Commission staff working document - Vaccination strategies against pandemic (H1N1) 2009 accompanying the Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions - Pandemic (H1N1) 2009 {COM(2009) 481} {SEC(2009) 1188} {SEC(2009) 1190} {SEC(2009) 1191} {SEC(2009) 1192}
Date: 2009-09-15
Institutions: European Commission
Subjects: disease prevention, epidemiology, health control, health risk, infectious disease, public health, vaccination, vaccine

EN 

EN 

   EN 

 
 
COMMISSION OF THE EUROPEAN COMMUNITIES 

Brussels, 15.9.2009 
SEC(2009) 1189 final 

COMMISSION STAFF WORKING DOCUMENT 

Vaccination strategies against pandemic (H1N1) 2009  

accompanying the 

COMMUNICATION FROM THE COMMISSION TO THE EUROPEAN 
PARLIAMENT, THE COUNCIL, THE EUROPEAN ECONOMIC AND SOCIAL 
COMMITTEE AND THE COMMITTEE OF THE REGIONS 

Pandemic (H1N1) 2009 

{COM(2009) 481} 
{SEC(2009) 1188} 
{SEC(2009) 1190} 
{SEC(2009) 1191} 
{SEC(2009) 1192} 

EN 

   EN 

 
 
 
  
 
 
 
INTRODUCTION 

In  April  2009,  a  novel  strain  of  a  human  influenza  A(H1N1)  virus  was  identified  that  had 
caused illness in Mexico and the United States first, in March and April 2009. 

On 11 June 2009, the World Health Organisation (WHO) declared a pandemic, caused by the 
novel  influenza  A(H1N1)  virus,  hereafter  called  'pandemic  (H1N1)  2009  influenza  virus'. 
This declaration was in line with WHO’s global influenza preparedness plan where phase 6, 
the pandemic phase, is defined as the virus causing sustained community-level outbreaks in at 
least two countries in one WHO region and in at least one other country in a different WHO 
region.  The  declaration  therefore  reflected  the  spread  of  the  new  virus,  not  the  severity  of 
illness caused by it. 

Current experience is that some ‘higher risk’ groups are more likely to suffer severe illness if 
infected (people with underlying chronic conditions1, pregnant  women and  young children). 
Most  patients  have  suffered  only  a  mild,  self-limiting  illness  and  the  health  services  have 
generally coped. 

Notwithstanding  the  moderate  symptoms  caused  by  the  pandemic  (H1N1)  2009  influenza 
virus  so  far,  the  wide  spread  of  the  virus  poses  a  potentially  serious  threat.  In  the  winter 
ahead, the virus could transmit more easily and there will be more other respiratory infections 
than in summer. In addition, it cannot be ruled out that the pandemic (H1N1) 2009 influenza 
virus  might  mutate  or  exchange  genetic  material  with  other  influenza  viruses,  which  could 
lead to it causing a more severe illness. 

Vaccines  play  an  important  role  in  the  preparations  for  the  increase  in  infections  by  the 
pandemic  (H1N1)  2009  influenza  virus  expected  from  the  autumn  onwards.  Indeed, 
vaccination with a pandemic vaccine effective against the pandemic (H1N1) 2009 influenza 
virus  can  be  considered  as  one  of  the  most  effective  public  health  measures  in  that  it  both 
offers  protection  to  the  individual  and  prevents  onward  transmission.  Obviously,  the  public 
health  response  should  not  rely  on  vaccination  alone  but  should  also  include  other  public 
health  measures,  both  pharmaceutical  (e.g.  antivirals)  and  non-pharmaceutical  (e.g.  social 
distancing or personal protective equipment).  

As  specific  vaccines  cannot  be  developed  until  the  pandemic  influenza  strain  has  been 
isolated,  the  vaccine  will  initially  be  available  in  only  limited  quantities  and  demand  may 
initially  be  higher  than  supply.  In  addition,  the  yield  of  pandemic  (H1N1)  2009  influenza 
antigen to produce vaccines might be lower than the yield usually seen for seasonal influenza 
strains, which, in turn, would limit supply. The initial limited availability of vaccines, together 
with the potential need for a large-scale vaccination campaign, poses challenges to healthcare 
systems and highlights the need for a carefully planned vaccination strategy. 

