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Vietnam: H5N1 variation (clade 2.3.4) vaccines powerless
Friday, 02/17/2012 22:32
The avian influenza virus was genetically engineered into the new virus is highly virulent, contagious and resistant to vaccines. While Vietnam does not have A/H5N1 flu vaccine on humans
While bird flu continues to spread to many provinces, the deadly virus have been many changes detrimental to the prevention and treatment measures in poultry. More worrying when the death rate from influenza A/H5N1 in humans is 100% of cases are detected.
Resistant virus vaccine
On 17-2, Hoang Van Nam, Director of Animal Health authority (Ministry of Agriculture - Rural Development), said from the beginning of this year has 11 local detection of avian influenza including Thanh Hoa, Quang Tri, Soc Trang, Ha Nam, Hai Duong, Thai Nguyen, Kien Giang, Bac Giang, Ha Tinh and Hai Phong and Quang Nam.
Not yet quarantined poultry still be comfortable buying and selling, slaughtering in Hanoi
There were nearly 20,000 birds, mostly ducks to be destroyed. The bird flu is complicated, spread in all 3 regions. If loose slaughtering operations management, transportation and trade of poultry, the risk of widespread outbreaks is huge.
Risk of spreading bird flu, today (18-2) National Steering Committee for prevention of avian influenza will have an emergency meeting to discuss measures to cope. Meanwhile, Mr. Diep Kinh Tan on 17-2, Deputy Minister of Agriculture - Rural Development, said it had written to the Prime Minister requests the State budget of 13 billion contract to buy 50 million doses of H5N1 vaccine Re-vaccination strains fifth round of 1-2012 for timely enclosure, stamping out.
According to Tan, 2012 is expected to need 327 million doses of vaccine given to poultry, but due to bird flu virus in the northern provinces with the change, the vaccine strain H5N1 Re-5 protection levels households is not high. Meanwhile, in the southern provinces, not bird flu virus is modified to use H5N1 vaccines imported from China, so immediate permission to import 50 million doses.
The risk to humans is very large
According to experts, the bird flu virus may be genetically caused the surveillance becomes more difficult. Department of Animal Health representative said before, there are 3 branches Vietnam H5N1 virus has been detected. A branch in the south, north branch and the branch 2.3.4 7 capable of highly infectious.
However, recently in the northern provinces, discovered a new bird flu virus branch, symbol 2.3.2 branch. More worryingly, had discovered the virus 2.3.2 branch into 2 groups. With a group of old virus, vaccine against bird flu meets only 75%, while the new virus, vaccines are currently using does not work. Therefore, the risk of spreading the virus in poultry and humans is very large. What is more dangerous than professional bodies continue on raising waterfowl flocks, sold in many places but no signs or symptoms but still carry the virus H5N1.
Dr. Nguyen Hong Ha, deputy director of Tropical Diseases Hospital Central, concerned with the weather hot and humid climate are favorable for growing influenza virus. Moreover, with the normal seasonal flu viruses such as influenza B, H1N1, H3N1, H5N1 ... the risk is present, the virus strains combine or mutate to create new influenza virus virulent more dangerous is huge. Currently, flu vaccines are being used in Vietnam is just common flu as influenza A (H3N1, H3N2, H1N1) and there is no vaccine against A/H5N1 flu in humans.
100% mortality rate
According to Dr. Tran Thanh Duong, deputy director of the Department of Preventive Health (MOH), A/H5N1 flu spread from birds, waterfowl infected with influenza A/H5N1 virus to humans is strongly virulent virus, the mortality rate very high. At this point, the rate of death from influenza A/H5N1 in humans is 100% of cases were detected. Two cases were patients who died despite antiviral treatment.
http://nld.com.vn/20120217102740382p0c1002/virus-h5n1-bien-doi-vacxin-bat-luc.htm
http://www.who.int/influenza/gisrs_labo ... lltree.pdf
The first Vietnamese influenza A (H3N2) from pigs
This is a two-year-old girl, in Duoc, Long An and is now cured. For years, our country has recorded cases of infection with influenza virus A (H3N2) in humans, also known as regular seasonal flu, while flu patients is derived from pigs.
Vietnam H3N2v Swine Flu Case Raises Transparency Concerns
Recombinomics Commentary 13:15
February 15, 2012
The national flu monitoring system detected this case in April 2011. A two-year-old female baby in Long An province contracted the disease and was treated successfully at the Children’s Hospital No 1. in HCM City. The A/H3N2 flu virus she had originated from pigs.
