CDC Telebriefing: Update on Flu Activity and Vaccine Effectiveness Estimates
Press Briefing Transcript
Wednesday, February 20, 2014 12:00 PM E.T.
OPERATOR: Welcome and thank you for standing by. At this time, all participants are in a listen-only mode until the question and answer session of today's call. At that time, if you would like to ask a question, please press star 1. Today's conference is being recorded. If you have any objections, please disconnect at this time. I would like to turn the meeting over to tom skinner. You may begin, sir.
TOM SKINNER: Thank you Simone. Thank you all for joining us today for this telebriefing, an update on influenza. Where we'll be discussing several articles that appear in today's Morbidity and Mortality Weekly Report. With us today is the director of the CDC, Dr. Tom Frieden, as well as the director of the National Center for Immunization and Respiratory Diseases, Dr. Anne Schuchat. Both will provide some opening remarks, then we'll get to your questions. Dr. Frieden?
TOM FRIEDEN: Thank you. Thank you all for joining us this afternoon. I'd like to start by giving the basic bottom line here. And it's this -- influenza can make anyone very sick very fast, and it can kill. Vaccination every season is the single-most important thing you can do to protect yourself. Now, so far this season, we have seen flu hitting middle-age and younger adults hard. The season is likely to continue for several more weeks, especially in parts of the country where flu activity started later in the season. Some states saw earlier increases in flu activity than others, and those places are beginning to see decreases. But other states are continuing to see high levels or are seeing continued increases in flu activity.
Each year we look at what the predominant strain of flu is. In this week's MMWR, we have three separate reports on influenza. One on vaccine effectiveness that Dr. Anne Schuchat will speak about in a moment. A second on the overall pattern of flu in the U.S. and a third, an in-depth look at some of the most severe and fatal cases of flu in California. This year, flu activity has predominantly been H1N1. That's the same strand of influenza that caused the pandemic in 2009, and it has not mutated substantially. It's back this year, and it's hitting younger people hard. One of the reasons it's hitting younger people hard is that the vaccination rate for young adults 18 to 64 is too low. Even by November, the vaccination rate for seniors was more than 60 percent. The vaccination rate for young children was more than 50 percent. And last year that vaccination rate for young children got to nearly 80 percent by the end of the season. But by November, only a third of 18 to 64 year olds had been vaccinated. That's one of the reasons we're seeing a much higher proportion of hospitalizations and deaths among 18 to 64 year olds than we generally see. And we see this particularly in people who are 18 to 64 who have underlying medical conditions, such as lung disease, asthma, diabetes, and obesity. And I’ll point out in passing here that another article in this week's MMWR gives a very encouraging result of reducing childhood obesity in King County, Seattle, through an obesity prevention project. But for people who are of any age, vaccination is the single-most important thing you can do to protect yourself against the flu. And for people who are sick with the flu, the California analysis has a very important message for doctors taking care of someone who's sick with symptoms that might be the flu. If they're very sick, don't wait for a test. Don't not treat if the test is negative. If you think clinically it might be flu, treat for flu promptly. Unfortunately, we're seeing that only a small proportion of people who are severely ill and have flu are treated for flu promptly. And that can make a difference.
First line of defense, vaccination. Next line of defense, prompt treatment for people who are severely ill, especially if they have underlying conditions. Because influenza can make people very sick, very fast, especially people who have health problems. This season's pattern of more hospitalizations and more deaths in younger age groups is likely due to existing levels of immunity in different age groups. So another way to put that is, for the younger people, we have higher vaccination rates. For the older people, we have immunity that was probably obtained from infections with flu strains similar to H1N1 that were circulating decades ago. The 2009 H1N1 virus is estimated to have caused more than 60 million illnesses among people in the U.S. in that first year. But that still left the vast majority of Americans vulnerable. Only about 40 to 45 percent of people in the U.S. get vaccinated each year, and how well the vaccine works varies. You'll hear from Dr. Schuchat that for H1N1, the strain that's out there this year, the vaccine works pretty well. I'll close by saying that flu hospitalizations and deaths from influenza in young and middle-aged adults are painful reminders that flu can be serious for anyone, not just for infants and the very old. And everyone should be vaccinated. The good news is that this year's flu vaccine did its job. It protected people across all age groups. I'll now turn the call over to Dr. Anne Schuchat to give more information about how well this year's vaccine protected people, about which groups are at particularly high risk from flu and the importance of prompt treatment with anti-viral drugs in people likely to have flu. Dr. Schuchat?
