A VACCINE SUITABLE FOR USE AGAINST THE NEXT INFLUENZA A PANDEMIA

This invention relates to a vaccine and a method of vaccination against influenza A virus. Said vaccine and method of vaccination are suited for protecting humans against the 'human avian flu virus' which is a human-to-human transmitted recombinant (hybrid) virus arising from a dreaded recombination (union of the genes of two or more different viruses) of an influenza A virus so far only found in birds and limited to bird-to-bird transmission. Such a virus is expected to cause the next global epidemic, i.e. pandemic, of influenza A, possibly facing mankind in the not too distant future. There have already been some cases of bird-transmitted illness in humans, but the virus has so far been unable to spread from one person to another.

Influenza A disease is, in both humans and animals, caused by type A influenza virus which is depicted in Figure 1.

The virus contains a ribonucleoprotein (RNP) consisting of eight single RNA strands combined to nucleoproteins (NP) and polymerase proteins (P1 _f P2, P3). The core is surrounded by a layer of matrix (M) protein with a molecular weight (MW) of 26000. The envelope consists of a lipid bilayer through which the antigenic viral glycoproteins, haemagglutinin (HA) and neuraminidase (MW 58000), project. Haemagglutinin is composed of two polypeptides, HA1 (MW 50000) and HA2 (MW 25000).

Among humans, influenza A is transmitted either by direct droplet infection or other form of contact with respiratory secretions. The incubation period is very short, from one to a few days. The virus multiplies in the ciliated epithelium of the respiratory tract, destroying it. Influenza A infection (infection = invasion of the body by a pathogenic agent) is followed by a relatively brief period of immunity during which the same virus type is unable to cause a new infection and illness.

The numerous different influenza A viruses isolated during various epidemics ove the years share the following structural features: They are 80 to 120 nanometres in diameter, spherical in shape (above) or sometimes in the form of long filaments Through the fatty envelope of the virus protrude antenna-like processes with which the virus attaches to its target cell, infecting it. These processes, known as viral surface proteins, comprise: (1) two-domain haemagglutinin (H antigen) and (2) neuraminidase (N antigen). Thus, there are two of these sites, or antigens, which trigger antibody production in the body, on the surface of the influenza A virus (an 'antigen' is the biochemical structure that the immune defence system of the infected individual recognises as foreign thereby activating antibody production in the individual). It is these two antigens, H and N, which determine the type of the virus. The protein structure of these antigens in turn depends on the RNA sequences, i.e. the viral genome, inside the envelope of the virus. Of the various influenza viruses (there are B and C influenza viruses in addition to the influenza A virus), the influenza A virus is clearly the most important human pathogen, and its antigens also display most structural variation. The extensive changes in antigen structure (antigenic shift) associated with the emergence of new types of the same virus species probably result from genetic recombination, meaning that two different virus types exchange genes and consequently also their H and N antigens. When chicken embryos are infected with two different influenza A viruses, about 10% of the progeny are genetic recombinants having the H and N antigens of both their 'parents'. In most other viruses, the corresponding recombination rate is less than 1%. The high recombination rate found not only in animal influenza A viruses but also in human influenza A virus is due to the fact that the viral genome (the RNA inside the envelope of the virus that encodes the amino acid sequence of the viral proteins, including that of the H and N antigens) consists of several segments. During co-infection (a situation in which two different viruses enter the body at the same time), pieces of RNA from different viruses easily end up inside the same virus, and these pieces then encode their characteristic H and N antigens.

All influenza A viruses share a common S antigen underneath the viral envelope, providing the basis for designating them influenza A viruses. According to the structures of their H and N surface antigens, influenza A viruses are divided,

among others, into the following types expressly capable of having caused a pandemic (Table 1 below):

Table 1

Emergence of new pandemic influenza A virus types

H antigen N antigen Year

HO N1 1934

H1 N1 1947

H2 N2 1957 'Asian flu'

H3 N2 1968 ηong Kong flu'

As seen in the table above, new pandemic types have emerged at roughly ten-year intervals, apart from the long pause that has prevailed since 1968.

Influenza pandemics are known to have occurred at least from the 12th century onwards. On the basis of clinical and epidemiological data, it can be stated with fair certainty that these early pandemics were indeed caused by influenza A virus. There have been several pandemics per century, some of them associated with particularly high mortality.

