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Eurosurveillance, Volume 3, Issue 10, 01 October 1998
Surveillance report
ESEN : a comparison of vaccination programmes Part one: diphtheria

Citation style for this article: Lévy-Bruhl D, Pebody RG, Veldhuijzen I, Valenciano M, Osborne K. ESEN : a comparison of vaccination programmes Part one: diphtheria. Euro Surveill. 1998;3(10):pii=87. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=87
 

Daniel Lévy-Bruhl (co-ordinator), RNSP/CIDEF, France
Richard Pebody, NPHI/EPIET, Finland
Irene Veldhuijzen, RIVM, Netherlands,
Marta Valenciano, RNSP/EPIET, France
Kate Osborne (ESEN Project Co-ordinator), CDSC, England & Wales
from data provided, on behalf of the ESEN project, by :

Anne-Marie Plesner, SSI, Denmark
Mary Ramsay, CDSC, England and Wales
Wolfgang Vettermann / Doris Altmann, RKI, Germany
Stefania Salmaso, Christina Rota, ISS, Italy
Richard Pebody, NPHI, Finland
Martine Le Quellec Nathan, DGS / Nicole Guérin, CIDEF, France
Marina Conyn-van Spaendonck, RIVM, Netherlands
Patrick Olin, Victoria Romanus, SIIDC, Sweden


Introduction

The aim of the European Sero-Epidemiology Network (ESEN) is to coordinate and harmonise the serological surveillance of immunity to vaccine preventable diseases in eight countries in Europe (Denmark, England, France, Germany, Italy, the Netherlands, Finland, and Sweden). It was established in March 1996 under Biomed II programme of the European Community and is coordinated by the Public Health Laboratory Service Communicable Disease Surveillance Centre (CDSC) in London. The specific objectives and the various workpackages of the project have been described previously (1). One of the workpackages - on the descriptive analysis of the differences in vaccination programmes, current and past incidence of disease, and current and past vaccination uptake - has been undertaken for ESEN under the coordination of the Centre International de l’Enfance et de la Famille and the Réseau National de Santé Publique in France. This paper presents the results of the descriptive analysis of diphtheria, which includes the characteristics of the immunisation programme, vaccine coverage, and disease specific information. Further papers will present the descriptive analysis of pertussis and the three diseases - measles, mumps, and rubella (MMR) - covered by the MMR vaccine.

Methods

The data were collected by a questionnaire that was agreed at a meeting of national ESEN project coordinators who were responsible for the completion of the questionnaire within their own country, involving, when needed, other national experts. The questionnaires were completed during the first trimester of 1997 by all eight participating countries and were analysed by a working group that included representatives from several countries. A report was prepared and circulated at various stages for validation by the national project coordinators.

Programme characteristics and service delivery

Two categories of country were identified (table 1):

- In Denmark, Finland, England and Wales, the Netherlands, and Sweden, vaccination is the responsibility of the public services. Vaccination is free of charge and is not compulsory. Active follow up procedures are used to ensure high coverage early in life.

- In France and Italy, the private sector is largely responsible for vaccination and part of the cost may remain at the recipient’s expense. Some vaccinations are compulsory and the vaccination status of children is not checked systematically before they start school, but in France, some municipalities check the vaccination status of children aged 18 to 24 months. In Germany most immunisation activities are carried out in the private sector.

Table 1 :  Programme characteristics and vaccination coverage assessment in eight countries for diphtheria, pertussis, and measles, mumps, and rubella

 

Germany

Denmark

Great-Britain

Finland

France

Italy

Netherlands

Sweden

Legal status (1)

All R

All R

All R

All R (diphtheria: C in the army)

Diphtheria: C Others: R

Diphtheria: C
Others: R

All R

All R

% vaccinations in public sector (2)

< 5 years old

5%

99%

> 99%

99%

15%

Variable

100%

100%

> 5 years old

20%

99%

> 99%

ND

ND

ND

100%

100%

Active stimulation of full coverage (3)

No

FU (MMR)

RB / FU / TD

RB

In some municipalities or districts

RB / FU in some regions

RB / FU / TD

No

Incentives for vaccination providers

No

No

Yes

No

No

No

No

No

At least yearly coverage assessment

No

Yes

Yes

No (every 2-3 years)