ANNE SCHUCHAT: Thank you, Dr. Frieden. I'm glad to be following this sobering update on the flu activity we've been having this year with what I say is reassuring news about this season's vaccines. This season's vaccines did their job, providing solid protection to people across all age groups. We know that how well the flu vaccine works can vary by season, by the virus type, by the vaccines that we're using as well as by age and other characteristics of the people being vaccinated. So each season, each flu season, CDC is conducting studies to measure the performance of seasonal flu vaccination that helps us determine how well flu vaccines are working in actual use in the United States. These studies measure vaccine effectiveness. And today's MMWR reports our interim vaccination effectiveness for the current flu season.
The team looked at data from 2,319 people, including both children and adults who were identified through the U.S. Influenza Vaccine Effectiveness Network from December 2nd, 2013, to January 23rd, 2014. So these are our interim results, and we'll be reporting the final results later this year. We found that flu vaccine reduced the risk of having to go to the doctor for lab-confirmed influenza illness by an estimated 61 percent across all ages. That means if you were vaccinated, you are quite likely to be protected from the flu viruses that have been circulating this season. This year's vaccine gave significant protection to all age groups. Vaccine effectiveness point estimates range from 52 percent for people 65 and older to 67 percent for children 6 months to 17 years of age. This year's estimates for the interim adjusted vaccine effectiveness against just the H1N1 illness are comparable to the estimates we got for effectiveness of the monovalent H1N1 vaccine we used back in 2009 during the pandemic, and they're also comparable for seasonal vaccines in years when the vaccine is well matched to the circulating strains. They're also similar to estimates that Canada just reported for this season. CDC will continue to monitor the vaccine effectiveness throughout the season. And I want to remind you that the season is not over and things could change.
As you know, CDC and the Department of Health and Human Services are committed to the development of better flu vaccines, but existing flu vaccines are the best preventive tool available now. Today's report shows that this season vaccinated people were substantially better off than people who did not get vaccinated. And I want to remind you all that there's still a lot of influenza circulating. So if you haven't been vaccinated yet, it's not too late for you to benefit from getting vaccinated. CDC recommends everyone 6 months and older get an annual flu vaccine, and that includes pregnant women and others who are at higher risk of serious complications from flu. I know some of you have been reading those reports about terrible outcomes in otherwise healthy young people. Today's estimates remind us that some vaccinated people will become infected with influenza despite vaccine been vaccinated. I want to remind you that anti-viral medicines should be used as recommended for treatment in patients regardless of vaccination status. So today we've heard that influenza can be serious, even for nonelderly adults, and that this season's vaccines are providing solid protection for people of all ages. So I’d like to turn things back over to our moderator, and we can take questions.
TOM SKINNER: I believe we're ready for questions, please.
OPERATOR: Thank you. We will now begin the question and answer session. If you would like to ask a question, please press star 1. Record your first and last name clearly when prompted. Your name is required to introduce your question. To withdraw your question, you may press star 2. Once again, if you would like to ask a question, please press star 1. One moment while we wait for our first question. Our first question comes from Mike Stobbe, The Associated Press.
MIKE STOBBE: Hi. Thank you for taking the question. Could you all speak a little more to why did H1N1 swine flu kind of move backstage after 2009-2010, and why did it come forward now? Do we know why?
