Swine Flu & Immunosuppression

Swine flu and immunosuppression

http://www.nhs.uk/news/2009/07July/Pages/Swinefluandimmunosuppression.aspx

A review of research on how flu affects immunosuppressed people and the effects of vaccination on them has been published in The Lancet Infectious Diseases. The authors specifically looked at susceptibility in people with HIV/AIDS, cancer, those who have had a solid organ transplant or bone-marrow transplant and patients on haemodialysis or steroids.

Such groups are thought to be at higher risk of serious influenza-associated complications and as such are priority groups for immunisation.

However, treatments for immune dysfunction may also limit the effectiveness of vaccination and there may be complications from the vaccination itself in these groups. The evidence behind these issues is discussed in this review.

 

Key points from the review

• There is little research on using vaccination to prevent influenza in immunosuppressed people. This review found just one randomised clinical trial. This trial of HIV-infected patients found high vaccine effectiveness.
• The same immune dysfunction that can increase the risk and consequences of influenza infection might also compromise vaccine responses and effectiveness.
• Most immunosuppressed populations are at higher risk of influenza-associated complications, have a general trend toward impaired antibody responses but can be safely vaccinated.
• The priority for control of influenza is focused on generating effective antibody responses with vaccines. Progress is being made at increasing the scale, duration, and breadth of vaccine responses to the two main surface proteins H and N (haemagglutinin and neuraminidase) in both healthy and immuno-compromised populations.
• There are two main types of influenza vaccine and both are being developed for the new H1N1 swine flu virus. One involves inactivated vaccines that contain viruses grown in eggs (mostly) and then killed. The other involves live weakened H1N1 vaccines.  The researchers say that previous concerns that these live attenuated vaccine would pose a risk to people that are immunocompromised have not been demonstrated by the studies in their review. Research into this area and into and other novel approaches to flu vaccine development are important. They ask that efficacy studies of attenuated vaccines in adults that are immunocompromised are also considered

Systemic corticosteroids

The authors also looked at people taking oral or inhaled steroids, saying that the evidence shows flu vaccination is both safe and often stimulates an immune response. However, the vaccine’s clinical effectiveness in reducing episodes of flu in people taking the drugs has not been well tested.

 

What were the researchers’ conclusions?

The researchers say that most immunosuppressed populations are at higher risk of influenza-associated complications. These people have impaired antibody responses to the vaccine (although data for this conclusion is mixed. For example, in some trials, HIV patients with low CD4+ counts developed only 30% of the antibody response of healthy controls, and in one trial of patients on chemotherapy, there was even less of a response. However, other studies have shown that patients who have had haemodialysis and transplant managed up to 80% protective titres.

They say that most immunosuppressed people can be safely vaccinated (although longitudinal data that follows up patients over time are largely lacking).

They also say that the small number of studies of cellular responses to influenza vaccination, in relatively small numbers of immunosuppressed individuals, showed impaired cellular responses among a few patients.

The researchers call for better trial data to inform vaccination recommendations based on the effectiveness and cost in these at-risk populations.