Optimizing Immunization Schedules

Overview of process and application to

pneumococcal conjugate vaccines (PCV)

Paul Fine London School of Hygiene & Tropical Medicine

Optimizing Immunization Schedules WHY are we working on this?

“SAGE recognized the importance and timeliness of reviewing the scientific and operational basis for the choice of the optimal schedule for childhood immunization. More than 20 years have passed since the “EPI schedule” of 6, 10 and 14 weeks for DTP-OPV and 9 months for measles vaccine was introduced, and more information has accrued, together with the development of improved techniques for assessing immune responses. There was recognition that immunization schedules in use today vary greatly around the world, and it is unlikely that a single, uniform immunization schedule would suit all countries. WHO should aim to provide countries with advice on the parameters to be considered when they select a schedule. There was unanimous support for a new review of the evidence base, and agreement that changes in schedule are not appropriate without strong evidence to demonstrate benefit. It has also been stressed that it is difficult to design ONE schedule for ALL countries as there are differences in epidemiology, health infrastructure and resources. In developed countries these discussions take place at national level based on local data however, low resource countries often rely on decisions made by others".

WER, January 2006

•  The goal is a process for decision-making at country or regional level;

•  this will be continuous, as new vaccines are developed and as epidemiological circumstances evolve;

•  different schedules will probably be appropriate for different epidemiological areas of the world;

•  incremental gains of a new schedule need to be substantial to deserve introduction and;

•  need to look at all vaccines, not only one, and to consider other relevant factors

Optimizing Immunization Schedules WHAT does this mean ?

Optimizing Immunization Schedules WHAT evidence should be considered?

DISEASE Epidemiology and clinical

characteristics

VACCINE Effectiveness & Safety

Availability Regulatory issues

OPERATIONAL & HELTH SYSTEMS

Cold chain & logistics Health systems opportunities

Acceptability Challenges for implementation

ECONOMICS & AFFORDABILITY

Costs, cost effectiveness Opportunity costs

Optimizing Immunization Schedules WHAT progress to date * ?

ANTIGEN Epidemiology Vaccine Economics and affordability

Operational & health system

Pertussis "Rapid" review

PCV West Africa (Burkina Faso, The Gambia) Kenya, Israel

Systematic review

Comparison of models and CEA tools West Africa model, initial ICEA

Rotavirus Cases & deaths finely stratified < 3 years of age

Comparison of models and CEA tools

Hib Systematic review (ongoing)

* also: fundraising for : Rota, Diphtheria, Hep B, Tetanus,…..

Optimizing Immunization Schedules Global review of rotavirus data by

age and region*

Data obtained so far: –  Numbers of children by age at event in weeks –  40+ datasets (at least 2 from each WHO region) –  Size of datasets: median: 801 events, IQR: 386 to 1096

Type of event: most studies are of hospital admissions + a few studies of community cases + a few of deaths but numbers very small

* Courtesy of C Sanderson et al and the WHO regional surveillance networks

0%

20%

40%

60%

80%

100%

0   4   8   12   16   20   24   28   32   36   40   44   48   52  

Age in weeks

RVGE in children: Vellore, India 2002-7

cum % of community cases of RVGE in children <3y, urban slums, Vellore

cum % of hospital cases of RVGE in children <3y, Vellore

Sources:    

Bannerjee  et  al  2006  

Kang  et  al  2009    

% o

f cum

ulat

ive

inci

denc

e to

age

3 y

rs

0%

20%

40%

60%

80%

100% 0%

20%

40%

60%

80%

100%

0   4   8   12   16   20   24   28   32   36   40   44   48   52  

% c

over

age

% o

f cum

. inc

iden

ce

% u

nvac

cina

ted

Age in weeks

RVGE in children vs vaccine coverage: Vellore, India 2002-7

cum % of community cases of RVGE in children <3y, urban slums, Vellore cum % of hospital cases of RVGE in children <3y, Vellore DTP1 (mean for India) DTP2 (mean for India) DTP3 (mean for India)

Sources:    

Bannerjee  et  al  2006  

Kang  et  al  2009    

DHS  2009  

% o

f cum

ulat

ive

inci

denc

e to

age

3 y

rs

6 15 32

0%

20%

40%

60%

80%

100% 0%

20%

40%

60%

80%

100%

0   4   8   12   16   20   24   28   32   36   40   44   48   52  

% coverage

% o

f cum

. Inc

iden

ce

% u

nvac

cina

ted

Age in weeks

RVGE in children vs vaccine coverage by wealth quintile

Vellore, India 2002-7

cum % of community cases, urban slums, Vellore cum % of hospital cases, Vellore DTP1 (mean for India): Q5 (poorest) DTP1: Q4 DPT1: Q3 DTP1: Q2 DTP1: Q1 (least poor)

Sources:    

Bannerjee  et  al  2006  

Kang  et  al  2008  

DHS  2009  

% o

f cum

ulat

ive

inci

denc

e to

age

3

yrs

6 15 32

Optimizing Immunization Schedules PCV as example

“METHODS” experts Epidemiology, systematic reviews, models and cost-

effectiveness analysis

Initial small group discussion on questions and evidence to consider.

Conference call(s) to review process and suggest data and synthesis issues

Ad hoc consultation to review successive drafts and identify additional issues

Contents expert review of “final” report

+

SAGE

“CONTENTS” experts PCV Vaccine & Spn disease

QUIVER Committee

Optimizing Immunization Schedules Today's session

PREVIEW on:

"   Systematic review - PCV effectiveness as a function of schedule

"   Model - PCV schedules & CEA in West Africa scenario

"   DRAFT website to share results

Optimizing Immunization Schedules SAGE advice is important:

•  Does this approach address SAGE’s recommendations ?

•  What are the priority vaccines and epidemiological scenarios to include in future assessments ?

•  SAGE endorsement to assist fundraising