Vaccines for the new influenza A (H1N1)

Vaccines for the new influenza A (H1N1)
Up-to-date as of 27 May 2009 (Originally posted on 2 May 2009)
Is an effective vaccine against the new influenza A (H1N1) virus already available?
No, but work is already under way to develop such vaccine. Making a completely new influenza vaccine can take five to six months.
What will happen if the influenza A (H1N1) virus changes in the coming months?
There is currently no evidence that the virus has changed since it was first identified, and virus changes are difficult to predict, but laboratories worldwide are monitoring the situation very closely. Should this happen in the coming months, and if the new form of the virus is not very different from the current one, the vaccine will still be effective. If there is a significant change, the vaccine may lose efficacy, so WHO would recommend that the vaccine composition be adjusted.
What implications does the declaration of a pandemic have on influenza vaccine production?
Declaration by WHO of a pandemic alert does not automatically translate into a request for vaccine manufacturers to immediately stop production of seasonal influenza vaccine and start production of a pandemic vaccine. Since seasonal influenza can also cause severe illness, WHO will take several important considerations such as the epidemiology and the severity of the virus when deciding whether and when to make formal recommendations on this matter. WHO will continue to work very closely with regulatory and other agencies and influenza vaccine manufacturers.
How important will influenza A (H1N1) vaccines be for reducing pandemic disease?
Vaccines are one of the most valuable ways to protect people from getting the disease during influenza epidemics and pandemics. Other measures include anti-viral and other drugs, social distancing and personal hygiene.
Will the currently available seasonal vaccine provide protection against influenza A (H1N1)?
The best scientific evidence currently suggests that seasonal influenza vaccines will offer little or no protection against influenza A (H1N1).
What is WHO doing to facilitate production of influenza A (H1N1) vaccines?
As soon as the first human cases of new influenza A (H1N1) infection became known, the WHO Collaborating Center in Atlanta (The Centers for Disease Control and Prevention [CDC] in the United States of America) took immediate action and began work on developing candidate vaccine viruses. WHO also initiated consultations with vaccine manufacturers worldwide to facilitate the availability of all necessary material to start production of a vaccine. WHO is also working with national regulatory authorities to ensure that the new influenza A (H1N1) vaccine will meet all safety criteria and be made available as soon as possible.
Why is WHO not asking vaccine manufacturers to switch production from a seasonal vaccine to an influenza A (H1N1) vaccine?
WHO has not recommended stopping production of seasonal influenza vaccine because seasonal influenza causes 3 million to 5 million cases of severe illness each year, and kills from 250 000 to 500 000 people. Continued immunization against seasonal influenza is therefore important. Given the time that it takes to develop a fast growing candidate vaccine virus, stopping seasonal vaccine production immediately would not allow a pandemic vaccine to be made quicker. At this time, WHO is liaising closely with vaccine manufacturers so that large-scale vaccine production can start as soon as it is required.
Are manufacturers able to produce both seasonal and pandemic vaccines at the same time?
There are several potential options which must be considered based on all available evidence.
What is the process for developing a novel influenza A (H1N1) vaccine? Has a vaccine strain been identified, and if so, by whom?
A pandemic vaccine is, by definition, developed from the pandemic virus. A vaccine for the influenza A (H1N1) virus will be produced using influenza vaccine processes in which the vaccine viruses are grown either in eggs or cells. Vaccine viruses suitable for further development and production are being selected, and are under constant review through the collaborative work of laboratories in the WHO Global Influenza Surveillance Network. These candidate vaccine viruses are being tested in an animal model to verify that they are not pathogenic. They are also available to all interested manufacturers on request. Availability of such vaccine viruses, which is anticipated by late May, will be announced on the WHO website.
In phase 5 of the pandemic alert, will it be necessary to verify the safety of candidate influenza A (H1N1) vaccine viruses in animals (using the so-called "ferret test") prior to the distribution to manufacturers?
There can be no compromise on safety. It will therefore be necessary to test candidate influenza A (H1N1) vaccine viruses in ferrets because it appears that some features of the infection (weight loss and lung pathology) may be more extensive than those seen with seasonal influenza viruses.
How quickly will influenza A (H1N1) vaccines be available?
The first doses of influenza A (H1N1) vaccine could be available within five to six months after identification of the new virus. Prior to this date, small quantities of experimental vaccine will be made available to immunize volunteers in clinical trials to select the best vaccine formulations. Regulatory approval for the vaccines will be conducted by national authorities in parallel with the manufacturing process. National regulatory authorities have put into place expedited processes that do not compromise on the quality and safety of the vaccine. Delays in production could result from poor growth of the virus strain used to make the vaccine.
How would manufacturers be selected?
There are currently more than a dozen influenza vaccine manufacturers with licenses to produce vaccines. Upon request, the vaccine strain will be made available to each of them, as well as to other qualified vaccine manufacturers who are preparing to make influenza A (H1N1) vaccine, but do not yet have a licensed seasonal influenza vaccine.
What is the global manufacturing capacity for a potential influenza A (H1N1) pandemic vaccine? Is this the same as the global manufacturing capacity for H5N1 vaccine?
Projections made for the production capacity of a vaccine for H5N1 cannot be automatically assumed to be the same for an H1N1 vaccine. H5N1 and H1N1 are distinct viruses, so the amount of antigen needed to make an effective H1N1 vaccine may differ from that for H5N1. Therefore, it is not possible to make a precise estimate. However, notwithstanding these considerations, and based on a global survey made by WHO on May 15, 2009, a maximum 4.9 billion could be produced in 12 months. This would only be the case if a number of conditions are met— notably that production yields for influenza A (H1N1) vaccine are equivalent to those usually obtained for seasonal vaccines, and that manufacturers use the vaccine formulation which has been shown for H5N1 influenza as being the most "dose-sparing" (i.e. those which use the smaller quantity of active principle). A more conservative estimate of global capacity is at least 1 to 2 billion doses per year. This does not translate automatically into numbers of persons vaccinated, as we do not yet know how many doses of the vaccine will be needed to achieve protection.
