In the wake of the pandemic outbreak there is limited experience of how the next influenza season will evolve. Based on the current influenza situation in the Southern Hemisphere, it is likely that both the 2009 A (H1N1), A (H3N2) and B viruses will circulate in Norway during the upcoming influenza season, although it is impossible to predict which viruses will predominate. This autumn's seasonal influenza vaccine protects against the 2009 A (H1N1) virus in addition to an A (H3N2) virus and a B virus.
There have been no reports of mutations of clinical importance of the 2009 A (H1N1) virus. In the Southern Hemisphere, influenza caused by the 2009 A (H1N1) virus has so far had a clinical profile consistent with that seen during the pandemic. The same at-risk groups, including pregnant women, are among those who are most frequently affected by illness that requires hospitalisation.
Expanded recommendations for at-risk groups
The recommendations for the seasonal influenza vaccine have been expanded as it is expected that the 2009 A(H1N1) virus will cause influenza in Norway in the 2010/2011 season. This is to protect the risk groups who were particularly vulnerable during the 2009 pandemic and who have not previously been included in the Norwegian recommendations for the seasonal influenza vaccine. This includes:
- Pregnant women in their 2nd and 3rd trimester. Pregnant women in the 1st trimester with additional risk of complications may be considered for vaccination
- Adults and children with chronic liver failure
- Adults and children with chronic neurological disease or injury
- Adults and children who are morbidly obese, (body mass index (BMI) over 40 kg/m2 )
There is considerable experience with the use of the trivalent seasonal influenza vaccine, including for pregnant women, children and the elderly. Several countries, including the U.S.A., have given the vaccine to pregnant women for years.
The trivalent seasonal influenza vaccine is also recommended for pig farmers and other people who have regular contact with live pigs. This is to protect pig handlers from influenza infection and to prevent the development of virus mutations in swine herds.
The expanded recommendations are in addition to the usual at-risk groups, which include:
- People who are 65 years or older
- Adults and children with chronic lung diseases, especially those with impaired lung capacity
- Adults and children with chronic cardiovascular diseases, especially those with severe heart failure, low cardiac output or pulmonary hypertension
- Adults and children with weakened immune systems
- Adults and children with diabetes mellitus (both type 1 and type 2)
- Adults and children with chronic renal failure
- Residents in sheltered housing and nursing homes
Vaccination for health workers with regular patient contact is also recommended.