Bollettino epidemiologico nazionale

Sentinel Pediatric Surveillance in Italy: Results from 2000

Marta Ciofi degli Atti for the coordinating committee, SPES Coordinating committee, SPES: Raffaele Arigliani; Vincenzo Calia; Patrizia Carbonari; Francesco Cobianchi; Paolo D’Argenio; Stefano Del Torso; Milena Lo Giudice; Sabrina Lostumbo; Vitalia Murgia; Silvana Parroccini; Alberto Eugenio Tozzi; Stefania Salmaso; Giovanni Vitali Rosati

In January 2000, a national sentinel surveillance system for vaccine preventable diseases was launched in Italy which was based on pediatricians who work under contract for the public Local Health Agencies. The objective of the surveillance was to provide timely and accurate estimates of the trends of these diseases and the impact of vaccine programs on these trends.

Participation is voluntary; the pediatricians who participate are requested to provide the number of patients in their practice and their age distribution. The case definitions for measles, mumps, rubella, pertussis, and chickenpox are entirely clinical. For bacterial meningitis and congenital rubella, which are usually diagnosed in hospital settings, the physicians are asked to provide laboratory confirmation where available.

Each month the participating pediatricians notify via web or fax if they have collected surveillance data during that month and how many cases of each of the diseases they observed. Feedback is provided through posting on the website www.spes.iss.it.

In 2000, an average of 468 pediatricians participated every month (range 404-576). The number of children enrolled in their practices is estimated at 384,000 children under the age of 14 years, representing 5% of the national population in this age group.

The most frequently reported disease was chickenpox, followed by mumps ( 53 and 19 cases per 1000, respectively). Pertussis, rubella, and measles all had reported incidences less than 10/1000. These estimates are between 4-10 times higher than those obtained through the routine notification system (SIMI, data updated 10/3/2001) (Table 1), with major differences in the two systems between north and south. In the north, the estimates obtained through the sentinel surveillance system were similar to those obtained through routine surveillance for measles but were 3-8 times higher for other diseases. In the south, by contrast, the differences between the two sources of data ranged from 9 times higher for the sentinel system for rubella to 24 times higher for measles. Also of note, routine notification data are available for only a limited number of the regions in the center and south.

Chickenpox and mumps had similar incidence rates in the various parts of the country, while pertussis, rubella, and measles were generally more frequent in the center and south than in the north. Geographic differences in incidence were greatest for measles, the incidence in the center and south was ten times higher than in the north.

The percentage of cases occurring in vaccinated children was 18% for rubella, 21% for measles, and 59% for mumps. While the percent of measles and rubella cases who had been vaccinated declined with age, for mumps the values remained more stable, ranging from 62-26% for children 1-9 years of age and 43% for those 10 years and over. The information on type of vaccine was noted for 3763 of 4292 vaccinated (88%), 74% of whom received vaccine containing the Rubini strain and 18% the Urabe strain.

In addition to the above findings, 2 cases of congenital rubella were reported, yielding an incidence of 0.06 per 1000 newborns. Nine bacterial meningitis cases were reported, of which 3 were caused by meningococcus and two by pneumococcus. The incidence rates of meningococcal and pneumococcal meningitis in the first five years of life were 2.1/100 and 1.4/100, respectively.

From the 2000 data, a number of important conclusions emerge:

- The sentinel surveillance system is considerably more sensitive than that based on obligatory notification.

- The higher incidence of pertussis, measles, and rubella in the central and south are probably attributable to the lower vaccine coverage in these areas.

- Assuming that the vaccine coverage for measles, rubella and mumps are identical (in 1998, an average of 94% of children vaccinated against measles had received a trivalent MMR vaccine) and that the vaccine coverage is higher for more recent cohorts, the high percentage of vaccinated mumps cases in the 1-9 year age group indicates a reduced efficacy of this vaccine compared with that obtained for measles and rubella.

- In particular, the elevated percentage of children with mumps who were vaccinated with the Rubini strain is in line with evidence from field studies from other countries demonstrating its low efficacy.