Pandemics with a high mortality rate include the outbreaks of 1889-1895 and

1918-1919. The latter, known as the Spanish flu, had a mortality rate of 6-8% and claimed the lives of at least 20 million people. The victims of the Spanish flu included many young and previously healthy people.

The H2N2 type ('Asian flu'), which emerged in 1957, was first isolated in China. Within six months, it swept the globe causing epidemics which affected 20-40% of the population.

A pandemic was also produced by the H3N2 type ('Hong Kong flu ¹ ) after its appearance in 1968.

Thus, a major change in the H antigen, ¹ H antigen shift ¹ (with the N antigen remaining unchanged) has been sufficient to generate a pandemic.

The underlying reasons for the regular recurrence of influenza epidemics each winter are the appearance of ever new subtypes, or virus variants (the term varian in this context means modification within a single virus type without any part of another virus type being transferred into it), and the limited period of immunity afforded by infection or vaccination. The small antigenic changes within a certain type, i.e. the development of variants, enhance the potential of the virus to reproduce and cause disease. The emergence of a new type or variant usually leads to the disappearance of corresponding previous types or variants. It is conceivable, however, that old types or variants may later reappear. Analyses of blood sera of people who lived in the late 1800s have yielded indications that the causative agent of the pandemic of that time was closely related to the H2N2 Asian type of 1957. Even the reappearance of, say, a HON 1 type of virus as a cause of epidemics cannot, therefore, be ruled out.

There are lots of small antigenic differences among virus strains of the same type. For instance, a large number of H3N2 variants have been identified. Such antigenic drift is believed to be due to mutations of viral RNA.

Influenza A viruses have been isolated not only from humans but also from birds, horses, swine and dogs, for instance. The antigen structure of animal influenza A viruses is also highly variable. For example, 10 types of H antigen and 6 types of N antigen have been found in avian (including chicken, duck, turkey) A viruses. It seems that human influenza A viruses can be transmitted to animals, in which (a) a genetic recombination with animal influenza A virus takes place. New hybrid viruses arising as a result of the recombination can then return to cause disease in mankind. On the other hand, (b) genetic recombination can equally well take place in a human individual with two simultaneous influenza A infections.

In the case of 'avian flu vims', that is, the H5N1 type of influenza A virus which originally spread from wild birds to domestic fowl, we are most probably seeing a sequence of events compatible with point (a) above. The disease was transmitted from birds to humans for the first time in Hong Kong in 1999, followed by new cases in Vietnam in 2003. By November 2005, about 100 new cases of disease transmitted from poultry to humans had been reported in South-East Asia, half of them fatal. Fortunately, the H5N1 'avian flu virus' has not been able to spread from one person to another.

Upon entering the human body, the H and N antigens of influenza A virus activate the body's immune defence system, and white blood cells start to secrete antibodies into body fluids. These proteins are capable of exactly recognising the virus from its H and N antigens and then destroying it with the help of white blood cells. This is the basis of vaccination against influenza A virus.

The principle of influenza vaccination is simple: The vaccine contains small amounts of H and N antigen (but not necessarily other parts of the virus). After entering the body through vaccination, these antigens trigger the production of antibodies which then prevent a subsequent influenza A virus from infecting the body. The resulting immunity is usually of the order of 70%. In other words, vaccination provides protection against infection and disease in seven out of ten cases, on average.

For example, the vaccine to be used in Finland with respect to an epidemic in the 2005-2006 winter season consists of the A/Fujian/411/2002 (H3N2) antigen combination and the A/New Caledonia/20/99 (H1N1) antigen combination. The WHO recommends that this vaccine also be used in the southern hemisphere for the epidemic in the 2005 winter season but that the northern hemisphere in winter 2005-2006 should use a vaccine composed of the antigen pairs A/California/7/2004 (H3N2) and A/New Caledonia/20/99 (H1 N1).

Said antigen nomenclature stems from the fact that, as mentioned above, the virus type possessing the H3N2 surface antigens in particular comprises several subtypes, or variants, and such names allow the identified subtypes to be

distinguished from one another. The classification and nomenclature of influenza A viruses is based on a recommendation made by the WHO in 1971, according tc which a virus can be named, for instance, as follows:

Influenza A/Finland/4/68 (H3N2). The word influenza is followed by virus type, place of isolation, isolate number issued by the laboratory/year of isolation and the types of H and N antigens in parentheses.

