The world’s first clinical trial of H1N1 influenza vaccine in pregnant women will be launched this week in the U.S. Pregnant women come under the at-risk category as they are at higher risk of developing severe illness if infected with the influenza virus. Pregnant women will be eligible to receive the vaccine on priority when it becomes available by the end of this month.
According to details available in the Clinicaltrials.gov (a clinical trial registry of the U.S.) site, up to 120 women in the 18 to 39-year age group and who are in their second or third trimester (14 to 34 weeks) of pregnancy will be enrolled in the trial.
The Sanofi Pasteur H1N1 influenza vaccine made from an inactivated virus will be used. Since it is an inactivated virus, the possibility of becoming infected by the virus does not arise. The vaccine will not contain an adjuvant — a substance added to a vaccine to improve the body’s response to vaccine.
The randomised, double-blinded Phase II trial funded by the National Institute of Allergy and Infectious Diseases (NIAID), a government agency, will take place in six medical centres across the U.S. The trial is expected to be completed by July 2010.
The volunteers will receive either 15 micrograms or 30 micrograms of the candidate vaccine. All the volunteers will receive an initial injection and a second injection 21 days later.
The primary objective of the trial is to study the safety of the vaccine in pregnant women. The secondary objective is to assess the immune response after the first dose as well the second dose. The trial will also assess if a single dose will be sufficient to produce the desired immune response. If sufficient immune response is produced after the first dose, the vaccination programme will be restricted to just one shot.
The study will also measure maternal antibodies transferred to the infants through the placenta.
NIAID is planning to conduct additional trials in pregnant women testing candidate 2009 H1N1 influenza vaccines made by other manufacturers.