This Commission Staff Working Document outlines a possible vaccination strategy based on 
the  evidence  currently  available,  while  recognising  that  the  responsibility  for  developing  a 
vaccination strategy against pandemic (H1N1) 2009 lies with the Member States. Therefore, 

1 

E.g. chronic respiratory diseases; chronic cardiovascular diseases, excluding isolated mild hypertension; 
chronic  metabolic  disorders,  notably  diabetes;  chronic  renal  and  hepatic  diseases;  persons  with 
congenital or acquired immunodeficiency; chronic neurological or neuromuscular conditions. 

EN 

2 

   EN 

 
                                                 
Member  States  may  develop  different  vaccination  strategies,  taking  into  account  their 
epidemiology, health service structures and available resources. It should also be stressed that 
any  vaccination  strategy  might  need  to  be  adapted  as  more  epidemiological,  clinical  and 
pharmaceutical  evidence  becomes  available  and  as  the  pandemic  progresses.  Vaccination 
strategies against pandemic (H1N1) 2009 will therefore need to be reviewed regularly. 

1. 

POSSIBLE OBJECTIVES OF VACCINATION 

On  7  July  2009,  the  WHO  Strategic  Advisory  Group  of  Experts  (SAGE)  on  Immunisation 
identified  three  objectives  that  countries  could  adopt  as  part  of  their  pandemic  vaccination 
strategy: 

•  protect  the  integrity  of  the  healthcare  system  and  the  country’s  critical  infrastructure, 

i.e. maintain essential services; 

•  reduce morbidity and mortality, i.e. protect the vulnerable; 

•  reduce  transmission  of  the  pandemic  virus  within  communities,  i.e.  limit  the  speed  of 

spread of infection and limit the burden on the healthcare system. 

The categories of people who would be covered by those three objectives are listed in Table1. 

Table  1.  Rough  estimates2  of  the  numbers  of  EU  citizens  who  would  be  covered  by  the  three 
objectives identified by SAGE 

Population 

% of the whole 
population 

Objective: maintain essential services (approximately 6 %) 

Healthcare workers 

Workers in other essential services 

Subtotal 

Objective: protect the vulnerable (approximately 29 %) 

Very young children (0-24 months) 

Persons aged between 25 months and 64 years 
with underlying chronic conditions increasing the 
risk of severe disease 

Pregnant women  

People aged 65 and older 

Subtotal 

10,000,000 

20,000,000

30,000,000

10,000,000

40,000,000

7,500,000

85,000,000

142,500,000

2 %

4 %

6 %

2 %

8 %

1.5 %

17 %

28.5 %

2 

Note: percentages have been rounded, so the subtotals do not add up exactly. 

EN 

3 

   EN 

 
 
                                                 
Objective: limit the speed of spread of infection and the burden on the healthcare system 
(approximately 65 %) 

Healthy  children  and  adolescents  aged  between 
25 months and 18 years 

85,000,000

Healthy adults not included in the previous groups 

240,000,000

Subtotal 

Total population (EU27) 

325,000,000

500,000,000

1.1.  Maintaining essential services 

17 %

48 %

65 %

100.0 %

During  a  pandemic,  there  is  likely  to  be  a  degree  of  absenteeism  from  work.  In  the  United 
Kingdom, it has been estimated that 12 % of the adult population will be off work at the peak 
of  the  pandemic3.  A  survey  led  by  researchers  at  the  Johns  Hopkins  Bloomberg  School  of 
Public Health found that approximately one in six public health workers (approximately 16 %) 
said they would not report to work during an influenza pandemic, regardless of its severity4. 

Organisations  will  need  to  assess,  in  their  business  continuity  plans,  whether  such  levels  of 
absenteeism would be disruptive to their activities. This applies, in particular, to organisations 
which deliver services essential to keep society working. Examples include but are not limited 
to: 

•  Healthcare workers; 

•  People  working  in  command  and  control  centres  and  in  essential  services  such  as  (in  no 

specific order): 

•  electronic communications; 

•  security (law and order); 

•  civil protection services and other first responders; 

•  electricity production and distribution; 

•  water supply; 

•  food production and distribution (including transport); 

•  oil and gas recovery, processing and distribution (including transport); 

•  public transport systems; 

3

4 

EN 

http://www.dh.gov.uk/en/Publicationsandstatistics/Publications/PublicationsPolicyAndGuidan

ce/DH_102892. 
Barnett, D.J., Balicer, R.D., Thompson, C.B., Storey, J.D., Omer, S.B. et al., 2009 Assessment of Local 
Public  Health  Workers’  Willingness  to  Respond  to  Pandemic  Influenza  through  Application  of  the 
Extended Parallel Process Model. PLoS ONE 4(7): e6365. doi:10.1371/journal.pone.0006365. 