TOM FRIEDEN: I’ll start and then ask Dr. Schuchat to add to it. What we see with many infectious diseases is what we sometimes call an accumulation of the susceptible population. Young children, infants born after the H1N1 pandemic in 2009, have not been exposed to it. So we have a cohort of young children, albeit many of them now vaccinated, but many of them not, who are susceptible to H1N1. Also, there may be some pooling or declining susceptibility or declining immunity, rather, in society as a whole. So basically, our societal resistance to this particular strain may be lower than it was before. Dr. Schuchat?
ANNE SCHUCHAT: Yeah, thanks for that question. It's one of the many mysteries of influenza that it's of course always hard to predict what's going to happen in a given season. This is the first season that the H1N1 strain has dominated since 2009 here in the United States. But we've actually seen different patterns in different countries. There are some countries that had quite a bit of H1N1 after the pandemic, and the U.S. didn't. We think that what happens is a mixture of population immunity, vaccine coverage, and probably mystery factors that we just don't understand. So I think that it is important to know that this year we had vaccines before high rates of disease were circulating and we think that's a principle difference in how the season is evolving here compared to 2009. That this year we are able to take advantage of the many people who get vaccinated. We just wish more people would get vaccinated.
TOM SKINNER: Okay. Mike. Do you have a follow-up?
MIKE STOBBE: No, that's it. Thank you.
TOM SKINNER: Next question, please.
OPERATOR: Certainly. Our next question comes from Dan Childs, ABC news. Dan, your line is open, sir.
DAN CHILDS: Hi, thank you so much for taking my question today. Sort of a two-part question to start with. You know, you were talking about how effective the vaccine has been this year. How does that stack up with regard to the vaccination effectiveness of years past? Kind of related to that, how many doses of this vaccine are actually left for those who have not gotten their shots yet?
ANNE SCHUCHAT: So the vaccine effectiveness varies year to year, and that's a mixture of the strains that are circulating and the particular vaccine that's made up. As you know, there's new vaccine made every year. And people do need to get a flu vaccine every single year. In the past several years we've seen a range of about 35 percent to over 60 percent effectiveness. I can tell you the Canadians estimated about 70 percent effectiveness for this year. Quite a bit of that difference depends on which strains are dominating and how well the vaccine is matched to the circulating strains and also who's being vaccinated. In places where it's mainly healthy young people being vaccinated, effectiveness tends to be a bit higher. The second question was about, I believe it was about the doses that have been distributed. So far this year, we think about 134 million doses of influenza vaccine have been distributed. The companies were expecting to make a few more million doses, about 138 million or more. So they are continuing to produce and distribute. It may be difficult to find flu vaccine near where you are. There are some tools available that you can find on the web to look at where flu vaccine is. But you may have to call a couple places. What I would say is that it isn't too late. And in particular for parents whose children are under 9, your child might need a second dose of vaccine, so you may want to ask their doctor about that.
TOM SKINNER: Next question, please.
OPERATOR: Certainly. Our next question comes from David Beasley with Reuters news service. Your line is now open, David.
DAVID BEASLEY: Yes. Could you tell us how many people have died in the U.S. from the flu this season so far?
ANNE SCHUCHAT: Thanks for that question. That's a really important question. Unfortunately, we can't answer that yet. Our team has been doing estimates of the deaths from influenza, but they're not available yet for this season. Of course, we're still in the middle of it, and it's really too soon for us to know how things will shape up. Last year was a tough year. There was a high impact of influenza last year. And we know that about hundreds of thousands of people, we believe, were hospitalized from flu last year. And quite a few people died. But what I would say is that later this year, later this calendar year, we hope to be providing more up-to-date estimates of influenza deaths this season. In the past we've said it can range from about 4,000 to about 50,000 annual deaths from flu. Very variable. And of course, the more people we vaccinate, the fewer deaths we think we'll have.
DAVID BEASLEY: If you estimate 60 percent of the flu deaths were of patients between the ages of 24 and 64 -- I believe that's what the MMWR said.