Second example: Influenza A/Turkey/Canada/26/66 (Hav5Neq2). Turkey' denotes that the virus was isolated from turkeys. Its H antigen is of avian (bird) type 5, and the N antigen is of equine (horse) type 2.

Third example: Influenza A/England/1/51 (H1) " A/Hong Kong/1/68 (N2). This relates to a laboratory-produced recombinant variant with an H antigen originating from the A/England/1/51 (H1N1) strain and an N antigen from the A/Hong Kong/1/68 (H3N2) strain. This is one of the first variants used in influenza A vaccines.

In Finland, the following variants have been used as vaccines since 2000 and up to 2005 (Table 2):

Table 2

Winter 2000-2001: A/Sydney/5/97 (H3N2) - A/Beijing/262/95 (H1N1) Winter 2001-2002: A/Moscow/10/99 (H3N2) - A/New Caledonia/20/99 (H1N1) Winter 2002-2003: A/Moscow/10/99 (H3N2) - A/New Caledonia/20/99 (H1N1) Winter 2003-2004: A/Moscow/10/99 (H3N2) - A/New Caledonia/20/99 (H1N1) Winter 2004-2005: A/Moscow/10/99 (H3N2) - A/New Caledonia/20/99 (H1N1) and as mentioned above: Winter 2005-2006: A/Fujian/411/2002 (H3N2) - A/New Caledonia/20/99 (H1 N1)

The subtype causing the next epidemic is never exactly the same as the variant that caused the previous epidemic. Hence, a vaccine does not provide absolute protection.

The more the particular new variant differs from the previous one, the less protection does the vaccine provide. This, in turn, is due to the body not simply producing one antibody against each of the two surface antigens but there being in both the H and N antigen many different chemical structures each of which ma^ trigger the production of an antibody specific to it. These sites are known as epitopes. In case the epitopes' ability to trigger antibody production is a weak one it will be easier for the virus to invade the body and multiply, causing disease.

In commercial vaccines used so far (Begrivac®, Flupar®, Fluzone®, Influvac®, Vaxigrip®, etc.), antigen H and antigen N are contained in the same vaccine, which is why these vaccines might be best called 'pair-antigen vaccines', 'antigen pair vaccines ¹ or 'diantigen vaccines'. As these designations are not in general use, however, the designation 'HN antigen pair' or 'antigen pair HN' will be used in the current text regardless of whether said antigens are derived from the same virus strain or different strains. And 'monovalent' influenza A vaccine denotes a vaccine directed against a single viral strain. The aforementioned commercially used vaccines are divalent with respect to the HN antigen pair, containing the antigen pairs H3N2 and H1N1. The alternative to a monovalent vaccine containing different pairs of HN antigens is a vaccine containing a single H antigen or a single N antigen. Nevertheless, the latter type of vaccine is known to be immunologically less effective than vaccines based on the HN antigen pair since both the H and N antigen is independently capable of triggering the production of antibodies.

Vaccine development targeting an anticipated future epidemic will of course pursue a vaccine in which the antigenic structures correspond as comprehensively as possible to the antigenic structures, i.e. epitopes, of the virus variant causing the forthcoming epidemic. This can, strictly speaking, never be fully realised, as the causative agent of an influenza epidemic is in practice always 'one step ahead ¹ of the vaccine. Thus, for reasonable prevention of epidemics, mass vaccinations against influenza have to be carried out using in-advance produced vaccines which do not contain the exact antigenic variant causing the epidemic and which therefore only yield 70% protection against the disease: Since influenza epidemics in the world occur in wintertime, and winter in the northern hemisphere coincides with summer in the southern hemisphere, and vice versa, two annual vaccination

programmes at six-month intervals are required to immunise the populations of both hemispheres. In practice, mass vaccinations against influenza have to be carried out using a vaccine prepared against the HN antigen of the virus strain tha caused the most recently ended epidemic in that particular hemisphere, which means that these vaccinations take place 12 months after the 'previous vaccination round'. Hence, to make it in time, the new vaccinations must be done using an 'outdated' vaccine, that is, a vaccine prepared against the HN antigen combination of the year before. The vaccine is at best 'last year's vintage' but, as is apparent in Table 2 on page 4, sometimes the same combination of vaccine antigens has been used for several years in a row, e.g. in Finland. Table 2 also shows that the vaccines contain, in addition to the HN antigen pair (H3N2) of the virus that caused the epidemic of the previous year, the HN antigen pair (H1N1) of a virus that has caused epidemics further back in time.