The test results of the HCMC Pasteur Institute were confirmed on January 10, 2012, by the WHO laboratory at the US Centres for Disease Control and Prevention (CDC).
The above comments provide additional clarity on the dates surrounding the confirmed H3N2v case in Vietnam, but still leave many questions unanswered. It is likely that this case was initially classified as seasonal H3N2 in 2011. The H3N2v cluster in Iowa in November led to an alert issued by WHO, largely because the three confirmed cases had no swine exposure. That alert was followed by a media report in Vietnam that described the US cases and increased surveillance in Vietnam. Those reports incorrectly described the US H3N2v cases as H3N1.
Last week media reports in Vietnam again issued a warning about H3N2v cases, but only provided detail on the cases in the United States and again described the cases as H3N1, and a follow-up report claimed no H3N2v cases in Vietnam in 2012 (carefully parsed to avoid acknowledgement of the 2011 case).
Today, reports from Vietnam described the above case (age, gender, and location) and the English language reports clearly indicated this was a 2011 case that was confirmed over a month ago by the US CDC.
This raises several important questions, which have not been answered. None of the reports have cited a swine exposure by the confirmed case. Similarly, the CDC has not released the sequences at GISAID, as was done for the 2011 variant cases in the United States (H3N2v, H1N2v, H1N1v). Moreover, WHO has not announced the confirmed case, in spite of lab confirmation by a WHO regional center, although it is unclear if the WHO has announced this case at its password protected site.
Thus, a month after confirmation, all of the above questions remain unanswered by public data, although the sequence would clearly distinguish between a linkage to Asian or North American swine lineages.
The lack of transparency by WHO and the CDC continues to increase pandemic concerns.
H3N2v Swine Flu Case Confirmed In Long An Vietnam
Recombinomics Commentary 09:15
February 15, 2012
As reported by the National Influenza Center - Pasteur Institute of Ho. Ho Chi Minh, influenza surveillance system key southern countries found cases of A/H3N2 flu originated from pigs.
This is a new 2-year-old female patients in Duoc, Long An influenza have been treated at Children's Hospital 1 and then cured. Samples of these patients have been tested in a laboratory at the CDC standard WHO official - the United States and has been confirmed.
Yang said, this is the first case reported in Vietnam A/H3N2 flu originated from pigs. This slight movement of cases and no evidence of transmission from person to person.
The above translation describe the first case (2F) of H3N2v in Vietnam (Duoc, Long An). In contrast to earlier reports, which described similar cases in the United States, this report describes a PCR confirmed case in the Mekong Delta region in southern Vietnam.
As noted earlier, there are 6 sets of public sequences from H3N2v in swine, isolated in 2010 (A/swine/Binh Duong/03_06/2010, A/swine/Binh Duong/03_08/2010, A/swine/Binh Duong/03_09/2010, A/swine/Binh Duong/03_10/2010, A/swine/Binh Duong/03_13/2010, A/swine/Binh Duong/03_14/2010). All six isolates are closely related and have human H3 and N2 genes, with swine internal genes that are generally more closely related to H3N2v swine sequences in Asia (South Korea and Hong Kong).
However, Hong Kong has released 3 sets of sequences from Guangxi and Hong Kong (A/swine/Guangxi/NS2783/2010, A/swine/Hong Kong/2503/2011, A/swine/Hong Kong/NS2439/2011) , which have similar H3 and N2 human genes surrounding six internal genes from H1N1pdm09. In the United States, all 12 of the H3N2v sequences in humans in 2011 have an H1N1pdm09 M gene. Prior H3N2v cases in the United States have PB1 E618D, which is not in the swine isolates from Vietnam, but is in the new sequences from Hong Kong and China, since E618D is in virtually all H1N1pdm09 PB1 sequences.
The above report does not cite swine contact, so the origin of the infection is far from clear. H3N2v in Vietnam is readily distinguished from H3N2v in the United States.
Information on the constellation of genes in the case in Vietnam would be useful.
