M. G. Panico¹, N.M. Trinchese¹, B. Serpieri², F. Attena^3
1 Servizio di Epidemiologia e Prevenzione, Azienda Sanitaria Locale Napoli 4, Italy
² Distretto Sanitario 75, Azienda Sanitaria Locale Napoli 4, Italy
³ Istituto di Igiene e Medicina Preventiva, Seconda Università di Napoli, Italy

Italy’s health ministry introduced changes to the immunisation schedules for children on 7 April 1999, including immunisation against poliomyelitis. The changes included the replacement of the first two childhood doses of oral poliomyelitis vaccine (OPV) with inactivated-injectable poliomyelitis vaccine (IPV). This measure was introduced after the risk of acquiring wild poliomyelitis had been compared with the risk of developing vaccine associated paralytic poliomyelitis (relative risk 0/10). The last indigenous case of poliomyelitis in Italy arose in 1983 and the last imported case occurred in 1988 (1). This communication describes how the new law has affected the rate of polio vaccinations in an area of Naples corresponding to the Azienda Sanitaria Locale (ASL NA4) made up of 11 health districts, where 7500 babies were born in 1998.

The new schedule had to be implemented 15 days after its publication in the Italian Official Gazette. Consequently, the IPV vaccine had to be readily available in sufficient amounts throughout the country, although it had not been used before. IPV was registered and marketed in Italy by one company only, in the form of a monovalent vaccine and a pentavalent vaccine, which also contains vaccines against tetanus, diphtheria, pertussis, and Haemophilus influenzae type b (Hib); three of these are compulsory in Italy for all infants and two are voluntary. Stocks of vaccine on the Italian market were immediately found to be insufficient, especially for the monovalent vaccine.

In Italy, each local health authority (ASL) is autonomously in charge of the purchase of vaccines. To obtain the monovalent preparation it was necessary for each ASL to import the vaccine from other countries where it was marketed and available. In these countries, the monovalent vaccine available had a different packaging and presentation and was therefore considered not to be in conformity with the vaccine licensed in Italy. The procedure provided by Italian law for the import of medicines not registered in the country required the agreement of the manufacturer and consent from the patient. As a result of this the supply of vaccines in several health centres was disrupted, which caused confusion among the population. As a result, vaccination coverage against poliomyelitis declined sharply.

The table shows data on vaccinations performed in five of the 11 health districts in our local health authority. The vaccination coverage rates calculated were based on the first dose of vaccine (administered in the fourth month of life). All children (2022) born in the first six months of 1998 and all children (1840) born in the first six months of 1999 were compared; the last dates of inclusion were 31 October in 1998 and 1999. Coverage of children born in 1998 increased slightly between the first and second quarters, following a constant upward trend seen for the past few years (data not reported in the table), albeit at a lower level than the national average (86.0% v 94.6% in children aged 12 to 24 months, in 1998, for the first three doses of OPV) (2). In the comparison of children born in the first and second quarters of 1999, between which OPV was replaced by IPV, immunisation coverage fell from 80.5% to 35.3% (table). This was associated with a reduction in the coverage of other compulsory vaccinations, which is also believed to have affected other areas in Italy. We do not know how many of the subjects who missed their first dose of IPV will be vaccinated at a later date.

Table. Number of children receiving their first dose of poliomyelitis vaccine in the first half of 1998 (OPV) and 1999 (IPV) in five districts of the Local Health Authorities of Naples

Number vaccinated/total number(%)

1998

1999

Period covered

First quarter

737/962 (76.6)

799/993 (80.5)

Second quarter

834/1060 (78.7)

299/847 (35.3)

Total

1571/2022 (77.7)

1098/1840 (59.7)

1. Italian Ministry of Health. Circular No 5. 7 April 1999.

2. Salmaso S, Rota MC, Ciofi degli Atti ML, Tozzi AE, Kriedl P, and the ICONA (Indagine Copertura Nazionale) Study Group. Infant immunization coverage in Italy: estimates by simultaneous EPI cluster surveys of regions. Bull World Health Organ 1999; 77: 843-51.