ANNE SCHUCHAT: There’s a report in the MMWR from the California health department looking intensively at their severe disease and death surveillance. Their severe disease and hospitalization surveillance focuses on people under 65, so it's difficult for us to project from that to the national proportion of deaths that will occur in the elderly. We are seeing excess deaths this season. You know, for five weeks in a row we've had the pneumonia and influenza mortality statistic had been above the epidemic threshold. That's a sign to us it's more than a typical season. But we do have excess deaths going on, but we don't have a tally yet this year.
DAVID BEASLEY: One quick other question. If we don't know exactly how many other people have died, how can we estimate that the younger adults and middle-aged folks have been hit harder?
ANNE SCHUCHAT: We have a number of things that are comparable. We are looking at our hospitalization data annually and seeing that rates of hospitalizations in people under 65 through this point in the year are high. We're also seeing that higher proportion of hospitalizations in the nonelderly. That, of course, is a mix of things. It's a mix of less hospitalizations potentially in young children because they're heavily vaccinated and perhaps less hospitalizations in the seniors who are both usually vaccinated and then also may have that long-standing immunity. So it'll take some time for us to really stack things up. I think anecdotally, many people are aware of very high-profile tragic deaths that we're seeing in completely healthy people. A reminder that flu can be very serious, even in healthy adults.
TOM SKINNER: Next question, please.
OPERATOR: Our next question comes from Miriam Falco, CNN, Atlanta. Your line is now open.
MIRIAM FALCO: Thank you. Hi, Dr. Frieden. Hi, Dr. Schuchat. This is following up on what you were just saying which is, this has got to be extremely frustrating for CDC public health officials and elsewhere when you know you have a vaccine that has a good match to what's the main circulating strain of flu. Yet, people aren't getting the message. It's probably too early for you to figure out how to do this differently next year, but it seems -- where's the disconnect? We have a vaccine. It's something that can really protect you, really being 60 percent, but that's good for flu vaccine. And yet, people aren't doing it. Are doctors not talking to patients -- to their patients? Are people not hearing the message when you guys are talking about it? There are plenty of apps out there, all kinds of flu apps that are supposed to track things for you. What do you think needs to be done to prevent this type of unfortunate situation?
ANNE SCHUCHAT: You know, thank you for that question. We think parents got a wake-up call in 2009, and we've seen tremendous progress in pediatric influenza vaccination coverage since the severe disease that was prevalent in 2009 during the pandemic. And with adults, it's a newer recommendation. We actually recommend every adult gets vaccinated every year. That hasn't been going on for 20 years. That's a relatively new recommendation. But we do think that the media, the public attention, friends and family can help. We think the most motivating factor is knowing that you can protect your loved ones by being vaccinated. That is helping get the word out. But vaccination isn't just a doctor thing. Vaccination is now available at workplaces, at pharmacies, shopping centers, as well as of course in the doctor's office and clinics. And we really are keen to get -- to make it very easy for people to be vaccinated and for them to know how much they can benefit and how it can help them get the things they want to get done every year as well as protect their family.
TOM FRIEDEN: And I think as you say, it is frustrating that we have something that would be preventing many more illnesses, hospitalizations and deaths, but isn't as widely used as we wish. Any preventable death is a tragedy. We all need to do everything we can to prevent as many illnesses and deaths as we can.
ANNE SCHUCHAT: I mean, we'd like to avoid you having to know somebody who's tragically died from flu who wasn't vaccinated in order to realize it's a good idea to be vaccinated. I mean, our goal is to not have a scare story make you do the right thing.
TOM SKINNER: Next question, please.
OPERATOR: Certainly. Our next question comes from Elizabeth Weise with USA Today. Ms. Weise your line is open.
ELIZABETH WEISE: Hey, thanks for taking my call. Hey, guys. So, looking at these numbers, for the higher hospitalization rates and presumable death rates among working-age adults, what's the percentage of those with underlying illness? I know early in the season it looked like obesity was the single largest factor for severe illness. What was the final breakdown?