US HHS Contracts for H3N2v Vaccine Clinical Trials
Recombinomics Commentary 16:00
January 6, 2012 HHS has contracted with pharmaceutical companies Novartis and Sanofi Pasteur to develop investigational lots of the vaccine. Novartis will produce its supply using cell-culture technology at its plant in Holly Springs, North Carolina, and Sanofi Pasteur will grow the vaccine in chicken eggs (a slower method of production) at its plant in Swiftwater, Pennsylvania.
The influenza virus being targeted is a variant of the A(H3N2) virus found in pigs.
The above comments describe preparations for spring clinical trials for an H3N2v pandemic vaccine. These developments are not a surprise. In August the CDC released sequences of vaccine constructs of A/Minnesota/11/2010, which was followed by a WHO September 29, 2011 report on vaccines, showing that the sera against the above target was effective against the first H3N2pdm11 isolate, A/Indiana/08/2011.
Although December media reports cited the creation of a seed vaccine, the real drivers for the clinical trials were the H3N2pdm11 cluster at the daycare center in Iowa, followed by the trH3N2 sustained cluster in the daycare center in Mineral County, West Virginia (which has a novel N2 which has acquired seasonal polymorphisms via recombination.
The West Virginia cluster was alarming, with 23/70 contacts of the index case exhibiting ILI (influenza-like illness), which led to a CDC request to all states to increase surveillance, especially in children. Multiple states issued advisories or alerts, including Marin County, California, which also cited a new H3N2v case in a Napa county resident in its week 50 report.
Today the CDC published the December 23 early release MMWR, which described the West Virginia cluster, which made it clear that transmission was sustained for a month at the daycare center, but failed to note that 23 contacts had ILI. In December the CDC also held a 50 state conference call.
An explosion of H3N2v cases and clusters is expected this month.
Work Begins on Possible Vaccine Against Novel Flu Bug
- On 05/01/2012
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January 4, 2012 — Taking no chances, the US Centers for Disease Control and Prevention (CDC) is laying the groundwork for a possible vaccine against a novel strain of a swine influenza virus that has surfaced in 5 states and sickened 12 individuals, mostly children, since July 2011, an agency official told Medscape Medical News Tuesday.
The strain, designated A(H3N2)v, is a variant of the A(H3N2) virus that circulates among humans on a seasonal basis. What makes it a variant is a gene from the pandemic 2009 influenza A(H1N1) virus that codes for matrix proteins found in the viral shell.
In Indiana, Pennsylvania, and Maine, the virus appeared to have spread from pigs to humans, according to the CDC. In Iowa and West Virginia, however, the evidence suggests limited human-to-human transmission. In general, the novel virus is no more severe than ordinary seasonal influenza, and all the people infected with it have recovered.
The CDC is encouraging public health agencies and clinicians to collect more nasopharyngeal swabs from patients presenting influenza-like illness for testing to determine whether the novel virus may be spreading on a sustained basis.
CDC spokesperson Thomas Skinner told Medscape Medical News that the agency already has prepared a "seed virus" obtained from A(H3N2)v specimens that drug manufacturers can use to develop a vaccine if needed. Preparing a seed virus involves genetically manipulating specimens to incorporate preferred features.
Because the new virus is different enough from the seasonal viruses now in circulation, the seasonal influenza vaccine for 2011-2012 "is not expected to provide significant protection" against the newcomer, according to a Morbidity and Mortality Weekly Report that the CDC published on December 23. The trivalent seasonal vaccine is formulated to protect against the 2009 pandemic virus, the regular A(H3N2) virus, and an influenza B strain.
CDC Could Be Preparing for 2012-2013 Influenza Season
So far, the evidence does not suggest that the A(H3N2)v strain is spreading freely through communities, which would create the need for a vaccine. The bug could fizzle out, according to Christine Layton, PhD, MPH, a public health researcher and influenza pandemic expert at RTI International in Research Triangle Park, North Carolina.
"There have been past instances where a novel virus comes up and then goes back down," Dr. Layton told Medscape Medical News. "There may be something about the virus that [prevents] sustained human-to-human transmission."
If the A(H3N2)v virus ever takes off, she said, drug manufacturers would have a tough time turning out a corresponding monovalent vaccine "at the drop of a hat." Influenza vaccines are still mass-produced, for the most part, by being grown in chicken eggs. Together with testing and licensing a vaccine, this process easily can last 3 to 4 months.