4 

   EN 

 
                                                 
 
•  financial and logistics services. 

Essential services might need to be targeted for vaccination against pandemic (H1N1) 2009 
influenza, especially those where the estimated levels of absenteeism would disrupt operation 
of the service. This applies, in particular, to healthcare workers who, in addition, will have to 
cope with far higher numbers of patients than usual. 

1.2. 

Protecting the vulnerable 

According  to  the  current  evidence  on  pandemic  (H1N1)  2009,  the  following  population 
groups are considered at higher risk of severe pandemic (H1N1) 2009 influenza infection than 
the general population: 

•  people  with  underlying  chronic  conditions  increasing  the  risk  for  severe  disease  (e.g. 
chronic  respiratory  diseases;  chronic  cardiovascular  diseases,  excluding  isolated  mild 
hypertension;  chronic  metabolic  disorders,  notably  diabetes;  chronic  renal  and  hepatic 
diseases;  persons  with  congenital  or  acquired  immunodeficiency;  chronic  neurological  or 
neuromuscular conditions.), 

•  young children (especially those aged 0 – 24 months), 

•  pregnant women. 

Details of the evidence of the risk of people developing severe disease when infected with the 
pandemic  (H1N1)  2009  influenza  virus  are  available  in  the  European  Centre  for  Disease 
Prevention  and  Control  (ECDC)  risk  assessment,  which  is  updated  regularly5.  As  further 
epidemiological  data  become  available,  the  population  groups  considered  vulnerable  and  at 
risk of severe infections could change. 

The  above-mentioned  groups  differ  somewhat  from  the  groups  for  whom  many  countries 
recommend  seasonal  influenza  immunisation.  Notably,  elderly  people  are  missing.  It  is 
speculated  that  elderly  people  are  affected  less  because  they  possibly  have  some  residual 
immunity  from  previous  exposure  to  viruses  in  some  ways  similar  to  the  pandemic  (H1N1) 
2009 influenza virus. However, it seems that not all elderly people are immune and those who 
do become infected suffer a more severe disease. Therefore some elderly people are at higher 
risk  of  developing  severe  disease,  but  they  cannot  be  readily  identified.  Given  this 
uncertainty, there is merit in including this age group as a target for vaccination. 

1.3. 

Limiting the spread of infection: projection on immunisation coverage needed 

To  reduce  or  eliminate  influenza  from  the  host  population,  a  reduction  in  transmission  is 
necessary.  This  can  be  achieved  by  means  such  as  vaccination.  Vaccination 
is, 
epidemiologically speaking, an attempt to reduce the reproductive number R0 (the number of 
secondary cases produced by each infectious case) to below 1. 

The  decisive  question  is  what  fraction  of  the  population  needs  to  be  vaccinated  in  order  to 
produce enough immune people to make sure that the infectious persons will not be able to 
infect  one  other  person  on  average.  If  the  fraction  of  the  population  susceptible  is  small 

5 

http://www.ecdc.europa.eu/en/Health%5Ftopics/novel%5Finfluenza%5Fvirus/2009%5FOutbreak/. 

EN 

5 

   EN 

 
                                                 
enough,  the  probability  that  an  infective  host  will  come  into  contact  with  a  susceptible 
individual before recovering will be very low. 

For the current influenza pandemic, the estimates point to an R0 value of about 1.6. Assuming 
a hypothetical vaccine efficacy of 70 % (as often seen with seasonal influenza vaccines), the 
fraction of the population which would have to be vaccinated would be at least 54 %6. 

