Europe approves pandemic vaccine; countries must decide own strategies.
The European Commission has approved a new vaccine against the H5N1 bird flu virus — the first vaccine designed to ward off a future pandemic. But how the drug, called Prepandrix, will be deployed by national governments remains unclear.
The vaccine, produced by the UK drug giant GlaxoSmithKline, is aimed at the H5N1 strain currently circulating in birds as epidemiologists think that this is the most likely strain to cause a human pandemic. H5N1, which originated in south-east Asia and is carried by migrating birds and domestic poultry, has caused 382 human cases and 241 deaths worldwide since 2003.
Prepandrix targets an antigen from an H5N1 strain called A/Vietnam/1194/04, which has been detected in birds in Asia, Europe and Africa. Clinical tests have shown that the vaccine is also effective against other closely related variants of H5N1, such as H5N2. The release of the vaccine is seen as a gamble that any future pandemic strain will closely resemble the Vietnamese version used to derive the vaccine.
National governments will now have to choose between two strategies for using the vaccine: stockpile it for use in the event of an outbreak, or initiate a preemptive immunization programme.
These decisions remain the responsibility of Europe's national health authorities. “Many factors must first be considered — [such as] whether to target specific subpopulations, such as healthcare workers or poultry workers, or the whole population,” says virologist Albert Osterhaus of the University of Rotterdam in the Netherlands. Experts expect that a tiny proportion of the population will react adversely to the vaccine. "Whether this is acceptable to people where there is no imminent danger is not so certain,” says Osterhaus.
The first orders for Prepandrix were placed last year by Finland and Switzerland, before it had been approved by the Europea Commission. In 2007, sales for Prepandrix totalled US$284 million worldwide.
In the event of an outbreak, the causative agent first needs to be characterized by researchers so that a vaccine can be designed against that strain. Influenza travels very rapidly, so responding rapidly to control its spread is paramount.
In the event that a pandemic strain differs from that used to make the vaccine, a preemptive vaccination programme with Prepandrix would at least give researchers time to respond to develop a new vaccine.
Recent developments in vaccine production have reduced the response times in vaccine production to a matter of weeks. Andrea Gamotto of the University of Pittsburgh in Pennsylvania, developed a technique to produce a vaccine against H5N1 in less than 36 days (see 'Quick vaccine gets off the starting blocks').
Vaccines and antiviral treatments might not be the only weapons in our armoury. Last month, researchers at the Emory Vaccine Centre in Atlanta, Georgia, and the Oklahoma Medical Research Foundation unveiled a new method to speed up production of human antibodies that could fight back against a virulent virus. The technique, although expensive, could prove useful in responding to future outbreaks.