A more likely scenario, said Dr. Layton, would be incorporating an A(H3N2)v strain in the trivalent seasonal vaccine for 2012-2013, assuming the novel virus becomes that much of a threat. Each February or so, an advisory panel of the US Food and Drug Administration (FDA) recommends 3 strains of influenza that should make up the seasonal vaccine for the coming fall on the basis of what it expects to see circulating then. The CDC then develops the seed viruses for these 3 strains, which the FDA distributes to vaccine makers.
Flu prevention: Vaccine for all seasons
- On 09/12/2011
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As researchers map the stable parts of the proteins that stud the surface of influenza, the decades-long quest for a universal flu vaccine is showing signs of progress.
While the eyes of flu researchers were focused on Asian bird markets in 2009, a pandemic began to emerge at the opposite end of the world in Mexico and California: H1N1 influenza, a version of the 1918 flu virus circulating in pigs for nearly a century, had suddenly leaped back into the human population, which now lacked herd immunity. The virus took the world by surprise.
It took months to develop a vaccine matched to H1N1— too long to thwart the pandemic, which peaked in March 2009 and then again in early November, 2009. “We were fortunate that the virus was not really a nasty bastard and did not kill so many people,” says virologist Robert Webster, whose laboratory at St Jude Children's Research Hospital in Memphis, Tennessee, tracks flu viruses and guides the development of flu vaccines to stop them. “If we had an H5N1 virus that was transmitting from human to human: God help us! We would have run out of antivirals almost overnight.”
The 2009 outbreak reignited the hunt for a universal vaccine. In contrast to the seasonal flu jab or infection, the spreading pandemic virus, because it was so unlike its predecessors, elicited more cross-reactive, broadly neutralizing antibodies than usual — and now scientists had the technology to find them. One patient even managed to make an antibody that could inactivate all 16 subtypes of the influenza type A virus — the so-called FI6 antibody. (Type A influenza is the most virulent kind, and is responsible for virtually all major human flu outbreaks.)
It was, however, a rare find. Antonio Lanzavecchia, an immunologist at the Institute for Research in Biomedicine in Bellinzona, Switzerland, and his colleagues had to screen 104,000 white blood cells (B cells) collected from eight donors until they found one cell that produced the FI6 antibody. FI6 binds to hemagglutinins representative of all the 16 subtypes of type A influenza, including the H1N1 swine flu and avian influenza H5N1, as well as to the more common H3N2 strains. In theory, this FI6 antibody provides a blueprint for designing a one-size-fits-all shot. “People have been searching for it forever,” says Webster. “Now, it looks as if the Holy Grail for flu really might be achievable.”
Steady target
The flu virus can skillfully play a chess-like game with the human immune system. Its surface is packed with varieties of two main proteins: neuraminidase and hemagglutinin. Hemagglutinin in particular plays two vital roles: its stem contains the machinery that allows the virus to fuse with host cells; while flashy loops on its globular head act as decoys. To an antibody, each virus appears to be covered with something resembling a dense tropical forest. The freely moving chains of amino acids through the treetops offer alluring binding sites. But these chains mutate and alter their shapes rapidly. The antibody that the host's immune system tailors to fit into the branches of one virus will be limited to that virus, and not work against any new influenza.
Because existing flu vaccines mimic a natural infection, they fall into the same trap: even if our body manages to make a few broadly neutralizing antibodies they are vastly outnumbered by strain-specific ones that bind to the globular head — and most people have to get a flu shot each year to regain immunity.
To sidestep the trap, the immune system would need to refocus its attack, perhaps onto the bases of the trees: a highly stable region of the hemagglutinin stem that tends to stay the same even after the virus mutates. FI6 and most other cross-reactive antibodies push their way in and go for these hard-to-find targets. “This is the first time that an antibody can neutralize every single influenza virus,” says Rino Rappuoli, head of vaccines research at Swiss pharmaceutical company Novartis. But while calling FI6 a “milestone”, Rappuoli is cautious about seeing it as the key to making a universal vaccine. “That's tough,” he says. “We don't know how to do it yet, but it is a dream that can come true.”
Root of the problem
There are two ways to use broadly reactive antibodies: as a passive immunization to treat severely ill patients who did not respond to antivirals, or as a template to develop a prophylactic vaccine for everyone. The latter is the more difficult task — it requires sophisticated engineering of the antibody to derive a protein that not only fits the antibody's binding site but also manages to coax the human immune system into producing enough ammunition to prevent infection. Many researchers favour starting with the first option. “It's effective, it's extremely broad, and it's human — there should be no problem injecting antibodies into humans,” says Lanzavecchia. “To be frank, our first goal is to use the antibody as a therapeutic.”
