An analysis of national target groups for monovalent 2009 pandemic influenza vaccine and trivalent seasonal influenza vaccines in 2009-10 and 2010-11

Abstract

Background: Vaccination is generally considered to be the best primary prevention measure against influenza virus infection. Many countries encourage specific target groups of people to undertake vaccination, often with financial subsidies or a priority list. To understand differential patterns of national target groups for influenza vaccination before, during and after the 2009 influenza pandemic, we reviewed and analyzed the country-specific policies in the corresponding time periods.

Methods: Information on prioritized groups targeted to receive seasonal and pandemic influenza vaccines was derived from a multi-step internet search of official health department websites, press releases, media sources and academic journal articles. We assessed the frequency and consistency of targeting 20 different groups within populations which are associated with age, underlying medical conditions, role or occupations among different countries and vaccines. Information on subsidies provided to specific target groups was also extracted.

Results: We analyzed target groups for 33 (seasonal 2009 and 2009-10 vaccines), 72 (monovalent pandemic 2009-10 vaccine) and 34 (seasonal 2010 and 2010-11 vaccines) countries. In 2009-10, the elderly, those with chronic illness and health care workers were common targets for the seasonal vaccine. Comparatively, the elderly, care home residents and workers, animal contacts and close contacts were less frequently targeted to receive the pandemic vaccine. Pregnant women, obese persons, essential community workers and health care workers, however, were more commonly targeted. After the pandemic, pregnant women, obese persons, health care and care home workers, and close contacts were more commonly targeted to receive the seasonal vaccine compared to 2009-10, showing continued influence from the pandemic. Many of the countries provided free vaccines, partial subsidies, reimbursements or national health insurance coverage to specific target groups and over one-third of the countries offered universal subsidy regarding the pandemic vaccine. There was also some inconsistency between countries in target groups.

Conclusions: Differences in target groups between countries may reflect variable objectives as well as uncertainties regarding the transmission dynamics, severity and age-specific immunity against influenza viruses before and after vaccination. Clarification on these points is essential to elucidate optimal and object-oriented vaccination strategies.

Figure 1

Groups prioritized to receive the 2009 and 2009-10 seasonal trivalent influenza vaccine (black square), 2009 monovalent pandemic influenza vaccine (black open circle), and 2010 and 2010-11 seasonal trivalent influenza vaccine (gray square) in countries located in Asia and the Pacific, and the Americas. Groups subsidized to receive the vaccine for free (f), at a cost with partial subsidy (p), with reimbursable cost (r) or insured by national health insurance (i) were also denoted. Target group abbreviations: 0-5 (0-5 years), 6-11 (6-11 years), 12-15 (12-15 years), 16-39 (16-39 years), 40-64 (40-64 years), 65+ (65 years or over), prg (pregnant), chr (chronic illness, obe (obesity), dis (disabled), hcw (health care workers), lab (laboratory workers), con (close contacts), res (care home residents), chw (care home workers), tch (teachers), ani (animal contacts), ecw (essential community workers), abo (aboriginals), trv (travelers).

Figure 2

Groups prioritized to receive the 2009 and 2009-10 seasonal trivalent influenza vaccine (black square), 2009 monovalent pandemic influenza vaccine (black open circle), and 2010 and 2010-11 seasonal trivalent influenza vaccine (gray square) in countries located in Europe and Africa. Groups subsidized to receive the vaccine for free (f), at a cost with partial subsidy (p), with reimbursable cost (r) or insured by national health insurance (i) were also denoted. Abbreviations for age, underlying medical conditions, role and occupation are the same as those employed in Figure 1.

Figure 3

The frequency of risk groups prioritized to receive the seasonal trivalent influenza vaccine, 2009 monovalent pandemic influenza vaccine, and 2010 and 2010-11 trivalent seasonal influenza vaccine in 31 countries in which the target group information were found for all 3 vaccines. Abbreviations for age, underlying medical conditions, role and occupation are the same as those employed in Figure 1. White grid lines are included at 10% intervals.

Figure 4

The pairwise consistency of target groups between the 2009 and 2009-10 trivalent seasonal influenza vaccine, the 2009-10 monovalent pandemic influenza vaccine and the 2010 and 2010-11 trivalent seasonal influenza vaccines. Points show the estimates of the multiple-rater agreement AC₁ statistics, lines show the bootstrap-based 95% confidence intervals. Abbreviations for age, underlying medical conditions, role and occupation are the same as those employed in Figure 1.

Figure 5

The consistency of target groups between the 31 countries in which the target group information were found for all 3 vaccines. Points show the estimates of the multiple-rater agreement AC₁ statistics, lines show the bootstrap-based 95% confidence intervals. Abbreviations for age, underlying medical conditions, role and occupation are the same as those employed in Figure 1.