Yes

3 large surveys since 1980

Yes

Yes

Vaccination coverage indicator (4)

NA

Vaccinated / population data

Vaccinated / population data

Vaccinated / registered children

Vaccinated / health certificates

NA

Vaccinated / population data

Vaccinated / health records

Validation mechanism of coverage measurement

NA

Double check at all levels

Audit / cross-checking

Cluster surveys

Cluster surveys

Cluster surveys

Cluster surveys

During pertussis vaccine trial

Estimation of accuracy of coverage measurement

NA

Very accurate

Very accurate

Very accurate

Précis

C: accurate R : not accurate

Very accurate

Very accurate

 

(1) R = recommended : C = compulsory
(2) ND = no data
(3) RB = registration at birth ; FU = follow up by invitations ;  TD = tracing of defaulters (4) NA = Not applicable

Vaccination coverage assessment

Among the eight countries, only Germany has no routine vaccination coverage assessment (table 2). All the others have at least one assessment per year except in Finland where cluster surveys are carried out every two to three years on samples of child health records. Participating countries have tested the validity of their assessments through either a regular validation procedure or occasional studies, mainly cluster sample surveys. All but France and Italy concluded that their assessments are accurate. In France, the assessment is not completely accurate because the return of health certificates is incomplete. In Italy, assessment of coverage at the national level is considered to be unreliable particularly for the vaccinations that are not compulsory. For this reason, surveys of vaccine coverage using cluster sampling are also performed.

Table 2: Diphtheria immunisation schedules in eight countries

 

Germany

Denmark

Finland

France

Great-Britain

Italy

Netherlands

Sweden

Age at 1st dose

3 m

3 m

3 m

2 m

2 m

3 m

3 m

3 m

No of doses < 2 years

4

3

3

4

3

3

4

3

Total No of doses

6

4

5

7

5

4

6

4

Age when last booster offered

11-15 years + booster every 10 years

5 years

11-13 years + booster every 10 years

16-18 years + military recruits

15 years

5-6 years + booster every 10 years (see below)

9 years

10 years

Age of shift from high (D) to low (d) dose

6 years

D only

10 years

d for adults

10 years

7 years

4 years

D only

Recent changes in response to NIS epidemic

10 yearly boosters in adults

1996 : booster at 5 years Travellers to endemic areas

1989-90 : catch-up campaign Booster : - at 11-13 years - > 40 years - military recruits - travellers to endemic areas

Adults travelling to endemic areas

1994 : Td* replaced T** for school leavers

Td booster recommended every 10 years, but coverage not measured

Travellers to endemic areas

Travellers to endemic areas

Cumulative No of cases since 1990

32

0

20

0

28

4

2

0

 

* Td: Tetanus-diphtheria vaccine
** T: Tetanus vaccine

Diphtheria

1- Immunisation schedule

All participating countries introduced diphtheria immunisation about 50 years ago. Table 2 compares the current immunisation schedules. The first dose is usually administered at either 2 or 3 months of age. The total number of diphtheria doses received by a child in the first two years of life is three or four, the total number of doses (including boosters) after two years of age and the age of the last dose varies widely (five years to lifelong ten yearly boosters). The age at which low dose (d) replaces high dose diphtheria vaccine (D) also varies.

Many countries have added extra doses to their immunisation schedule following the recent diphtheria epidemic in the Newly Independent States (NIS). Responses differ and the schedules are now more heterogeneous than during the 1980s, when five of the eight countries gave the final booster at or before 2 years of age. All countries now have a booster at least for children of school age and, with the exception of Germany (which has introduced 10 yearly boosters in adults), a booster dose for travellers to risk areas. Finland initiated a mass vaccination campaign in 1989-90 targeted at adults based on the results of serosurveys that indicated low antibody levels in those aged over 40 years.

2 - Vaccination coverage

Only data for coverage with primary series can be compared due to variability in booster policies.

