Bollettino epidemiologico nazionale

Study of Childhood Vaccination Coverage in the Campania Region

Bove C¹, Caiazzo AL², Castiello R³, Citarella A⁴, D’Argenzio A⁵, Ferrara MA⁶, Giugliano F⁷, Morra G⁸, Padula C⁹, Parlato A¹⁰, Parrella R¹¹, Peluso F¹², Simonetti A¹³, Lorenzo E¹⁴, Pagano V¹⁴, Andreozzi S¹⁵, Bucciarelli M¹⁵, Grandolfo ME¹⁵.

¹ASL CE1, ²ASL SA1, ³ASL SA3, ⁴ASL BN, ⁵ASL CE2,  ⁶ASL AV2, ⁷ASL NA5, ⁸ASL NA4, ⁹ASL AV1, ¹⁰ASLNA2, ¹¹ASL SA2, ¹²ASL NA3, ¹³ASL NA1, ¹⁴Regional Epidemiologic Observatory, ¹⁵Istituto Superiore di Sanità.

Introduction

The 1998-2000 Italian National Health Plan, established as one of its objectives achieving a vaccine coverage of at least 95% within the second year of life for the following vaccines: polio; diphtheria, tetanus, and aceullar pertussis (DTPa); hepatitis B (HBV); measles, mumps, rubella (MMR); and Hemophilus influenza type B (HiB).

The activities of monitoring and epidemiologic evaluation of vaccine administration to determine whether objectives have been reached is an important public health function. In addition to measuring overall coverage of vaccines, it is also important to measure whether vaccine administration has been timely. Timeliness is important for the effective control of vaccine-preventable diseases and is a predictor of overall coverage (1); if vaccinations are performed later than recommended, it is highly unlikely that high coverage will be achieved. Timeliness is also important with respect to prevention of disease; the schedule for administration of these vaccines takes into account the ages at which the risk of contracting the disease is greatest.

Most vaccine coverage studies concentrate on relatively large geographic areas and do not generally provide estimates of more local coverage. However, even in areas where overall vaccine coverage exceeds recommended levels, it is important to understand whether the potential for epidemic spread exist at local level (2) as a result of sub-optimal vaccine coverage.

To obtain estimates of coverage and timeliness of vaccines at the district level, a sample survey on vaccination coverage was conducted in 2000-2001 by the Campania Region, coordinated by the Epidemiology and Prevention Units within the Local Health Agencies of the region with consultation from the Istituto Superiore di Sanità. The objective was the estimate the vaccine coverage at a defined age, in each of districts of the Local Health Agencies of Campania.

Materials and Methods

From the population registries maintained in each commune, the first 100 births occurring in each district occurring after 30 of June 1998 were identified. This sample size guaranteed a precision of 6% around the estimated prevalence of 90%. In collaboration with the maternal-child health units and the public prevention units, of each district, the history of vaccination (dates of polio and measles-containing vaccines and whether the child had been received the DTPa, HBV, and HIB vaccines from the vaccine registry; when information was missing or incomplete, a more in-depth investigation was undertaken (telephone call to the mother, a postcard asking the family to contact the study coordinator, and a home visit) to determine whether the vaccines had been administered in the private sector or to obtain information not available from the district records. At the beginning of the study (late 2000), all of the children were at least 24 months old. To evaluate whether the vaccines had been administered according to the vaccine calendar, the percentage who had received the first OPV within 4, 7, and 12 months, the second OPV within 7, 12, and 24 months, and the third OPV within 15, 18, and 24 months. For measles, the percent vaccinated by 15, 18, and 24 months was calculated. Data analysis was conducted using Epi Info. Estimates of vaccine coverage and 95% confidence intervals were calculated at the levels of the local health agencies and for the region, taking into account the relative population of each of the districts and local health agencies, respectively.

Results

Results are reported for all 113 districts of the 13 local health agencies of Campania. For the cohort born in 1998, the vaccine coverage was 95.8% for OPV3, 96.0% for DPTa3, 95.9% for HBV3, 21.4% for HIB3, and 65.0% for vaccines containing measles antigen (Table 1). Coverage higher than 95% for the first and third doses of polio vaccine were seen in 96% and 79% of the districts, respectively.  Suboptimal coverage for the third polio dose (85-89% coverage) was seen in 8% of the districts.  With respect to delays in vaccine administration, in 39% of the districts, 90% of the children had received the first OPV within 4 months, while in 3%, coverage was lower than 70%. For the third dose of OPV, 37% of the districts had coverage of 50% or less within the 12th month of life; none had coverages over 90% and 25% had coverages between 70 and 90% (Figure 1).

The coverage for DTPa and HBV were similar to that for OPV. With respect to HIB vaccine, which had been only recently introduced for the cohort of infants studied, only 4% of the districts reported a three-dose coverage greater than 70%.

In addition, in 23% of the districts, more than 85% coverage with measles-containing vaccines (usually trivalent vaccine) was observed, while in 22%, the coverage was less than 50%.

Conclusions

The vaccine coverage for the polio, DTPa and hepatitis B vaccines was excellent overall, although in a small number of districts in specific local health agencies, suboptimal levels of immunization persist. With respect to measles, mumps, and rubella, additional efforts are needed in the majority of districts if the objective of 95% coverage is to be achieved and spread of these diseases is to be reduced. Additional catch-up efforts will be needed to achieve such coverage, which can be done at the time of other mandatory vaccines (the fourth doses of polio and DT and the when hepatitis B is administered at the age of 12 years.

Another issue raised by this study that requires further efforts on the part of health services concerns the late administration of vaccines. This in part is due to an incorrect interpretation of the vaccine calendar (for example, for the first doses, “within the third month of life” should be interpreted as within 60 rather than 90 days of age. An additional problem is operational issues related to actively finding children who are behind in receiving vaccines, resulting in the fact that 38% of the districts had failed to achieve a 50% coverage for OPV3 within the 12th month of life.

Because delay in vaccination is often associated with poor socioeconomic status, and such status is also a risk factor for earlier infection, it is clear that these delays need to be significantly reduced to prevent the complications of illnesses such as pertussis and hemophilus contracted during the first year of life.

With respect to polio control, the cycle consisting of two doses with IPV and the last two with OPV require rigorous adherence to the vaccine calendar in order to prevent temporary deficitis in herd immunity. Such spread is a possibility in Italy as a result of immigration from countries where polio is still occurring.

References:

1.-Bolton P, Hussain A, Hadpawat A, Holt E, Hughart N, Guyer B. Deficiencies in current immunization indicators. Public Health Rep 1998; 113:527-32.

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

Editorial note:

This study has three relevant aspects:

1. It evaluates coverage at district level

2. It takes into account the timing of vaccination, an important indicator

3. It represents a collaboration involving all the local health agencies of a large region.

Each local health agency has the capacity to evaluate its status regarding the national vaccination plan objectives, to identify possible critical situation, and compare itself with other agencies that have similar organizational and programmatic settings.

Given the difficult socioeconomic situation in many areas of Campania, the positive finding that emerges from this study is that the services of epidemiology and prevention, maternal-child health, and public prevention have succeeded in reaching a major objective of the health system: to reduce the health effects of social inequality.

It would be desirable to repeat similar studies in other regions, possibly using the software ARVA5 developed for use with the vaccine register that is being distributed free of charge to all the local health agencies that request it.