ANNE SCHUCHAT: Yeah, for our hospitalizations in our national data, the vast majority of hospitalizations in adults are in people with underlying conditions. About -- only about 15 percent of adults who are hospitalized didn't have a medical complication or illness. Whereas children, you know, 43 percent of children who are hospitalized had no complicating -- had no other medical factor. The California data are smaller numbers, but more than 90 percent of the severe hospitalizations, the ICU hospitalizations and deaths in California, in the nonelderly, were in people with medical conditions. So I think there is a reminder that even healthy people can die from the flu or be hospitalized, particularly children. But it's very important to say we can't predict who's going to get a severe outcome. Unfortunately today, a lot of Americans have other medical conditions, and we want them to be protected.
ELIZABETH WEISE: And actually, a follow-up on that. So, in the universe of people who had underlying conditions, what percentage of those were folks who were obese? Because that was very high early in the season.
ANNE SCHUCHAT: Right. So for the national study, it's 43 percent of the adults were reported to have obesity. Morbid obesity. With a body mass index over 30. I don't actually -- okay. So this is not actually -- we'll double check whether it's morbid obesity or not. It's in this week's FluView, which is on our website. But I don't actually know what the national estimate for obesity is. So that's a little bit higher, but we know that there are way too many. Obesity is a big problem. It's not like there's zero obesity out there and it's just in the flu cases. It's a national problem.
TOM SKINNER: Next question, please.
OPERATOR: Our next question comes from Eben Brown, Fox News Radio. Eben, your line is open, sir.
EBEN BROWN: Thank you very much, and thanks for the call today. I got a flu shot back in November. Is that one valid still for H1N1, or is that outmoded and should I get another one at this point?
ANNE SCHUCHAT: We don't recommend that you get another one. We think that the flu vaccine you got in November should still be protecting you today. We do think that children under nine who have never gotten a flu vaccine before generally need to get two doses the first year they're getting flu vaccine. But for everybody else, it's just one vaccine a year. But one vaccine every year.
EBEN BROWN: Well, okay. So when we're talking about years, we're talking about seasons. Like I said, November. That was last year at this point. So when is a good interval, is probably the best question to ask.
ANNE SCHUCHAT: Right. We in the influenza world talk about years differently. I'm sorry for that. Once the vaccine begins to be offered in August or later, that vaccine is good through the whole season, which can go as long as May. There's new vaccines that come out every summer, and that's when we switch over. So your November dose is just fine through this influenza season, which some years last from, you know, October all the way to May.
EBEN BROWN: Great. Thank you.
OPERATOR: Our next question comes from Ryan Jaslow, CBS News. Ryan, your line is now open, sir.
RYAN JASLOW: Thank you so much for taking my question. I know you mentioned the November estimates for vaccination rates, but I was curious if you guys had any numbers or any preliminary sense of how many people among the 18 to 64 hospitalization group were vaccinated versus unvaccinated.
ANNE SCHUCHAT: We don't have more recent data on that since the November estimate, but we know year in and year out that age group is the least likely to be vaccinated compared to children and seniors. We do usually see an increase from the November midseason estimate of coverage to the end of season estimates. So we'll be looking for them through the rest of the spring. But we don't have updated data on that yet.
RYAN JASLOW: Thank you.
TOM SKINNER: Next question, please.
OPERATOR: Our next question comes from Rob Stein, National Public Radio. Your line is open, Rob.
ROB STEIN: Yeah, hi. Thanks for taking my questions. Two questions: One was a follow-up to an earlier question about the deaths. I'm just trying to understand. If you're saying that 60 percent of the deaths are among this age group of 25 to 64, how do you know that if you don't know how many deaths there have been? Where do you come up with that 60 percent figure? And then the second question is another number question, which is the relatively low rate of vaccination in that age group, how does that this year how does that compare to previous years?
