TORONTO -- New data from U.S. studies seems to confirm that only one dose of H1N1 vaccine will be needed to protect adults and seniors and that giving seasonal and pandemic flu shots at the same time should be fine, the head of the National Institute of Allergy and Infectious Diseases said Friday.
Testing showed that adults and seniors who received a second dose of the pandemic vaccine didn't get much additional benefit from the second shot, Dr. Anthony Fauci said in a media teleconference.
The response to one dose in both groups was already sufficiently strong to suggest that the vaccine should offer good protection and it has been the working assumption in the U.S. that adolescents and adults would only need one shot.
"We have data that looked good and suggesting to us (that) one dose of 15 micrograms would be sufficient for the adults and elderly," said Fauci, who added there was "no substantial difference between the second dose and (antibody levels seen at) 21 days following the first dose."
"That confirms the concept that a single dose of 15 micrograms is sufficient enough to induce a robust response."
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Fauci also revealed preliminary data from another study looking at whether it was safe to give both seasonal and pandemic flu shots at the same. Both protect against an H1N1 virus -- though the viruses are sufficiently different it is thought vaccine against one would not protect against the other.
There were theoretical concerns, though, that giving two flu vaccines at once might interfere with the immune system's ability to generate a good response to all the viruses covered in the shots. Seasonal flu shots protect against three families of viruses -- seasonal H1N1 and H3N2, both influenza A viruses and an influenza B virus.
"The vaccine when given simultaneously does not impair the immune response to either of those (shots)," Fauci said.
"That I believe is going to be important as we roll out the vaccination program. And individuals will go to their offices and would like at the same time to get both vaccinations."
Fauci said there were no unusual side-effects seen in the people who received the two vaccines together. "We're seeing pain, redness and perhaps some swelling that we see very frequently with injectable vaccines."
He said his institute is now launching new trials, studying the safety and effectiveness of the vaccine in people with asthma. Other studies will look at safety and dosing requirements in two groups of people living with HIV -- pregnant women, and children and adolescents.
