Bollettino epidemiologico nazionale

Vaccine Coverage Against Hepatitis B among Residents of the Province of Catania Born between 1980 and 1989

*Cuccia Mario,** Guarrera Vito,* Nastri Andrea,*** Siciliano Lucia

*Epidemiology Service, Local Health Authority 3-Catania, Sicily

**Resident, Hygiene and Preventive Medicine, University of Catania

***Specialist, Hygiene and Preventive Medicine

Ten years after the introduction in Italy of mandatory hepatitis B vaccine during the 12th year of life, the Epidemiology Service of the Local Health Authority (ASL) of the Province of Catania (ed. note: one of the 10 provinces of Sicily) decided that a study of vaccine coverage was needed to see if the 95% coverage objective of the National Vaccination Plan for 1999-2000 (1) had been reached. The Plan called for, among other things, the intensification of vaccination activities in areas through active efforts even after 2003, the year in which vaccine among 12-year olds was to be phased out. (Ed. note: infants have been routinely vaccinated in Italy since 1991; the vaccination of 12-year olds was mandated between 1991 and 2003 to ensure more complete coverage of the population.

In the ASL of Catania, as in many of the ASL in southern Italy, anti-hepatitis B vaccination is conducted in middle schools, with students identified from enrollment records (2). (Ed. note:  rather than from population registers, as is the policy in central and northern Italy). Subsequently, the information on vaccination status is placed in a vaccination register.

A previous study (2) conducted in 1993-1994 on the 1981 birth cohort estimated that southern Italy had a suboptimal coverage of 65.1%, but the study did not provide data at regional or provincial level. In 2001-2002, the ASL of Catania therefore conducted a study with the primary objective of evaluating anti-hepatitis B vaccine coverage in each of the 12 districts of the province for all residents born during the ten-year period between 1980 and 1989. In addition, the quality of the vaccine register was evaluated by determining whether children included in the study sample were also in the register.

A total of 149,821 children were identified for potential inclusion in the study. A stratified sample survey was conducted according to EPI guidelines (3); each of the 12 districts constituted a stratum in which 100 children and 10 possible replacements were drawn from local population registers.

Data collection was carried out between October 2001 and April 2002, using a specially developed data collection instrument. Data on vaccination were obtained from the vaccine registers; for those whose names could not be found in the registers or who according to the records had not been vaccinated or had been incompletely vaccinated, home interviews were conducted.

Children were considered vaccinated if they had received at least 3 vaccine doses, with the interval between the first and second doses being less than a year. Only those doses administered prior to September 30, 2001 were considered. The analysis was conducted using Epi Info 6, version 6.04d.

Information was collected on 1200 children of whom 51 were substitutions for children who could not be located (4.2% of the total sample, with a range of 0-9% in the various districts). Overall vaccine coverage weighted on the basis of the target population in each district was 91% (1097/1200; 95% confidence limits 90%-93%). The estimates in the individual districts varied from 79% to 98% (Table). The lowest value was observed in Catania 2, the most socially and economically disadvantaged of the districts. Of note, during 2002, 9 cases of hepatitis B were notified in Catania to the SIEVA surveillance system; the two cases among persons born between 1980-1989 were residents of this district.

Of the 103 children not vaccinated, 48, or 4% of the total study population, received two doses. The percentage of subjects vaccinated with only two doses varied somewhat among districts (Table); the number of non-vaccinated in each birth cohort ranged from a high of 18 in 1980 to a low of 7 in 1989.

The major risk of non-vaccination (odds ratio 2.6, 95% confidence intervals 1.1-5.8) was not being enrolled in the vaccine register. The principal reason for non-vaccination for the 103 who were not vaccinated was also investigated; the most common reason was inadequate vaccination services (52), not attending school (15), being asbsent from school (13), refused (8), transferred (8), presence of contraindications (6), and being HbsAg postive (1). Inadequate services was considered to be the reason when the response given was not attributable to parents’ refusal to have their child vaccinated (either explicit or implicit) but was instead related to problems in the provision of vaccination services (for example lack of information provided to the parents, vaccination not offered at the school attended, or efforts diluted over more than a single school year).

CONCLUSIONS

• The survey highlights the finding that the coverage was higher than expected based on the data for southern Italy for the 1981 birth cohort (2); in five of the districts, the coverage was > 95%.  The discrepancy with the previous study may have resulted from differences between the population in study (Ed. note: the earlier study reports only composite data for 12 provinces in southern Italy) or improvements over time in coverage levels.

• The higher risk of not being vaccinated among those not enrolled in the vaccine register demonstrates some of the limitations in the current system of identifying children in need of vaccination in Catania.

• To better reach the coverage objectives, it would be useful to further study reasons for non-vaccination, including verification, for example, of the correlation between parental educational attainment and vaccination as recently suggested by the national multipurpose survey conducted by the Italian National Statistics Institute (ISTAT) (4).

• Especially in those districts where the estimation of coverage is lower and the risk of infection is higher, a variety of catch-up strategies will be needed based on the situations encountered.

Editorial Note

Stefania Salmaso

Laboratory of Epidemiology and Biostatistics

Istituto Superiore di Sanità, Rome

The current Italian policy of required hepatitis vaccination for twelve-year-olds expires in 2003, when those who were born in 1991 and vaccinated during the first year of life will reach the age of 12 years. For this reason, this survey of the vaccine coverage among adolescents presented in this study is highly opportune. Specifically, this study provides data useful for the prevention of hepatitis B, including the quantification of susceptible individuals who have now been protected from this serious infection, the determination of the reasons, or at least the factors, associated with failure in the provision of vaccination, and estimation of the reduction in hepatitis B cases that can be expected in the near future.

The results of this study show that there was considerable variation from area to area in coverage, from 79% to 98%, probably linked with efforts to provide vaccine to the target population, and that approximately half of those who were not vaccinated failed to receive vaccination because of problems with service provision rather than with unwillingness to be vaccinated. These findings suggest that a series of opportunities exist for improving vaccine coverage efforts.

The evaluation of vaccine services to date has almost always been based on the proportion of children vaccinated, and coverage's in excess of 75% of the eligible population are often considered a success. However, epidemiology reminds us that sub optimal coverage may result, in the long run, in failure to fully attain the many advantages offered by vaccination, especially for those diseases transmitted by person-to-person contact. Attention should currently focus not on the number of children vaccinated but on the number not vaccinated and on attempts to identify and vaccinate these children, such that the rights every child in Italy has to be vaccinated can be fully realized. This study done of children 12 years of age is further useful in allowing us to estimate the likely success of programs designed to provide other vaccinations to this age group and to identify operative issues with such programs.

References

1.   Piano Nazionale Vaccini .G.U.R.I. n.176 del 29/07/1999, Serie generale, Supplemento n.144.

2.   Stroffolini T., Caldea L., Tosti M.E., Grandolfo M., Mele A. Vaccination campaign against hepatitis B for 12-year-old subjects in Italy. Vaccine 1997, 15: 583-586.

3.   Expanded programme on immunization. “The Epi coverage survey” 1991, Who/Epi/mlm/91.10.

4.   Indagine multiscopo “Condizioni di salute e ricorso ai servizi sanitari”, ISTAT 2002.