ANNE SCHUCHAT: Right. Let me do the questions in reverse. The low rate of vaccination in the 18 to 64 is consistent with previous years. We are -- the elderly are very good at getting vaccinated. We've been at the 60 percent to 70 percent coverage for the elderly for some time now. And children are really moving up with more than 50 percent of children getting vaccinated each year. As Dr. Frieden said, under two, it's more than -- nearly 80 percent that get vaccinated. The question of how do we know the percent of deaths that are in a different age group without knowing the total number of deaths, our information on deaths comes from 122 cities that promptly report to us death certificate data where pneumonia or influenza is a cause of death. We look at pneumonia and influenza as a cause of death among all the deaths that are reported that week in the 122 cities. We look at the percent of deaths that are over the seasonal expected, and that's how we come up with an epidemic threshold. We do have data for that sample of 122 cities in how many people have died with a pneumonia and influenza death attributed to it and what their ages are, but that's just a sample. When we want to come up with what the full season, national picture of influenza deaths is, we need the end-of-season data for that.
TOM FRIEDEN: I think it also is important to clarify that we have several different ways of looking at deaths. One is to see how many deaths actually have flu written on the death certificate. That is a very substantial underestimate of flu deaths, because particularly in the elderly, flu can trigger heart problems, lung problems, pneumonia, and so the issue of total flu deaths is something that needs to be not just counted but also modeled to be accurate.
ROB STEIN: If I could follow up with a quick question on the first question, immunization rates. So, you're saying that the rate in this age group is about the same as it's been, it's not lower than usual, so it sounds like it's the lack of natural immunity to the H1N1virus that is playing a role in that age group getting hit harder. Is that right?
ANNE SCHUCHAT: Yeah, we think that children probably were more likely to have both natural immunity and vaccine-induced immunity than the middle-aged adults. And that the seniors both have a high likelihood of being vaccinated but also probably have that long-standing immunity that we talked about. So the middle-aged adults probably neither -- you know, they're less likely to have natural immunity and less likely to be vaccinated. We believe that's what is likely going on right now. But of course, you know, the season's not over and there may be other strains that become important as the weeks go on.
ROB STEIN: Great. Thanks much.
TOM SKINNER: Next question, please.
OPERATOR: The next question comes from Robert Lowes. Robert, your line is now open, sir.
ROBERT LOWES: -- come into play when the CDC makes a good match between the vaccine and the strains that it expects to be circulating. If you can take that first, then I’ll ask my other question.
ANNE SCHUCHAT: You cut off. Could you repeat the question, please?
ROBERT LOWES: Oh, yes. What are the factors that come into play when the CDC does well or succeeds in making a better match between, you know, the circulating strain or what you expect to be circulating and the vaccine?
ANNE SCHUCHAT: Okay. Thank you. You know, the influenza vaccines are made up every year based on a prediction of what strains are likely to circulate. CDC participates in that strain selection. And the strain selection is based on a huge amount of laboratory work and data analysis of strains that are circulating late in the season before around the world. So that's looked at for the northern hemisphere all at one time, in fact this week, and it's looked at for the southern hemisphere all at one time, you know, about six months from now. And the more strains that are part of that review and the more sophisticated tools we have now to do that review, the more accurate our prediction is. But it's not perfect. It's very difficult to predict the B-strains, and for that reason in recent years, there's been an opportunity to put two different vaccine B-strains in some vaccines. You may have heard of the quadrivalent vaccine. But this year the incorporation of the H1N1 strain looks like it's a very good match to the circulating H1N1 strains. So probably this is art and science that's involved with predicting the strain, but I do know that the huge investments in better surveillance for influenza around the world, and participation of more and more countries in influenza surveillance and strain sharing is letting us do much better prediction the past few years.
ROBERT LOWES: And my other question has to do with, I guess, perhaps myths that exist in the medical community regarding safety of vaccination for pregnant women. I know that the evidence shows that women are safe -- pregnant women are better off being vaccinated than unvaccinated. But is there a myth in the medical community that women early in the pregnancy should not be vaccinated for influenza? Is that some kind of leftover belief from years ago? Because it apparently popped up in the case in Arkansas where a woman died after she got the flu. She was pregnant. She was told by her doctor not to be vaccinated early in the pregnancy. And I wondered if this is you've heard of this kind of advice before from physicians.