Gary Nabel, director of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland, agrees on the difficulty in making a universal preventative flu vaccine. “We've been doing similar work with HIV,” he says. Creating a prophylactic vaccine “sounds simple, but it takes time.” The challenge, then, is in creating a vaccine that will induce this specific yet unnatural response. Even if one presents a specific site of a protein to the immune system, there are many ways in which antibodies can bind to it. “That's clearly an important problem to solve for any infectious disease, and flu can be our poster child,” says Nabel. “When we understand the basics behind this biology we will be in the driver's seat to design a lot of vaccines that could be very, very promising.”
While eliciting 'anti-stem' antibodies in humans is difficult, it is not impossible. Nabel and his team were the first to apply a so-called prime-boost approach in humans to achieve this goal. This technique entails giving a combination of two vaccines administered in sequence to induce the strongest immune response possible against a broad array of influenza strains, including H5N1, H5N2 and H9N2. The priming shot was a DNA vaccine: small, circular pieces of bacterial DNA genetically engineered to code for a specific protein that targets an avian flu hemagglutinin. Then, 24-weeks later, volunteers were given a booster vaccine made of whole inactivated H5N1 virus. This regimen enhanced the immune response against avian flu. In addition, three individuals were able to make broadly neutralizing antibodies directed at the hemagglutinin stem, a result that Nabel says is a “proof of concept” for a universal influenza vaccine.
The mice in microbiologist Peter Palese's lab at Mount Sinai School of Medicine in New York are already protected against various flu strains by experimental, prophylactic flu vaccines. Palese has shown that two truncated versions of hemagglutinin, one with its globular head chopped off and the other only partly expressed, work better than full-length hemagglutinin, but they're not perfect: they offer good protection against H3 strains of influenza virus, but they are weaker against H1. Moreover, Palese echoes the familiar caution from anyone working with animal models: “It's promising,” he says, “but mice are not men”.
Nonetheless, scientists and vaccine companies around the world are hard at work. Advances in high-throughput technology allow them to screen individual B cells from healthy volunteers or patients and search for rare antibodies. In 2008, a group based at the Dutch company Crucell was the first to find broadly neutralizing antibodies against influenza in humans. Apart from exploring therapeutic approaches, they are also trying to vaccinate rodents with conserved viral structures.
Normally, the immune system overlooks the virus's stem (because it's a target that's hard to see and to get to) and produces instead many antibodies that target the viral protein's head. Most broadly neutralizing antibodies, on the other hand, bind to conserved domains on the stem. Crucell is trying to recreate these conserved areas and expose them to the immune system to induce the production of broadly neutralizing antibodies. It's crucial to use the right binding domain, because otherwise the antibody might be just as strain-specific as anything that binds to the head. “We know that we can rebuild the stem in a way that it looks like the binding domain,” explains Crucell immunologist Katarina Radosevic. But the question is how to rebuild these structures in a stable form so that they can induce an immune response in animals. “It's a complex task,” Radosevic says. “You can't just chop off a part of a molecule and expect the rest to fold and function the same way .”
In the pocket
Recently, another target for a universal vaccine was discovered, one that is conserved but does not hide away in the protein folds. At the crown of hemagglutinin's globular head is the receptor-binding pocket, which allows the virus to infect host cells. With minor modifications, this pocket has the same structure on all the 16 subtypes of hemagglutinin. But the pocket is tiny — much smaller than a typical antibody. Nobody expected it to be a good vaccine target, and yet this appears to be the case.
To get snapshots of how the immune system reacts to the seasonal vaccine, researchers from Duke University in Durham, North Carolina, screened antibodies from volunteers several times after vaccination. One of these anti-bodies, dubbed CH65, seemed to be a little more effective than others. The Duke team sent the information to Stephen Harrison, a structural biologist at Harvard Medical School and Children's Hospital in Boston, Massachusetts, for analysis. “We were surprised to find that it docks to the receptor-binding pocket,” says Harrison. “About half of the contacts are with amino acid residues in the pocket itself. The degree and intimacy of mimicry is striking.”