This  (over-)simplified  calculation  assumes  that  everybody  would  be  equally  affected  by  the 
disease, that there would be random mixing of the population, that the vaccine would have the 
same  efficacy  in  everybody  and  that  protective  (susceptible)  efficacy  is  equal  to 
infectiousness efficacy. Nevertheless, it gives a rough indication to support policy decisions 
on immunisation coverage. 

Epidemiological  data  on  pandemic  (H1N1)  2009  influenza  suggest  that  immunisation  of 
children and young adults could be particularly effective in reducing transmission. 

2. 

POTENTIAL TARGET GROUPS AND PRIORITY GROUPS FOR VACCINATION 

Target groups are all the people for whom vaccination can be recommended. 

Priority groups are the people within the target groups who should be vaccinated first if not 
enough vaccine is initially available for everyone in the target groups. Even if enough vaccine 
were  available,  distributing  large  quantities  of  vaccine  and  vaccinating  large  numbers  of 
people takes time. 

Balancing the three objectives described previously, the following can be considered potential 
target groups for vaccination, covering between 34 % and 60.5 % of the total population: 

•  Maintaining essential services: 

•  healthcare workers (2 %); 

•  workers in other essential services (4 %). 

•  Protecting the vulnerable: 

•  all persons aged from 6 months to 24 months (1.5 %)7; 

•  all persons aged from 25 months to 64 years with underlying chronic conditions 

increasing the risk of severe disease (8 %); 

•  pregnant women (1.5 %); 

6 

7 

If  a  vaccine  confers  complete  immunity  on  everyone  who  is  immunised,  a  fraction  f  >  1  —  (1/R0) 
would need to be vaccinated. If the vaccine confers immunity on only a fraction V1 of the population 
(not all vaccinated people will have a sufficient immune response to the vaccine to build up protective 
immunity), then f = V times V1 and thus V > (1 — (1/R0)) / V1. 
The 0–6  months  age group has not  been  included,  given  the  absence of  a vaccine  for  this  age group. 
This  vulnerable  age  group  can  be  protected  by  other  pharmaceutical  and  non-pharmaceutical  public 
health measures. Immunising pregnant women will probably also afford some protection to newborns 
via maternal antibodies. 

EN 

6 

   EN 

 
                                                 
•  all persons aged 65 years and more (17 %)8. 

•  Limiting the spread of infection, depending on the epidemiology, health service structures 

and available resources: 

•  all persons aged from 25 months up to young adults, e.g. up to 18 years to cover 
children and young adults up to the end of secondary education (17 %) or 24 years 
to cover children and young adults up to the end of tertiary education (26.5 %). 

It should be stressed that the eventual target groups will depend on the national targets set by 
the Member States. In some cases, this may be the entire population and in other cases only 
specific groups. 

However, it is unlikely that the vaccine will be immediately available for all target groups at 
the  same  time  and  therefore,  it  is  necessary  to  define  priority  groups.  The  European  Union 
Health  Security  Committee  and  the  Early  Warning  and  Response  authorities  (HSC/EWRS) 
adopted  on  25  August  2009  a  policy  statement9  proposed  by  the  European  Commission  in 
which  the  following  19.5 %  of  the  population  was  identified  for  prioritisation  when  limited 
amounts of vaccine are available: 

•  healthcare workers (2 %); 

•  all  persons  aged  from  six  months  on  with  underlying  chronic  conditions 

increasing the risk of severe disease (16 %); 

•  pregnant women (1.5 %). 

This prioritisation is designed to include the essential services which face the highest risk of 
being overloaded during a pandemic and also the vulnerable groups at greatest risk of severe 
illness following infection with the pandemic (H1N1) 2009 influenza virus. 

It  should  be  stressed  that  the  responsibility  for  developing  a  vaccination  strategy  against 
pandemic (H1N1) 2009 lies with the Member States. Therefore, Member States may develop 
different  vaccination  strategies,  taking  into  account  their  epidemiology,  health  service 
structures, available resources and cost-effectiveness of available vaccines. 

The decisions on target groups and priority groups could also be influenced by the choice of 
pandemic  (H1N1)  2009  influenza  vaccine  (e.g.  adjuvanted  versus  unadjuvanted  vaccine  or 
inactivated whole virion vaccine versus surface antigen/split virus vaccine) and by marketing 
authorisation conditions for the available vaccines. and by the benefit/risk profile of available 
vaccines for individual population groups. 