ANNE SCHUCHAT: We recommend influenza vaccine for every pregnant woman regardless of the trimester. Certainly physicians and pregnant women have anxiety about what they do during pregnancy. We think that anxiety is generally good. You know, they should stop smoking. They should not drink alcohol. And it is important to keep track of what you're eating and what medicines you're taking. But CDC strongly recommends, and the American College of Obstetricians and Gynecologists strongly recommends influenza vaccine every year for pregnant women, regardless of trimester. So as soon as the vaccine is available, we recommend pregnant women get it. We know it won't prevent every single problem, but women should know that it's safer for them and the baby to be immunized against influenza.
ROBERT LOWES: But doctor --
TOM FRIEDEN: The other point -- two points to make is, we have encouragingly seen a steady increase in the proportion of pregnant women vaccinated. There was a bump during the 2009 pandemic when there were tragically and highly publicized cases of pregnant women who died from flu. And that gain has been sustained and increased. Second point to make is that we've worked with the American College of Obstetricians and Gynecologists and with practices, and it's very clear that if the obstetrician carries the flu vaccine in her or his office and provides it on the spot to patients, you get a much higher rate. So, in fact, the biggest barriers we see to further increases are in the health care system that supports patients. It's not so much in patient reluctance.
ROBERT LOWES: So you're not encountering a myth among doctors that early vaccination in early pregnancy is problematic?
ANNE SCHUCHAT: There’s a lot of myths and misinformation, and I think it's our goal to get the best information out there. You know, we know that the flu vaccine doesn't cause flu, but some people worry that it might. We think that obstetricians have been getting better and better, but there's still room for improvement. And I know that any time you've seen a tragedy like the one you described, it sticks with you. We really hope that everyone can learn from that and can try to make sure that the pregnant women they know and love get their flu vaccines.
ROBERT LOWES: Thank you.
TOM SKINNER: Next question, please.
OPERATOR: The next question comes from Bob Roos, CIDRAP News. Your line is open, bob.
BOB ROOS: For comparison purposes, I was just wondering what the final vaccine effectiveness estimates were for last season. Also, just wondering if you in this year's estimates, if you tried to assess whether protection waned at all with the -- after a longer time from vaccination that is any sign of protection that wanes after three months or so.
ANNE SCHUCHAT: Thanks. The final end of season for 2012-'13 from the CDC network was 52 percent with confidence intervals from 46 to 58. We don't at this season yet have information about any kind of waning over the current season. As I mentioned, these are our interim estimates just through the January time point. So there's a lot more analysis. I don't believe I remembered to say this, but practically all of the strains that were causing illness in the people in our study were H1N1. So we're really not going to be able to get you, you know -- so far anyway, we're not going to get an estimate for effectiveness against the H3N2 unless the season changes a lot in the next month or so. But the end of season last year ended up at significant protection at 52 percent. You know, this year so far it's 61 percent.
BOB ROOS: Thank you.
TOM FRIEDEN: And we do generally see the vaccine being a bit more effective against some strains than others, particularly in the elderly, H3 perhaps a little less effective than H1, this year we have H1 as the predominant strain, and H1 well matched in the vaccine.
TOM SKINNER: Simone, we’ll take a few more questions.
OPERATOR: The next question comes from Donna Young, Scripps News.
DONNA YOUNG: Thank you for taking my question. I had first a clarification on the one sentence in the MMWR that's talking about the 2009 pandemic. It talks about that it counted for 98 percent of the flu viruses detected. Then it talks about the effectiveness with 62 percent. So is that sentence there, is the 62 percent talking about this season or the 2009 season? Then I had a question on the quadrivalent vaccine.
ANNE SCHUCHAT: Yeah, let me take your first question first.
DONNA YOUNG: Thank you.
ANNE SCHUCHAT: The 62 percent is for the H1N1 strains this season. So the overall was 61 percent, and then when you focus in on only the study participants that had H1N1, it was 62 percent. You know, if you look at the table, it's just -- the sample size is just a little smaller for H1N1 only, but it's talking about this 2013-'14 season.
