number I have seen was from back in November, 112 million. That's one. The second question is -- this is going back to the vaccine effectiveness, to put it in context. How does the 62 percent this year compare to the last couple of years? And three, I know it's very complicated as to why, but I was wondering if you could take a brief stab at explaining for the lay reader why it's so hard to get an effective flu vaccine when, you know, childhood vaccines are like at 90 percent and higher?
JOE BRESEE: Yeah, thanks very much, Lena. If I tracked your questions correctly, let me answer the first one which is coverage. The latest coverage -- the true coverage survey numbers we have are the ones I mentioned from mid-November. We do track the doses distributed in the United States, which as of January 4th was 128 million. And we'll track that in an ongoing way. The next coverage numbers will be available in March of the year. That will really be -- get us to where -- towards the final numbers for the year. The second question is how does the VE compare with previous years? It compares about the same. I think if we have looked at the last several years our VE numbers are variable, like everything with flu. Last year was in the mid-50s. Some years are lower, some are higher.
If you look back and try to look at the vaccine effectiveness studies that have been done over the last 20 years, the 50 to 70 percent range is a reasonable range. Flu vaccines are tough as you say. If I had the perfect answer of how to make a better flu vaccine, I’d probably get a Nobel Prize. But flu vaccines are tough and one of the problems are that the flu virus changes all the time, number one. Because it mutates so often, we have to keep up with the vaccine really often. The second -- the second thing is that the antibodies that we get when we get the flu vaccine go away. And so we get a nice rise of antibodies that will take us through the flu season but tend to decline towards the end of the flu season. Another reason you have to be revaccinated every year. But I think the nature of the flu viruses -- the fact they're all changing and the complexity of our immune response -- makes the vaccines difficult to develop the 100 percent vaccine we are looking for.
TOM SKINNER: Next question, please. We have time for maybe two or three more questions.
OPERATOR: Thank you. Next question comes from Timothy Martin with Wall Street Journal. You may ask your question.
TIMOTHY MARTIN: Hi. In the MMWR, there was a mention that approximately 60 percent has been the number of the estimated effectiveness of these vaccinations from randomized clinical trials. Is that for this year's flu shot and if not, if it's looking at previous flu shots, can you tell me what's the rough time frame with which those trials were conducted? And the second question I have is: have you guys compared the flu season this year which arrived earlier than in recent memory versus say the last time the flu came this early and if there's anything different, you know, as we head into January and February? Thank you.
JOE BRESEE: I think the number you're referring to of the randomized control trials was the number that we referenced from a recent review or meta-analysis of randomized controlled trials done recently and published I think last year. Those studies were done over probably a couple of decades. I'll have to look it up. But substantially the randomized controlled trials aren’t done this year. What we reported this year is what we call observational trials and those are studies that we do that are not randomized. So what we do is we go to the hospital or a clinic and we look for disease and then we measure how many people have been vaccinated, compare them to people who don't have the disease, and look for vaccination rates, and then compare those two. Sort of a ratio.
Randomized control trials are done and they're excellent -- they're excellent ways to measure the best effect of the vaccine. The observational trials you think about as a way to measure the true effect of the vaccine when given in a vaccination program to a program. Your second question was how does this season compare to previous early years? The best comparator year was the 2003-2004 year which was also an early year. In fact that year was much earlier than this year and we had peak disease in November and December of that year. It was also an H3N2 predominant year and that was also in the end associated with a lot of mortality and a lot of pediatric mortality as well. I don't know how this year will compare in terms of severity or in terms of length or in terms of when the peak is to that year yet. But we'll know in a few months.
TOM SKINNER: Next question, please.
OPERATOR: Thank you. Next question comes from Rachel Rettner with myhealthnewsdaily.com.
RACHEL RETTNER: Thank you for taking my question. You mentioned that the percentage of deaths attributed to pneumonia and influenza is above epidemic thresholds. I was wondering if you could explain what you mean by above epidemic thresholds. Does that mean we are seeing more deaths than usual?
JOE BRESEE: That’s a good question. We measure those deaths according to what we call a regression model. And what we do is we map over many years the rise and fall of influenza by season. And the rise and fall of all deaths by season. What we then construct is a model, a statistical model, to allow us to know when we think flu is circulating, or when we think the flu is resulting in the deaths that we're looking at. One way to do that is to create these models that have a baseline and if you look at that graph, you see a lower solid line that goes up and down over the years. Then you create a threshold and the threshold in this case is about 1.8 standard deviations above the baseline. So the baseline is if you had to draw sort of an average of all the deaths that occur over the year that's the baseline. The threshold is above that. What we've found out is that when the P&I, the pneumonia and influenza deaths, exceed the epidemic threshold, that's when flu tends to circulate and we can think that flu is associated with the deaths that exceed that threshold. And so basically, think about it as a way to know when the timing of severe disease is in the United States.
TOM SKINNER: Shirley, we'll make this our last question, please.
OPERATOR: And our last question then comes from Bob Roos with CIDRAP News. You may ask your question.
BOB ROOS: Thank you. I've often heard it said if you get vaccinated but you still get the flu, you may get a less severe case. That vaccination may provide some protection from the severe virus. Do you have a sense if that's happening this year?
JOE BRESEE: I think that's a good question and there are some data to indicate that getting the vaccine gives you a -- could give you a milder disease if you do get infected. The data is very sparse though. It makes sense to me that it's true and it might explain why there's lots of disease so far at least, and less disease. But the proof is towards the end of the season, about how much disease we see.
TOM SKINNER: Okay. Thank you all for joining us. This concludes our call. Should you have follow-up questions or want an interview with Dr. Bresee or another subject matter expert, please call the CDC Press Office at 404-639-3286. There will be a transcript available of this telebriefing by later on this afternoon. So thank you for joining us and we will keep you updated as the flu season unfolds. Thank you.OPERATOR: Thank you. Thank you for participating in today's conference. We thank you for your participation. You may disconnect your lines at this time.
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