The H5N1 avian flu virus is most likely to undergo recombination over time into a new type of virus which can infect humans and is also capable of human-to-human transmission and potentially able to cause a pandemic. Apart from the fact that the time of occurrence of an anticipated pandemic is of course unknown, the development of a vaccine against it is also hampered by a lack of well-grounded predictions about the antigenic type of the future pandemic virus.

A vaccine containing the antigen pair Hav5Nav1 has already been invented (e.g. Chinese patent no. CN1624116), developed and introduced (CSIRO Livestock Industries, Dickson, Australia) for vaccinating birds against H5N1 bird flu. Extensive vaccinations of poultry with this vaccine have recently been started in countries where cases of transmission to humans have occurred. Previously, the only effective means was to destroy millions of poultry. In spite of poultry vaccinations, wild birds from which the disease originally came from will undoubtedly continue to spread the disease.

Corresponding H5N1 vaccines for humans (known as 'prototype vaccines') have also been developed (WHO) using the following antigenic types: A/Hong Kong/213/2003, A/Vietnam/1194/2004 and Aλ/ietnam/1203/2004. Nevertheless, the disease has such low contagiousness in humans that there has been no point

in vaccinating people with these vaccines. Yet many countries of the world, including Finland, are planning to procure large quantities of prototype vaccine, reasoning that vaccination with a prototype vaccine in the event of a pandemic might afford citizens some protection against the disease. This is only valid in case the pandemic is caused by a H5N1 type of virus. The current prototype vaccine is not effective against new variants of H5N1 virus, however, which make it necessary to produce new batches of prototype vaccine when such variants emerge.

Regarding a human-to-human transmissible pandemic virus derived through recombination (antigenic shift), the type of such virus is so far unknown but its surface antigens will not be of the H5N1 type. This means that the 'prototype vaccines' against the feared pandemic that have been developed so far can by no means be effective against such a novel virus type, and the same applies to any H5N1 prototype vaccine developed in the future.

As to the HN antigenic type of the actual human-to-human transmissible virus causing the future influenza A pandemic, no one has ventured to present rational predictions in public even about its conceivable HN antigenic type. In the absence of such information, it has, of course, been impossible to embark upon systematic development of a pandemic vaccine. Consequently, it seems that a pandemic outbreak in the present circumstances would cause enormous destruction before a specific vaccine against the causative virus type can be developed and introduced.

Constructively planned development of an effective 'human avian flu vaccine' before the emergence of the next influenza A pandemic seems impossible, considering the number of different HN antigen pairs in human and animal viruses so far identified and taking into account their potential recombinations:

As mentioned above, 10 different H antigens and 6 different N antigens have been found in birds. In humans, 6 different H antigens and 3 different N antigens have been found.

Hence, a total of 16 H antigens (H1-H16) and 9 N antigens (N1-N9) are known in humans and birds. It follows that the number of potential (re)combinations of thes antigens is 16 (10 + 6) x 9 (6 + 3) = 144. Co-administration of all these HN antigei pairs in the same vaccine ('polyvalent pan-vaccine ¹ = a vaccine containing all known influenza A antigens) is obviously a practical impossibility. If it were desirec to include all known subtypes, i.e. variants, in this same vaccine, the number of different possible combinations would be huge. If instead of a vaccine containing all possible pairs of HN antigens, a corresponding vaccine only consisting of all possible individual H and N antigens were used, a much lower figure would be obtained: 10 + 6 + 6 + 3 = 25. With both of the pan-vaccine types described, all the antigens would be administered in the same vaccine suspension. This is a Utopian idea in terms of practical vaccine development.

Patent document no. WO 2005/107797 A1 presents a vaccine to prevent the effects of an influenza A pandemic without knowledge of the antigenic type of the future pandemic virus. The document offers as an inventive embodiment i.a. a vaccine containing antigens isolated from both avian and human pathogenic influenza A strains (WO 2005/107797 A1: page 5: lines 24-28).

It has become evident above in the present application that the different combinations required for vaccine formulations containing H and N antigens, either pairwise or individually, are almost limitless in case the subtypes of the viral antigens are also accounted for, as indeed they should be. The embodiment presented in document no. WO 2005/107797 A1 limits the avian antigens and antigen pairs to those H antigens and corresponding types of HN antigen pairs which show high pathogenicity in birds (HPAI), and recommends that the H and N antigens contained in one of the current regular vaccines be used as the human influenza A antigens according to the invention.

