A shot of H1N1 vaccine enough to stave off virus

Scientists not sure of immunity endurance

The study -carried out by UK's University of Leicester and Leicester Hospitals in 100 healthy volunteers between 18 and 50 years-- shows that a single shot is enough to induce a strong immune response.

"Two doses do give higher levels of antibody but one dose of MF-59 adjuvanted vaccine is sufficient," Iain Stephenson, leader of the vaccine trial team, at the Leicester Royal Infirmary told Deccan Herald.

However, the vaccine's efficacy in children and the elderly, who are considered high-risk groups, is not yet known. Scientists are also not sure how long the protection would last.
Novartis, who manufacture the vaccine, is one of the two pharmaceutical giants that responded positively to India's request of making H1N1 vaccine available after conducting a bridging study on a few hundred individuals.

"We tested in 18-50 yr old healthy adults and must wait for studies in children and elderly people," Stephenson said. Asked how long the vaccine can protect an individual against H1N1, he said, "This is unknown at present. We report only responses at day 21 after vaccination."The trial evaluated the vaccine's tolerability and immune response.

Novartis claims that while 80 per cent of subjects who received one shot showed strong and potentially strong response, the number of persons with a similar response levels were 90 per cent when given two shots. MF-59 (to be sold under the brand name of Celtura) is an adjuvanted vaccine -which means it contains some other chemical to increase its efficacy.

“This is a positive development. But we still require bridging studies to generate Indian data before the vaccine is allowed to use,” Vishwa Mohan Katoch, director general of Indian Council of Medical Research told Deccan Herald.

Though live vaccines containing weakened forms of an infectious organism are sufficiently effective, vaccines containing dead organisms (inactivated vaccines) or pieces of the infectious organisms or their toxins (acellular or recombinant vaccines) need adjuvants to boost their efficiency levels.

The study for H1N1 vacccine did not include Non-adjuvanted formulations. It requires cold-chain for storage. The vaccine is currently undergoing a larger test with 6000 adults and children.