DONNA YOUNG: Thank you for clarifying that. And then the other question I had was when you were doing these estimates, did you break out the differences between the effectiveness of the quadrivalent vaccine versus the trivalent? So, like, is there a separate estimate? Is the 61 percent, is that total for the trivalent and quadrivalent together?
ANNE SCHUCHAT: It’s total for any influenza vaccine that people got. Often by the end of the season we'll try to see whether we have enough of different formulations to matter, but I can tell you that the H1N1 strain -- vaccine strain in the trivalent and quadrivalent are the same. And so we would expect similar effectiveness. Sometimes by the end of the season we're able to look at the live attenuated vaccine versus the inactivated vaccine. We rarely -- we so far haven't had big enough numbers to be able to look at the high dose versus the regular dose. But the MMWR is reporting any influenza vaccine for the 2013-'14 season.
TOM SKINNER: Simone, we’ll take one more question, please.
OPERATOR: Okay. Our final question comes from Helen Branswell, the Canadian Press.
HELEN BRANSWELL: Hi. Thanks very much for taking my question. I actually have two, if I could, please. The first relates to the vaccine effectiveness data. The U.S. is reporting 61 percent for total vaccine and 62 percent for the H1N1 component. You said that's similar to the Canadian numbers, but the Canadian numbers were actually higher, 71 percent for all vaccine and 74 percent for the H1N1 component. How do we make sense of the difference there, and I have a follow-up if I could, please.
ANNE SCHUCHAT: Yeah, you know, the way that I -- my speculation for the difference is that the population in the Canadian sentinel surveillance was a bit younger than our population. So that the age-specific effectiveness isn't as different as the overall. You know if you look at the effectiveness that's measured in each age group. Maybe there are other reasons, but I think that's one possibility. We know that in our study, although the vaccine was effective in every age group, it was more effective in the youngest and then next most effective in the middle and then least effective, although still effective, in the seniors. So that's my interpretation. You had another question.
HELEN BRANSWELL: Yeah, it relates to durability of protection from a flu shot. What's really known about that? Because as I’m sure you know, the W.H.O., the strain selection for next winter's flu shot was going on this week at W.H.O. and today they announced the composition of the flu shot. And it's going to be exactly the same as the composition of this year's shot. So, you know, do we actually know that people who got a flu shot this year will need a flu shot next year?
ANNE SCHUCHAT: Thank you. The durability of influenza vaccine is a hot topic, and there continues to be emerging data on that. We strongly recommend people get influenza vaccine every single year whether the flu vaccine changes or not. We know that duration of protection for any vaccine can vary by individual. I would hate to assume that my vaccine from last year was going to protect me next year, and I personally am going to get a vaccine every year and recommend it to others.
TOM FRIEDEN: Thank you all very much -- Tom Frieden -- I'll just close by thanking you for joining us and reiterating some of the key messages from this week's MMWR on flu. First, that this season is hitting middle-aged and younger adults hard and the season is likely to continue for some time. It's not too late to get a flu shot. One of the reasons it's hitting younger adults so hard is that such a low proportion of younger adults get the flu shot, even those who have elevated risks from underlying health conditions such as diabetes, obesity, COPD, and asthma. Second, that this year's flu vaccine is working. It's not working as well as we wish it would, but a 60, 62 percent vaccine effectiveness in all age groups is encouraging. Third, and particularly for the health care providers, that people who come to the health care system with severe illness, especially if they have underlying conditions, that may be flu, treat early. Because that may make a big difference in how likely that person is to go on to develop even more severe illness. So influenza can make anyone very sick very fast, and it can kill. Vaccine is the single-most important thing you can do to protect yourself. Thank you all for joining us today.
TOM SKINNER: Simone, this concludes our call. Thank you all for joining us. For reporters needing additional information or questions answered, they can call the CDC press office at 404-639-3286. Thank you all for joining us.
OPERATOR: This now concludes today's conference. All lines may disconnect at this time.
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- Page last updated: February 20, 2014
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