It is known for certain that of the many possible (re)combinations of antigens, the next influenza A pandemic will be caused by a virus possessing just one particular HN antigen pair and, furthermore, that one single vaccine only, containing precisely these particular H and N antigens, will be effective against it. If the idea presented as inventive in document no. WO 2005107797 were to receive patent

protection, and a pandemic were later on caused by any one HN virus type included among the antigen combinations within the scope of the invention, pater protection would apply not only to a vaccine of this antigenic type but also to a large number of other vaccines which, according to the invention, prevent a pandemic and include in their compositions the numerous other antigens and the combinations in accordance with the invention. Yet, said vaccines would be ineffective. This reveals the important fact that the embodiments of the invention are no longer meant to be applied in a situation where a pandemic virus has already emerged and its HN antigenic type is known. Therefore, should a professional person wish to utilise the invention in question and prepare a vaccine providing protection against a future influenza A pandemic, they would need to use concomitantly in a single vaccination (i.e. in generating an immune response against the potential types of pandemic virus addressed in the invention) all the antigens within the scope of the invention, since they would not know which particular HN antigen pair among the HN antigen pairs within the scope of the invention would be causing the pandemic. On these grounds, it is obvious that a vaccine in accordance with the invention presented in document no. WO 2005/107797 A1, containing all the antigens within the scope of the invention, or vaccinating separately with each of these antigens is impossible to implement in practice.

Hence, in reality we are facing a situation where humanity, including the vaccine industry, is forced to stand On the razor's edge ¹ waiting for the appearance of an influenza A type causing 'human avian flu', followed by isolation of its H and N antigens and subsequently the time-consuming process of developing a strain-specific vaccine and making it available to the public. Unfortunately, however, an incipient epidemic is most likely able to develop into an uncontrolled pandemic during the time spent on developing, producing and distributing the vaccine. In the lengthy process of vaccine production, isolation of a virus with the right antigenic type is followed by culturing and propagating the virus in chicken eggs or mammalian cell culture. The virus cultures are then inactivated and their surface antigens harvested. The antigens are then isolated, purified and formulated into a vaccine. After packaging and distribution, the vaccine is finally ready for use.

.

On the whole, what we dealing with is, therefore, a threat of a very serious influenza A pandemic affecting the world's population, with no concrete prophylactic means having been so far discovered in the form of a vaccine likely t be effective in the prevention of the pandemic.

The present invention contributes substantially to addressing the aforementioned problems.

The principle of the present invention is as follows:

As it is known that the virus causing a potential pandemic will evolve from the H5N1 type of avian flu virus, it is possible even in the absence of information about the form of the future 'pandemic virus' ('human avian flu virus') to conclude a few relevant facts regarding the type of the future pandemic virus (cf. Table 1):

1) It is known from before that replacement of an H antigen by another H type antigen, with the N antigen remaining unchanged, is sufficient to unleash a pandemic.

2) By analogy, all that may be required for the outbreak of a pandemic is the replacement of an N antigen by another, with the H antigen remaining unchanged.

3) It is probable that the pandemic virus will develop through recombination of N and H antigens in a co-infected person or bird.

The closest possible recombinants would be of type H4N2, H6N2 or H5N2.

Preparing a human vaccine against virus types possessing the antigen combinations H4N2 and/or H6N2 is not justified, as these virus types have already been isolated from birds and are known to be harmless to humans. A few cases of H4N2-related illness, albeit mild, have been encountered in humans. Type H6N2 is not found in humans and only causes a mild disease in birds (Halvorson D.A. et al. 2002, Webby RJ. et al. 2003).

Of the above-mentioned three antigenic types, the one remaining, H5N2, is knowi to have been devastating for poultry. Fortunately, there have as yet been no instances of human disease caused by it.

This virus type, H5N2, was first isolated from birds in the USA in 1983-1984, then in Mexico in 1992-1995 and again in the USA in 2004. It caused serious epidemics in domestic fowl. The epidemics were brought under control by slaughtering millions of birds and finally by developing an H5N2 avian type vaccine against the disease (Garcia A. et al. 1998).

