Early human trial shows encouraging results for H5N1 influenza vaccine

EMBARGO: 00:01H (London time) Thursday May 11, 2006. In North America the embargo lifts at 18:30H ET Wednesday May 10, 2006.

French researchers have found that two-doses of a H5N1 influenza virus vaccine including an adjuvant* can produce a safe immune response in people. They report the results of the phase I clinical trial, involving 300 volunteers, online today (Thursday May 11, 2006) in The Lancet.

Avian influenza A virus H5N1 has caused outbreaks in poultry and migratory birds, and caused death and disease in people. Though the evidence that H5N1 can spread from person-to-person is limited, this subtype represents a potential source of the next pandemic influenza.

Melanie Saville (sanofi pasteur, France) and colleagues assessed whether a H5N1 vaccine, based on a modified strain of the virus, was safe and could produce neutralising antibodies in human beings. In the trial, 300 healthy volunteers received one of six vaccine formulations at various doses with or without an adjuvant (aluminium hydroxide). Participants received two doses of the vaccine on days 0 and 21 and provided blood samples on days 0, 21, and 42. The researchers found that a two-dose regimen of 30 ƒİg (micrograms) of the vaccine induced the highest antibody response after 42 days. All formulations were well tolerated with few severe reactions. The team also found that vaccines given with aluminium hydroxide at 30 ƒİg worked better than those without.

Dr Saville concludes: ¡§A two-dose regimen with an adjuvanted 30 ƒİg inactivated H5N1 vaccine was safe and showed an immune response consistent with European regulatory requirements for licensure of seasonal influenza vaccine.¡¨ However, she adds that the level of post-vaccination antibodies needed to achieve protection against the H5 N1 virus is currently unknown and that with limited manufacturing capacity, low-dose strategies will be the next step.

In an accompanying comment Suryaprakash Sambhara (Centres for Disease Control and Prevention, Atlanta, GA, USA) and Gregory Poland (Mayo Clinic College of Medicine, Rochester, MN, USA) warn that we still do not have a highly immunogenic pandemic influenza vaccine. ¡¨We do not know if these vaccines are sufficient to protect individuals in the event of an influenza pandemic,¡¨ they state. They add that vaccine stockpiling options are also limited because two doses at 30 mg per dose are required, which constrains the number of doses of vaccine possible under existing global manufacturing capacity.


EMBARGO: 00:01H (London time) Thursday May 11, 2006. In North America the embargo lifts at 18:30H ET Wednesday May 10, 2006.

Contact: Dr Melanie Saville, Sanofi Pasteur, Marcy l'Etoile, France. [email protected] via Marielle Bricman T) + 33 4 37 37 70 80

Comment: Dr Suryaprakash Sambhara, Influenza Branch, Mail Stop G16, 1600 Clifton Road, Atlanta, Georgia, 30333, USA. [email protected] via CDC press office T) 404 639 3286

Notes to editors
*An adjuvant is a drug that has few or no pharmacological effect by itself, but may increase the effectiveness or potency of other drugs when given at the same time.

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