It  should  also  be  added  that  some  of  the  above-mentioned  groups  might  change  as  more 
epidemiological, clinical and pharmaceutical evidence becomes available and as the pandemic 
progresses.  Potential  target  groups  and  priority  groups  for  vaccination  against  pandemic 
(H1N1) 2009 influenza will therefore need to be reviewed regularly. 

8 

9 

Given the uncertainty on whom has residual immunity from previous exposure to viruses in some ways 
similar  to  the  pandemic  (H1N1)  2009  influenza  virus,  there  is  merit  in  including  this  age  group  as  a 
target for vaccination (see Section 1.2). 
http://ec.europa.eu/health/ph_threats/com/Influenza/docs/HSC_EWRS_statement_en.pdf 

EN 

7 

   EN 

 
                                                 
3. 

TIMING OF VACCINATION CAMPAIGNS 

Vaccination  of  priority  groups  should  start  as  soon  as  pandemic  (H1N1)  2009  influenza 
vaccines  become  available.  This  should  be  followed  by  vaccination  of  target  groups.  It  is 
recommendable  to  continue  to  vaccinate  unimmunised  individuals  and  not  keep  vaccine  in 
reserve for later administration of the second dose. The second dose can be given three to four 
weeks later, as additional supplies become available. 

4. 

VACCINATION CAPACITY OF HEALTHCARE SYSTEMS 

4.1. 

Vaccine supply 

First  of  all,  vaccine  supply  will  determine  the  vaccination  capacity  of  healthcare  systems. 
Prudent estimates put the annual global production capacity for pandemic influenza vaccine at 
2.45 billion monovalent doses. European influenza vaccine manufacturers account for 60 % of 
the  global  production  capacity,  i.e.  approximately  1.5  billion  monovalent  doses,  of  which  a 
large  proportion  could  be  exported  outside  Europe,  as  is  the  case  for  seasonal  influenza 
vaccines. Also, the full annual production will only gradually become available. As a result, 
especially  in  the  initial  phase,  demand  could  be  higher  than  supply.  Anticipating  limited 
supplies,  an  increasing  number  of  Member  States  have  concluded  advance  purchase 
agreements with one or more influenza vaccine manufacturers to reserve a set proportion of 
the available production capacity for pandemic influenza vaccine. 

4.2. 

Logistics 

Appropriate  arrangements  will  need  to  be  made  for  distributing  and  storing  sufficient 
quantities of vaccines and medical material (syringes, needles, alcohol swabs, etc.), including 
sufficient capacity to maintain the cold chain of vaccines. Administration of vaccines to target 
populations as soon as vaccine arrives should be the aim. 

4.3. 

Vaccination capacity 

To  avoid  overburdening  healthcare  facilities  in  the  event  of  a  mass  vaccination  campaign, 
Member  States  could  consider  spreading  the  settings  in  which  vaccination  will  take  place 
between healthcare facilities, schools, work places, function venues, etc., in accordance with 
any provisions in national and regional pandemic preparedness plans. In such cases, Member 
States  would  need  to  consider  whether  the  chosen  settings  will  be  capable  of  providing 
vaccine, registering vaccination, recalling patients for their second dose within three or four 
weeks, depending on which vaccine is used, and monitoring and reporting adverse events.  

Depending on the results of the scientific studies on the vaccine, either one or two doses of 
vaccine  are  expected  to  be  needed  to  achieve  protective  immunity.  Currently  we  are 
proceeding on the assumption of two doses; however should the scientific data indicate that 
one dose will be sufficient, more vaccines would become available to vaccinate in a shorter 
time those for whom vaccination can be recommended. In case two doses would be needed, it 
is recommendable to give the two doses of the same vaccine, as no clinical data are available 
on  the  interchangeability  of  different  vaccines  against  pandemic  (H1N1)  2009  influenza. 
Also,  if  doses  of  two  different  vaccines  were  given,  it  would  be  difficult  to  link  adverse 
events, which do not manifest themselves shortly after immunisation, to a particular vaccine. 

EN 

8 

   EN 

 
Member  States  will  need  to  take  into  account  in  their  budgets  the  financial  and  human 
resource  implications  of  procuring  and  delivering  the  vaccine.  As  a  planning  assumption  to 
ensure sufficient numbers of healthcare staff, a single vaccinator can vaccinate an estimated 
50 to 100 individuals a day. 