The currently occurring dreaded 'avian flu' type of virus, H5N1 , which is capable oi infecting humans, was previously isolated from birds in England in 1991 but it was not until 1997 in Hong Kong that the virus evidently acquired the ability to spread from birds to humans. The H5N1 type resurfaced in Vietnam in 2003 and has so far infected more than one hundred people, killing approximately half of them. Migratory birds have already spread the virus as far as Europe. All human infections have taken place in South-East Asia, however. This variant of the H5N1 virus must either be a variant of the England 1991 type (antigenic drift), with no major alteration in H and/or N antigens, or alternatively a new H5N1 antigen combination formed through recombination (antigenic shift). The latter option appears more likely judging, for instance, by the several-year interval between the first and second appearance of the virus type.

The N (human) 2 antigen is currently circulating in the world in several variants that are readily transmitted from person to person. These variants have in recent years occurred and still occur in combination with the H (human) 3 antigen (i.e. various H3N2 variants causing recent epidemics in humans). This is very worrisome since the N (human) 2 antigen becomes at once a great threat if genetic recombination causes it to unite with the H (avian-human) 5 antigen, resulting in a hybrid virus e.g. of type AA/ietnam/1203/2004 (H5) - A/California/7/2004 (N2).

A H3N2 type of vaccine composed of the N2 antigen together with the H3 antigen and also containing the H1N1 antigen pair as a suspension in the same injection

ampoule has been used for decades to prevent annual epidemics in both hemispheres, and it is self-evident that this type of vaccine will continue to be used for epidemic prevention at least until the next pandemic breaks out. As mentioned above, vaccines have been developed against the H5N1 type of virus: a vaccine containing the Hav5Nav1 antigen pair for use in poultry and an injectable vaccine containing the Hav-human5Nav-human1 antigen pair for use in humans ('prototype vaccine ¹ ). Prior to this, an injectable vaccine (Hav5Nav2) had also been prepared against the H5N2 type of virus, but only for use in poultry, as evidenced by the abbreviation.

It is clear that none of the above-mentioned vaccines will be effective against a recombination-derived future pandemic virus, 'human avian flu virus', which will most likely be of type H5N2 (Hav-human5Nhuman2) (cf. above-cited example: A/Vietnam/1203/2004 (H5) - A/California/7/2004 (N2)).

Since vaccination against influenza A is based on antibody production triggered b\ H and N antigens, a vaccine against the probable pandemic virus type, H5N2, can nevertheless be obtained by combining these very vaccines containing the H3N2 and H5N1 antigens. Vaccinations are started immediately after the appearance of the first verified cases of human-to-human transmitted disease. To elicit an immune response against the H5N2 virus type, vaccination is carried out by combining into a single vaccination those H3N2 and H5N1 antigenic variants of the virus most recently used in the world.

This unexpected and surprising finding constitutes the present invention.

Compared with previously known options for preventing an influenza pandemic, the two explicitly and precisely defined vaccines or a vaccine formulation combining these two, in accordance with the present invention, afford the following significant benefits compared with prior art:

- Production of the components of the vaccine is prior art, and these components have already been industrially produced.

- There are already stores of the vaccine components, and more of them can be rapidly produced.

- The vaccine is available for use immediately upon observation of an epidemic/pandemic outbreak.

If instead of an embodiment of the present invention it were desired to use prior art in preparing a vaccine against a future type of human avian flu virus and to introduce this vaccine, one would first have to wait until a human-to-human transmissible disease breaks out, the virus is isolated and its antigens determined and the vaccine is grown, isolated, purified, tested, packed and distributed.

In accordance with the invention, measures to protect against a pandemic can be undertaken as soon as the first significant human-to-human transmissions of H5N2 virus are verified. By using a combination of the most recently used variant of the H3N2 virus vaccine and of the most recently used variant of the H5N1 virus vaccine, both of which are continuously available on the world market, the time saving amounts at least to the time that would be spent on developing and distributing a strain-specific vaccine. In the best case, an embodiment in accordance with the present invention can be used to avoid a pandemic altogether, as the most critical phase regarding its outbreak is precisely the delay caused by the development and introduction of a strain-specific vaccine.

The present invention is characterised by what is stated in the characterising parts of the patent claims.

