Recommendations that patients with HIV should be vaccinated against influenza “are justified,” according to an editorial in the January 1st edition of Clinical Infectious Diseases, and the use of the vaccine “should be encouraged.”
The author, Dr Raphael Dolin of the Harvard Medical School, reviewed three studies published in the same edition of the journal that examined the safety and efficacy of influenza vaccination in patients with HIV.
Numerous studies have previously examined the impact of influenza vaccination on patients with HIV. However, these produced inconsistent results and many were conducted before the introduction of effective antiretroviral therapy.
There were therefore unanswered questions about the efficacy of vaccinations.
So in 2009 investigators in South Africa undertook a study to compare the effectiveness of the vaccine against influenza A H1N1 (swine flu) in HIV-positive and HIV-negative patients. All were aged between 18 and 50 and received a single dose of the vaccine via injection.
The HIV-positive patients had a median CD4 cell count of 581 cells/mm3 and 82% were taking antiretrovirals. Despite having well-preserved immune function individuals with HIV were significantly less likely than HIV-negative patients to develop protective antibodies against influenza after receiving the vaccine (56% vs. 80%, p = 0.003).
Some investigators have suggested that the provision of additional doses would improve responses to influenza vaccination among patients with HIV. This question was examined in a German study.
A total of 135 patients were recruited and received two doses of the H1N1 vaccine. Antibody responses were monitored 21 days after the administration of each dose. After the first injection, 68% developed protective antibodies. This increased to 92% after the administration of the second injection. A higher CD4 cell count was associated with antibody responses to the vaccinations.
There are also questions about the impact of influenza immunisation on CD4 cell count and viral load and the clinical effectiveness of vaccination. These issues were addressed in a third study published in the journal.
The research was conducted in South Africa and involved 506 HIV-positive adults, 349 of whom were taking antiretroviral therapy. The patients were randomised to receive the trivalent, inactivated influenza vaccine. The World Health Organization recommended this vaccine for use in the Southern Hemisphere in 2008.
Dr Dolin praised the study as “well-designed and conducted.” However, he noted that patients with more advanced HIV infection were excluded from participation in this study, as were those with co-morbidities that are associated with influenza complications.
Vaccination did not reduce CD4 cell count or increase viral load among the patients taking HIV therapy.
In addition, receipt of the vaccine reduced the risk of laboratory confirmed influenza by 76%.
Recommendations that patients with HIV should be vaccinated against influenza are therefore justified and individuals should be encouraged to receive them, concluded Dr Dolin.
He added that efforts are still required to improve immune responses to vaccination, and studies should be undertaken on the effects of “additional doses, modified vaccination regimens, and novel adjuvants and novel influenza vaccines in this patient population.”
Dolin R. Perspectives on the role of the immunization against influenza in HIV- infected patients. Clin Infect Dis 52: 147-49, 2011 (click here for access to the free full text).
Crum-Cianflone NI et al. Immunogenicity of a monovalent 2009 influenza A (H1N1) vaccine in an immunocompromised population: a prospective study comparing HIV-infected adults with HIV-uninfected adults. Clin Infect Dis 52: 138-46, 2011 (click here for access to the free full text).
Bickel M et al. Immune response after two doses of the novel split virion, adjuvanted pandemic H1N1 Influenza A vaccine in HIV-1–infected patients. Clin Infect Dis 52: 122-27, 2011 (click here for access to the free full text).
Madhi SA et al. Trivalent inactivated influenza vaccine in African adults infected with Human Immunodeficient Virus: double blind, randomized clinical trial of efficacy, immunogenicity, and safety. Clin Infect Dis 52: 128-37, 2011 (click here for access to the free full text).