5. 

MONITORING AND EVALUATION OF VACCINATION CAMPAIGNS 

5.1. 

Vaccine safety 

The European Union has a comprehensive and effective monitoring system for reporting on 
and assessing the safety and efficacy of each medicinal product after it has been authorised. In 
addition,  the  European  Medicines  Agency  (EMEA)  has  published  specific  guidance  on  the 
pharmacovigilance  plan  which  forms  part  of  the  risk  management  plan  that  has  to  be 
submitted  with  the  application  for  marketing  authorisation  for  any  pandemic  influenza 
vaccine10. 

It  is  possible  that  when  Member  States  launch  a  vaccination  campaign  against  pandemic 
(H1N1)  2009,  only  limited  safety  data  will  be  available.  Therefore,  Member  States  could 
consider  establishing  additional  enhanced  active  surveillance  for  serious  adverse  events. 
Options could include using sentinel hospitals to screen actively for adverse events following 
immunisation or asking vaccinating doctors or nurses to report to the national authority on a 
weekly  basis,  irrespective  whether  they  have  seen  any  adverse  event  or  not.  Establishing 
protocols for assessing individual suspected cases of adverse events following immunisation, 
in order to ensure best practice, and determining background incidence rates of conditions on 
the list of adverse events of special interest before embarking on vaccination campaigns could 
be other key tools. 

The  activities  described  above  will  be  essential  in  order  to  monitor  closely  any  unexpected 
serious adverse reactions and allow the risk/benefit to be reassessed scientifically if necessary. 
If a vaccine shows serious side-effects, the Commission may — after a scientific assessment 
— vary, suspend or revoke its marketing authorisation. 

Public confidence, and therefore the success of any vaccination campaign against  pandemic 
(H1N1) 2009, will depend on the pharmacovigilance system in the EU working properly. 

5.2. 

Vaccine effectiveness 

Assessing  and  monitoring  the  effectiveness  of  pandemic  vaccines  is  essential  after  vaccines 
are  placed  on  the  market  and  distributed  for  administration.  Although  strain-specific 
pandemic  vaccines  are  expected  to  be  effective  against  pandemic  (H1N1)  2009  influenza, 
early  availability  of  estimates  of  their  effectiveness  will  allow  better  benefit/risk  analysis  if 
adverse  events  are  reported  following  immunisation.  Similarly,  it  will  also  allow  better 
management  of  and  response  to  reports  of  vaccine  failures,  i.e.  of  people  contracting 
pandemic (H1N1) 2009 influenza despite having been vaccinated. 

The  effectiveness  of  the  pandemic  influenza  vaccine  will  be  studied  by  the  vaccine 
manufacturers  in  collaboration  with  regulatory  authorities.  Effectiveness  studies  proposed 
after authorisation will be described in the risk management plan which has to be submitted 

10 

http://www.emea.europa.eu/pdfs/human/pandemicinfluenza/35938109en.pdf. 

EN 

9 

   EN 

 
                                                 
with  the  application  for  marketing  authorisation.  Activities  to  monitor  effectiveness  could 
include  specific  effectiveness  studies,  prospective  observational  safety  studies  including 
effectiveness outcomes and the use of other sources of data such as local networks or sentinel 
physicians. 

The  ECDC  is  working  with  its  partners  (Epiconcept  and  Member  States  in  the  I-MOVE 
partnership11) to extend the mechanism it has developed for seasonal influenza to pandemic 
vaccines. It also maintains close links with its international partners planning to monitor the 
effectiveness of vaccines against pandemic (H1N1) 2009 influenza. 

Should  vaccine  effectiveness  be  found  to  be  poor,  additional  or  alternative  public  health 
measures  could  be  taken  (e.g.  antivirals)  and  further  investigations  could  be  conducted  to 
improve vaccine use or composition. 

11 

More information can be found at: 
http://ecdc.europa.eu/en/publications/Publications/0907_TED_Influenza_AH1N1_Measuring_Influenza
_Vaccine_Effectiveness_Protocol_Case_Control_Studies.pdf. 

EN 

10 

   EN