Americans testing higher dose of swine flu vaccine in HIV-positive women and young people

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Clinical trials are underway in the US to test the safety and effectiveness of the swine flu (H1N1) vaccine in HIV-positive women and younger people.

Individuals recruited to these studies will receive two 30 microgram doses of the vaccine. This is twice the dose investigated in HIV-negative pregnant women and younger people. The higher dose is being tested because research into the development of seasonal flu vaccines showed that individuals with HIV had stronger, longer-lasting immune responses if they were given a larger dose of the vaccine than HIV-negative individuals.

The study is being conducted in pregnant women and younger people (aged four to 24 years) because swine flu is disproportionately affecting these groups. It is not yet known if HIV-positive pregnant women and younger people have an increased risk of complications arising from swine flu.

Glossary

immune response

The immune response is how your body recognises and defends itself against bacteria, viruses and substances that appear foreign and harmful, and even dysfunctional cells.

“These studies are important because HIV infection and pregnancy both increase the risk for a poor immune response to the normal 15-microgram dose of seasonal flu vaccine given in the general population,” said Dr Anthony Fauci of the US National Institute of Allergy and Infectious Diseases.

The vaccine will be investigated in 130 HIV-positive pregnant women aged 18 to 39 in the third trimester of pregnancy. The second study will involve 140 children and young adults.

Two doses of the vaccine will be provided, the first at baseline and the second three weeks later.

“These trials are testing whether doses of the licensed 2009 H1N1 influenza vaccine that are higher than doses being tested in other groups can safely elicit protective immune responses in HIV-infected children, youth and pregnant women,” said Dr Lynne Mofenson of the US National Institute of Child Health and Human Development.

Pregnant women will be tested for antibody responses to the vaccine after each dose. Samples of tissue from the umbilical cord will also be tested for antibodies to swine flu to see if they are being transferred from mothers to infants. The infants will also be monitored three and six months after birth to see if maternal vaccination provided them with protection against swine flu.

Antibody responses in young people will be assessed 21 days after the first dose, ten days after the second, and again six months after entering the study.

As with all clinical trials, information on the safety of the vaccine will be gathered and closely monitored by an independent committee.