What's more, point mutations in the area surrounding the pocket did not hinder the antibody from docking. When the researchers tested the antibody against 36 strains of H1 that had circulated within the last three decades, it blocked 30 of them. “Over 30 years of evolution of the virus, there were hardly any mutations that had a strong effect on binding,” Harrison says. Another possibility, he adds, is that since 1977, the antibody arose so rarely that the virus did not have to escape its attack.
Harrison's research interest is not so much the creation of a universal flu vaccine as in advancing the basic science of affinity maturation: When exposed to the same antigens time and again, the immune system produces antibodies with slight mutations that will bind much more effectively to the invader. But why do some small changes make such a difference to the immune response — and how can one induce them?
While some scientists are busy mapping the conserved regions on the hemagglutinin molecule, others are still investigating existing vaccine targets that had for many years been the only ones available. These include the ion channel M2, the matrix protein 1 (M1) and the nucleoprotein that the virus needs to keep its genome stable. “We have known about these conserved proteins for at least 20 years,” says Rappuoli. While acknowledging that “theoretically” one might prove to be a good target for a universal vaccine, he says that “there hasn't been much progress” on these fronts.
Many companies are still pursuing these targets. VaxInnate, a biotech company in Cranbury, New Jersey, has engineered a hybrid molecule that consists of four copies of M2e — part of the ion channel M2 that sits on the virus surface — fused into the bacterial protein flagellin. VaxInnate recently reported that its vaccine, called Vax102, safely produces an immune response in humans that should be protective against all strains of influenza A. DynaVax, a biotech company in Berkeley, California, has fused M2e and nucleoprotein to create a vaccine candidate called N895; the goal is to encourage antibodies against M2e as well as T cells against the nucleoprotein. Acambis,the UK biotech company based in Cambridge, now owned by Sanofi Pasteur of Lyon, France, evaluated its own M2e vaccine in a phase I study in 2008 and found that it was immunogenic against influenza A, and well-tolerated. The company also conducted another study that it says showed the vaccine protecting about 70% of ferrets against bird flu.
Further development has stagnated. Sanofi Pasteur is hesitant about moving its M2e vaccine to phase II trials. “M2e alone is unlikely to be better then the current seasonal vaccines,” says Jeffrey Almond, Sanofi's vice president for discovery research and external R&D. “So we stepped back a little and thought about what we could add to M2e. There is no reason why a universal vaccine shouldn't have multiple components.” Meanwhile, Merck, based in New Jersey, has halted its own trials.
A different tack
Another path toward a universal vaccine involves not trying to elicit antibodies, but rather boosting the body's T-cell response to infection. While antibodies prevent the virus from infecting host cells, T cells help to clear the virus from the body by killing flu-infected cells. That's the approach being pursued by vaccin-ologist Sarah Gilbert at the Jenner Institute — a vaccine research organization based at Oxford University in the UK. Gilbert uses an attenuated poxvirus called MVA, which presents the flu nucleoprotein and M1 to the immune system. As a result, Gilbert reports, “we saw a very large peak in T-cell response — everybody improved.” This T-cell-mediated immunity might provide another line of defense against flu, possibly in combination with a protein vaccine that targets the stem of the hemagglutinin. Gilbert invited 11 vaccinated volunteers and 11 non-vaccinated volunteers to a quarantine facility. To test their vaccine, the researchers dripped H3N2 into the noses of their subjects and monitored their flu symptoms as well as their T-cell response.
Combining Gilbert's vaccine with the seasonal flu shot yields a preparation that boosts not only T cells but also the antibody response. Following vaccination with the seasonal flu shot alone, young people respond well by producing antibodies, whereas the same vaccine is less effective in older people. “Using both vaccines together might be extremely useful for vaccinating the elderly,” Gilbert says. Usually, the seasonal flu jabs don't work as well for older people, because their immune response diminishes quickly, and it becomes more and more difficult to make new antibodies as we age. “We boost what people already have,” Gilbert explains. “We are not trying to prime new responses.”
Even a potent universal protein vaccine modelled after the perfect antibody would not change the fact that different age groups react differently to a flu jab. Thus a once-in-a-lifetime shot that protect against all strains might never be achieved for everyone: “The question is what universal means,” says Rappuoli. “Should it cover all the pandemic strains and the seasonal strains? That's almost impossible. But it's OK to have a dream to move forward.”
Source: http://www.nature.com/nature/journal/v480/n7376_supp/full/480S6a.html#f1