From 1970 onwards, the Netherlands, Denmark, Finland, and Sweden have had high coverage rates, ranging between 95% and 100%. In England and Wales coverage has increased from 80% in the early 1970s to 96% in 1996. In France, coverage figures for three doses have been available only since 1990, showing coverages over 95%. In Italy the coverage was over 98% in the most recent cluster survey conducted in 1991 in seven regions. In Germany, no coverage data are available.

France and the Netherlands have no official contraindications for diphtheria vaccination and the only contraindication in the other countries is a severe reaction to a previous dose. This seems to have had a negligible effect on vaccine coverage, affecting less than 1% of those eligible for vaccination.

3 - Surveillance and epidemiology

In all participating countries diphtheria is a notifiable disease and laboratory confirmation is required.

Diphtheria was virtually eliminated from the Netherlands, Denmark, Finland, and Sweden in the early 1970s, with almost no cases notified with probably exhaustive surveillance. During the same period, the situation in England and Wales was similar, with incidences below 1 per 10 million inhabitants since 1975. In the 1970s, Germany and France reached a high level of disease control with rates of less than 10 per 10 million, acknowledging the less reliable surveillance data in Germany. Only Italy had a higher incidence, which only fell below 10 per 10 million during the early 1980s.

Diphtheria is now well under control in all the participating countries. In Denmark, France, and Sweden no cases have been notified since 1990. During the 1990s, a number of sporadic cases have been reported from the other countries, mainly linked to the large outbreak in the former Soviet Union. In Finland, all cases were linked to travel to the NIS and no secondary transmission has occurred. In Germany at least eight of the 13 cases diagnosed between January 1994 and June 1996 were linked to the NIS outbreak. In these two countries, 29 of the 32 cases (91%) notified between 1993 and 1996 were adults aged over 20 years. All but one of the cases reported from England and Wales were also imported or import related, mainly related to travel to south east Asia.

Discussion

The experience gained from diphtheria vaccination shows that all countries participating in ESEN have the infrastructure and resources to achieve high vaccine coverage in children. This has resulted in a uniform high level of control of the disease, even with wide variations in vaccination schedules, particularly with regard to the age at the last dose. The most important factor for disease control appears to be coverage with the primary series. This is illustrated by the situation in the 1970s, when those countries with high coverage had eliminated domestic transmission, even with a schedule including only two doses before the age of 1 year and a total of three doses, as in Denmark until 1996.

Adult immunity may have been important in the resurgence of the disease and recent studies have shown that up to a half of adults in some western European countries have low levels of or undetectable diphtheria antibodies (2,3). Comparison between countries, however, is hampered by the use of different methods and thresholds, justifying the standardisation process undertaken under the ESEN project (4). Despite increasing contact with epidemic countries, domestic transmission has not resumed in Western Europe even in those countries with few doses in the immunisation schedule. Most recently reported cases were adults linked epidemiologically with cases from epidemic/endemic countries. It may be that high coverage rates in childhood result in a herd immunity that is sufficient to prevent transmission (5,6). The high proportion of cases among adults in the few recently notified sporadic cases in the countries under study probably reflect a combination of more frequent exposures of adults to cases from epidemic/endemic countries at home or through travel to these areas, the higher infectious dose due to close personal contact (such as kissing), and the higher susceptibility in adults. The immunisation status of older people should be checked and updated before they travel to areas where diphtheria is still endemic.


References

1. Osborne K, Weinberg J, Miller E. The European Sero-Epidemiological Network. Eurosurveillance 1997; 2: 29-31.

2. Plotkin SA, Mortimer EA. Diphtheria toxoid. In: Vaccines. second edition. Philadelphia: WB Saunders, 1994.

3. Galazka AM, Robertson SE. Immunisation against diphtheria with special emphasis on immunisation of adults. Vaccine 1996; 14: 845-57.

4. Galazka AM. Diphtheria: the immunological basis for immunisation. Geneva: World Health Organization, 1993. WHO/EPI/GEN/93.12.

5. Galazka A, Tomaszunas-Blaszczyk J. Why do adults contract diphtheria? Eurosurveillance 1997; 2: 60-3.

6. Fine PEM. Herd Immunity: history, theory, practice. Epidemiol Rev 1993; 15: 265-302.



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