An approach to monitoring influenza vaccination uptake across Europe.

Currently, the monitoring of influenza vaccination uptake is mainly a national issue. As influenza infection easily crosses international borders, it is in the interest of all countries to have a high vaccine uptake in people who may be vulnerable when influenza spreads. A Europe-wide monitoring system can provide insight into the strengths and weaknesses of uptake rates in countries and, on ce sufficient levels are achieved, can safeguard the continuation of the achieved levels. This paper aims to address the following issues: a) How is influenza vaccination uptake monitored in Europe? b) What methods to monitor vaccination uptake are available and what are their limitations? c) What steps should be taken to implement a European-wide influenza vaccination uptake monitoring system? Based on existing literature and experiences in monitoring influenza vaccination uptake, an approach to set up a European-wide monitoring system is proposed. The following issues were identified as relevant for influenza vaccination uptake monitoring: a) Agreement on the population groups in which vaccination uptake should be monitored; b) The frequency of data collection; c) The importance of sharing experiences regarding existing influenza vaccination campaigns in order to learn from each other, and develop 'best practices'; d) The need to publish uptake data in close relation with influenza surveillance data and other European efforts on dissemination of vaccination knowledge. To stimulate the discussion on implementing a pan-European influenza uptake monitoring scheme the following recommendations were suggested : a) Develop a common set of variables; b) Build on experience from individual countries; c) Create a coordinating body; d) Create or identify a platform to publish the data; e) Start small and expand rapidly.

Epidemiological and virological assessment of influenza activity in Europe during the winter 2005-2006.

Influenza activity in Europe during the winter 2005-2006 started late January - early February 2006 and first occurred in the Netherlands, France, Greece and England. Subsequently, countries were affected in a random pattern across Europe and the period of influenza activity lasted till the end of April. In contrast to the winter seasons in the period 2001-2005, no west-east pattern was detected. In 12 out of 23 countries, the consultation rates for influenza-like illness or acute respiratory infection in the winter 2005-2006 were similar or higher than in the winter 2004-2005, despite a dominance of influenza B viruses that normally cause milder disease than influenza A viruses. In the remaining 11 countries the consultation rates were lower to much lower than in the winter 2004-2005. The highest consultation rates were usually observed among children aged 0-14. The circulating influenza virus types and subtypes were distributed heterogeneously across Europe. Although the figures for total virus detections in Europe indicated a predominance of influenza B virus (58% of all virus detections), in many countries influenza B virus was predominant only early in the winter, whilst later there was a marked increase in influenza A virus detections. Among the countries where influenza A viruses were co-dominant with B viruses (9/29) or were predominant (4/29), the dominant influenza A subtype was H3 in seven countries and H1 in four countries. The vast majority of characterised influenza B viruses (90%) were similar to the B/Victoria/2/87 lineage of influenza B viruses that re-emerged in Europe in the winter 2004-2005 but were not included in the vaccine for the influenza season 2005-2006. This might help to explain the dominance of influenza B viruses in many countries in Europe during the winter 2005-2006. The influenza A(H3) and A(H1) viruses were similar to the reference strains included in the 2005-2006 vaccine, A/California/7/2004 (H3N2) and A/New Caledonia/20/99 (H1N1), respectively. In conclusion, the 2005-2006 influenza epidemic in Europe was characterised by moderate clinical activity, a heterogeneous spread pattern across Europe, and a variable virus dominance by country, although an overall dominance of influenza B viruses that did not match the virus strain included in the vaccine was observed.

Epidemiological and virological assessment of influenza activity in Europe, during the 2004-2005 winter.

The 2004-2005 influenza season in Europe started in late December 2004 and the first influenza activity occurred in the west and southwest (Spain, United Kingdom and Ireland). Influenza activity then moved gradually east across Europe during January and early February 2005, and from late February until late March, most movement was south to north. The intensity of clinical influenza activity in ten out of 23 countries was higher than during the 2003-2004 season, and lower or equal to the 2003-2004 season in the other 13 countries. The highest consultation rates were generally observed among children aged 0-14 years. However, the peak consultation rates due to influenza-like illness or acute respiratory infection were not especially high when compared with historical data. The predominant virus strain was influenza A (83% of total detections) of the H3 subtype (85% of H-subtyped A viruses), with fewer influenza B (17% of total detections) or A(H1) viruses (15 % of H-subtyped A viruses) detected. The vast majority of A(H3) viruses were similar to the reference strains A/Wellington/1/2004 (H3N2) and, subsequently, A/California/7/2004 (H3N2) that are closely related drift variants of the A/Fujian/411/2002 (H3N2) prototype vaccine strain. The B viruses co-circulated with A viruses during the whole influenza season in 11 out of 24 countries. Seven of these were located in the northeast of Europe and in these countries the proportion of B viruses was higher (range: 31-60%) than in the rest of Europe (range: 6-26%). In 13 out of 24 countries the B viruses circulated relatively late in the season. About 43% of all antigenically characterised B viruses were B/Hong Kong/330/2001-like (B/Victoria/2/87 lineage), a strain that is distinguishable from the vaccine influenza B strain, which was a B/Yamagata/16/88 lineage virus. Based on the viruses detected worldwide until February 2005, the World Health Organization modified the composition of the 2005-2006 influenza vaccine from the 2004-2005 season vaccine to include a new A(H3N2) component: an A/California/7/2004 (H3N2)-like virus.

Epidemiological and virological assessment of influenza activity in Europe, during the 2004-2005 winter.

The 2004-2005 influenza season in Europe started in late December 2004 and the first influenza activity occurred in the west and southwest (Spain, United Kingdom and Ireland). Influenza activity then moved gradually east across Europe during January and early February 2005, and from late February until late March, most movement was south to north. The intensity of clinical influenza activity in ten out of 23 countries was higher than during the 2003-2004 season, and lower or equal to the 2003-2004 season in the other 13 countries. The highest consultation rates were generally observed among children aged 0-14 years. However, the peak consultation rates due to influenza-like illness or acute respiratory infection were not especially high when compared with historical data. The predominant virus strain was influenza A (83% of total detections) of the H3 subtype (85% of H-subtyped A viruses), with fewer influenza B (17% of total detections) or A(H1) viruses (15 % of H-subtyped A viruses) detected. The vast majority of A(H3) viruses were similar to the reference strains A/Wellington/1/2004 (H3N2) and, subsequently, A/California/7/2004 (H3N2) that are closely related drift variants of the A/Fujian/411/2002 (H3N2) prototype vaccine strain. The B viruses co-circulated with A viruses during the whole influenza season in 11 out of 24 countries. Seven of these were located in the northeast of Europe and in these countries the proportion of B viruses was higher (range: 31-60%) than in the rest of Europe (range: 6-26%). In 13 out of 24 countries the B viruses circulated relatively late in the season. About 43% of all antigenically characterised B viruses were B/Hong Kong/330/2001-like (B/Victoria/2/87 lineage), a strain that is distinguishable from the vaccine influenza B strain, which was a B/Yamagata/16/88 lineage virus. Based on the viruses detected worldwide until February 2005, the World Health Organization modified the composition of the 2005-2006 influenza vaccine from the 2004-2005 season vaccine to include a new A(H3N2) component: an A/California/7/2004 (H3N2)-like virus.