Preliminary analyses of early data from two vaccine trials in the U.S. show the vaccines to be safe and a single dose produces robust immune response within 8 to 10 days after vaccination

The safety of 2009 influenza A(H1N1) vaccines that are undergoing clinical trials in different countries has got a shot in the arm. Fear about the safety of the vaccines, which are being tested on a fast-track mode, was expressed by some doctors in a few countries.

Much like the findings of the two vaccines that are being tested in the U.K. and Australia, preliminary analyses of early data from two vaccine trials in the U.S. showed the vaccines to be safe and immune responses produced to be good.

The preliminary results of the U.K. and Australia trials were published on September 10 in the New England Journal of Medicine journal.

The Director of The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, U.S. has gone on record saying that the vaccines are safe and produced robust immune response in healthy adults in the 18-64 age group.

Another significant outcome seen in the two trails conducted by NIAID is that a single dose of 15 micrograms was able to produce robust immune responses 8 to 10 days after vaccination. More than 2,800 people are participating in the two ongoing trials.

The Sanofi Pasteur vaccine was able to produce a robust immune response in 96 per cent of adults aged 18 to 64 and in 56 per cent of adults aged 65 and older.

In the case of the CSL Limited vaccine, a robust immune response was measured in 80 per cent of adults aged 18 to 64 and in 60 per cent of adults aged 65 and older.

For adults aged 65 and over, the immune response to 2009 H1N1 influenza vaccine was somewhat less robust, as is the case with seasonal influenza vaccines.

According to an NIAID release, information from their studies will help inform the development of recommendations for immunization schedules, including the optimal dosage and number of doses for different age groups.