How is the production capacity for influenza vaccines distributed geographically?
Close to 90% of the global capacity today is located in Europe and North America, with further significant manufacturing capacity in Australia and Japan. However, during the past five years, six manufacturers in developing countries have begun to acquire the technology to produce influenza vaccines and have received technical and financial support from WHO.
What is the current WHO recommendation regarding large-scale production of influenza A (H1N1) vaccine?
Based on recommendations from the WHO Strategic Advisory Group of Experts (SAGE), the current production of a Northern hemisphere seasonal vaccine should continue, while WHO should make a recommendation as soon as possible on which virus strain to use for production to enable manufacturers to prepare material to evaluate candidate influenza A (H1N1) vaccines in clinical trials. Implications of not having seasonal vaccine to immunize vulnerable populations, current uncertainty about severity and spread of influenza A (H1N1) virus, and readiness of basic materials were taken under consideration.
What will be the storage requirements for influenza A (H1N1) vaccine?
The vaccine should be stored under refrigerated conditions at between 2°C and 8°C
So far, it has been impossible to develop vaccines for major killers such as HIV and malaria. How sure are we that there will not be scientific or other hurdles in developing an effective influenza A (H1N1) vaccine?
Typically, development of influenza vaccines has not posed a problem. Influenza vaccines have been used in humans for many years and are known to be safe and effective. Effective vaccines are produced each season. However, one key unknown is the yield of vaccine virus production, since some strains grow better than others and the behaviour of the new influenza A (H1N1) strain in manufacturers’ systems is not yet known. New recombinant technologies are under development, but have not yet been approved for use.
Will influenza A (H1N1) vaccines be effective in all population groups?
There are not data on this but there also is no reason to expect that they would not, given current information.
Will the influenza A (H1N1) vaccine be safe?
Licensed vaccines are held to a very high standard of safety. All possible precautions will be taken to ensure safety of new influenza A (H1N1) vaccines.
How can a repeat of the 1976 swine flu vaccine complications (Guillain-Barré syndrome) experienced in the United States of America be avoided?
Guillain-Barré syndrome is an acute disorder of the nervous system. It is observed following a variety of infections, including influenza. Studies suggest that regular seasonal influenza vaccines could be associated with an increased risk of Guillain-Barré syndrome on the order of one to two cases per million vaccinated persons. During the 1976 influenza vaccination campaign, this risk increased to around 10 cases per million vaccinated persons which led to the withdrawal of the vaccine.Influenza A (H1N1) vaccines will be manufactured according to established standards. However, they are new products so there is an inherent risk that they will cause slightly differently reactions in humans. Close monitoring and investigation of all serious adverse events following administration of vaccine is essential. The safety monitoring systems are an integral part of the strategies for the implementation of the new pandemic influenza vaccines. Quality control for the production of influenza vaccines has improved substantially since the 1970s.
Will it be possible to deliver influenza A (H1N1) vaccine simultaneously with other vaccines?
Inactivated influenza vaccine can be given at the same time as other injectable vaccines, but the vaccines should be administered at different injection sites.
Will there be enough influenza A (H1N1) vaccine for everyone?
The estimated time to make enough vaccine to vaccinate the world's population against pandemic influenza will not be known until vaccine manufacturers will have been able to determine how much active ingredient (antigen) is needed to make one dose of effective influenza A (H1N1) vaccine and whether 1 or 2 doses are needed to protect one person.In the past two years, influenza vaccine production capacity has increased sharply thanks to expansion of production facilities as well as advances in research, including the discovery and use of adjuvants. Adjuvants are substances added to a vaccine to make it more effective, thus conserving the active ingredient (antigen).
What is WHO's perspective on fairness and equity for vaccine availability?
The WHO Director-General has called for international solidarity in the response to the current situation. WHO regards the goal of ensuring fair and equitable access by all countries to response measures to be among the highest priorities. WHO has requested manufacturers set aside future influenza A (H1N1) vaccines for United Nations agency procurement. In addition, donations are expected from countries holding advance purchase agreements for influenza A (H1N1) vaccine, and tiered-pricing arrangements will be discussed with the vaccine manufacturing industry in order to make vaccines more affordable for developing countries.
Who is likely to receive priority for vaccination with a future influenza A (H1N1) vaccine?
This decision is made by national authorities. As guidance, WHO will be tracking the evolution of the pandemic in real-time and making its findings public. As information becomes available, it may be possible to better define high-risk groups and to target those groups for vaccination, thus ensuring that limited supplies are used to greatest effect.
Will WHO be conducting mass influenza A (H1N1) vaccination campaigns?
No. National authorities will implement vaccination campaigns according to their national pandemic preparedness plans. WHO is exploring whether the vaccine can be packaged, for example, in multi-dose vials, to facilitate the rapid and efficient vaccination of large numbers of people.
How feasible will it be to immunize large numbers of people in developing countries against a pandemic virus?
Developing countries have considerable strategic and practical experience in delivering vaccines in mass campaigns. The main issue is not feasibility, but how to ensure timely access to adequate quantities of vaccine.
What is the estimated global number of doses of seasonal vaccine used annually?
The current annual demand is less than 500 million doses per year.
Will seasonal influenza vaccine continue to be available?
At this time there is no recommendation to stop production of seasonal influenza vaccine, and manufacturers are actively working to finish the ongoing production for Northern hemisphere 2009-2010 seasonal influenza vaccine.
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