Exemplifying practical embodiments of the present invention:

Example 1

Single-use influenza A vaccine suspension for intramuscular or subcutaneous injection in humans is prepared as follows: Influenza A virus of surface antigenic type Hhuman3Nhuman2 (H3N2) and influenza A virus of surface antigenic type Hav-human5Nav-human1 (H5N1) are grown and propagated for instance in

accordance with British patent no. GB1183506 by injecting the virus into fertilisec chicken eggs or mammalian cell cultures. After culturing, the viruses are purified by differential centrifugation and then inactivated with diethyl ether or diethyl acetate at +0 ... +5° C. Their surface antigens are isolated, purified, quantified an qualified, and the diantigens are mixed in the vaccine suspension. The finished suspension is filled in 0.5-1.0 ml injection ampoules with the amount of diantigen in this dose of suspension being 5-250 microgrammes of the former type and likewise 5-250 microgrammes of the latter type. The vaccine can then be injected subcutaneously or intramuscularly, with adherence to the shelf life of the preparation which is 12 mo. at +2 ....+8° C.

An alternative way of arousing the body's immune response (vaccinating) against H5N2 virus by combining the vaccines into the same suspension and injecting this suspension is to inject the two, that is, both the H3N2 antigen-containing vaccine and the H5N1 antigen-containing vaccine, separately within a reasonable time span, preferably at the same vaccination occasion.

Example 2

An already existing, generally available vaccine suspension for preventive influenza vaccination of humans in the 2005-2006 season, made of influenza A viruses of H3N2 type and H1N1 type, and an already existing vaccine suspension containing surface antigens of influenza A virus of Hav-human5Nav-human1 (H5N1) type (prototype vaccine) are combined in the ratio 1:1 and then filled in the same 0.5-1.0 ml injection ampoule, with the amount of each diantigen being 15 microgrammes per injection ampoule. (The vaccine also contains an antigen against influenza B virus, as is customary in H3N2 - H1N1 diantigen vaccines. Its amount is likewise 15 microgrammes/vaccine dose.) The vaccine can then be injected subcutaneously or intramuscularly, with adherence to the shelf life of the preparation which is 12 mo. at +2 ... +8° C.

An alternative way of arousing the body's immune response (vaccinating) against H5N2 virus by combining the vaccines into the same suspension and injecting this suspension is to inject the two, that is, both the H3N2 antigen-containing vaccine

and the H5N1 antigen-containing vaccine, separately within a reasonable time interval, preferably at the same vaccination occasion.

Example 3

An effective dose of an H3N2 type of vaccine preparation for administration to human nasal mucosa via the nostrils, produced for instance according to Russian patent no. RU2159812, is administered intranasally, and at the same time an effective dose of an H5N2 (prototype) vaccine for humans, produced in a corresponding manner, is likewise administered through the nose, or an effective injectable dose of prototype vaccine in accordance with Examples 1 and 2 is administered subcutaneously or intramuscularly.

Example 4

In accordance with the present invention and Examples 1-3, if cases of H5N2 disease were encountered in humans for instance in the northern hemisphere in winter 2005-2006, the vaccine A/Califomia/7/2004 (H3N2) - A/New Caledonia/20/99 (H1N1) would be combined with the A/Vietnam/1203/2004 (H5N1) prototype vaccine. This is a rapid way of protecting people against H5N2 virus since the vaccine components already exist and they are easy to combine.

Example 5

A more preferred vaccine composition, compared with the above vaccine in Example 4, could be constructed in accordance with the present invention by replacing in the above vaccine composition the A/New Caledonia/20/99 (H1N1) antigen pair (which is in this case redundant) by the A/Fujian/411/2002 (H3N2) antigen pair. In terms of antigen pairs, the vaccine would hence be of the form A/California/7/2004 (H3N2) - A/Fujian/411/2002 (H3N2) - A/Vietnam/1203/2004 (H5N1). It would provide comprehensive protection for the populations of both the northern and southern hemispheres in the event of the recombination into a H5N2 virus taking place for instance in winter 2005-2006, as discussed above.

REFERENCES CITED

Patent documents:

GB1183506 CN 1624116 RU2159812 WO 2005/107797 A1

Other references:

Halvorson D.A. et al. 25 years of avian influenza in Minnesota; College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Avenue, Saint Paul, Minnesota 55108, U.S.A.

Webby R.J. et al. Multiple genotypes of non-pathogenic H6N2 influenza viruses isolated from chickens in California; Avian Dis. 2003; 47(3 Suppl): 905-10.

Garcia A. et al. Efficacy of inactivated H5N2 influenza vaccines against lethal A/Chicken/Queretaro/19/95 infection; Avian Dis. 1998 Apr-Jun; 42(2): 248-56.