Is an effective vaccine already available against the new Influenza A (H1N1) virus?

No, but work is already underway to develop such a vaccine. Influenza vaccines generally contain a dead or weakened form of a circulating virus. The vaccine prepares the body’s immune system to defend against a true infection. For the vaccine to protect as well as possible, the virus in it should match the circulating “wild-type” virus relatively closely. Since this H1N1 virus is new, there is no vaccine currently available made with this particular virus. Making a completely new influenza vaccine can take five to six months.

What implications does the declaration of a pandemic have on influenza vaccine production?

Declaration by WHO of phase 6 of pandemic alert does not by itself automatically translate into a request for vaccine manufacturers to immediately stop production of seasonal influenza vaccine and to start production of a pandemic vaccine. Since seasonal influenza can also cause severe disease, WHO will take several important considerations such as the epidemiology and the severity of the disease when deciding when to formally make recommendations on this matter. In the meantime, WHO will continue to interact 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 during influenza epidemics and pandemics. Other measures include anti-viral drugs, social distancing and personal hygiene.

Will currently available seasonal vaccine confer protection against Influenza A (H1N1)?

The best scientific evidence available today is incomplete but suggests that seasonal vaccines will confer 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 to WHO, 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 the work to develop candidate vaccine viruses. WHO also initiated consultations with vaccine manufacturers worldwide to facilitate the availability of all necessary material to start production of Influenza A (H1N1) vaccine. In parallel, WHO is 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 seasonal vaccine to a Influenza A (H1N1) vaccine yet?

WHO has not recommended stopping production of seasonal influenza vaccine because this 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. Moreover, 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 large-scale vaccine production can start as soon as indicated.

Is it possible that manufacturers 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 pandemic vaccine? Has a vaccine strain been identified, and if so by whom?

A vaccine for the Influenza A (H1N1) virus will be produced using licensed influenza vaccine processes in which the vaccine viruses are grown either in eggs or cells. Candidate vaccine strains have been identified and prepared by the WHO Collaborating Center in Atlanta (The Centers for Disease Control and Prevention (CDC) in the United States of America)1. These strains have now been received by the other WHO Collaborating Centers which have also started preparation of vaccine candidate viruses. Once developed, these strains will be distributed to all interested manufacturers on request. Availability is anticipated by mid-May.