Original article
The impact of changing BCG coverage on tuberculosis incidence in Swedish-born children between 1969 and 1989

https://doi.org/10.1016/0962-8479(92)90149-EGet rights and content

Abstract

In April 1975, the mass vaccination of newborns against tuberculosis was replaced by selective vaccination of groups at risk. BCG coverage fell from more than 95% before 1974 to 1.8% between 1975 and 1982 and thereafter reached an average of 13.7% up to 1989. The cumulative incidence of tuberculosis before 5 years of age was estimated among children born in Sweden during periods of high, low and moderate increasing BCG coverage. The incidence figures per 100 000 children was 0.8, 3.9 and 2.9, respectively, for children born to Swedish parents and 2.6, 39.4 and 13.2, respectively, for those born to foreign parents. The observed incidence of tuberculosis among non-BCG vaccinated children born to Swedish parents was within the expected limits given by a prognostic model based on the natural change of the risk of infection. The effectiveness of the selective BCG vaccination programme, which was intensified after 1981 for the second generation of immigrants, was estimated to 0.82 (95% confidence interval 0.38, 0.95) assuming that there was no change of the risk of infection for children born to foreign parents over the period studied. From April 1975 to December 1989, tuberculosis was notified in 85 children born in Sweden during the same period, 7 of them were BCG vaccinated and 78 non-vaccinated, 45 were symptomatic, 3 of them with disseminated tuberculosis.

Résumé

Au mois d'avril 1975, la vaccination de masse des nouveau-nés contre la tuberculose a été remplacée par la vaccination sélective de groupes à risque. L'étendue de la pratique du BCG a baissé de plus de 95% avant 1974 à 1,8% entre 1975 et 1982, et ensuite a atteint une moyenne de 13,7% jusqu'à 1989. L'incidence cumulée de tuberculose avant l'âge de 5 ans a été estimée chez les enfants nés en Suède pendant des périodes de pratique du BCG haute, basse et modérément croissante. Les chiffres d'incidence pour 100000 enfants étaient respectivement de 0,8, 3,9 et 2,9 chez les enfants nés de parents suédois, et respectivement de 2,6,39,4 et 13,2 chez les enfants nés de parents étrangers. L'incidence observée de tuberculose chez les enfants non-vaccinés par le BCG et nés de parents suédois était dans les limites attendues sur la base d'un modèle pronostique fondées sur l'évolution naturelle du risque d'infection. L'efficacité du programme de vaccination BCG sélective, qui a été intensifié après 1981 pour la deuxième génération d'immigrés, a été estimée à 0,82 (95%: intervalle de confiance 0,38, 0,95), en supposant qu'il n'y ait eu aucun changement dans le risque d'infection pour les enfants nés de parents étrangers pendant la période étudiée. Du mois d'avril 1975 jusqu'en décembre 1989, la tuberculose a été notifiée chez 85 enfants nés en Suède pendant la même période, dont 7 étaient vaccinés avec le BCG et 78 non-vaccinés; 45 étaient symptomatiques dont trois porteurs d'une tuberculose disséminée.

Resumen

En abril de 1975, la vacunación de masa de los recién nacidos contra la tuberculosis fue reemplazada por una vacunación selectiva de grupos de alto riesgo. La cobertura de BCG disminuyó de más de 95 % antes de 1974 a 1,8 % entre 1975 y 1982 y enseguida ha alcanzado un promedio de 13,7 % hasta 1989. Se estimó la incidencia acumulada de tuberculosis antes de los 5 años de edad en niños nacidos en Suecia durante los períodos de alta, baja y moderadamente creciente cobertura de BCG. Las tasas de incidencia por 100 000 niños fueron 0,8, 3,9 y 2,9 respectivamente para los niños nacidos de padres suecos y 2,6, 39,4 y 13,2 respectivamente para los de padres extranjeros. La incidencia de tuberculosis observada en los ninos no vacunados de padres suecos se encontraban dentro de los límites esperados en base a un modelo pronóstico fundado sobre la evolución natural del riesgo de infectión. La eficacia del programa de vacunación BCG selectiva, que fue intensificada después de 1981 para la segunda generación de inmigrantes fue estimada en 0,82 (0,38 - 0,95 con un intervalo de confianza a 95%), suponiendo que no hubiera habido ningún cambio en el riesgo de infección para los niños de padres extranjeros durante el período estudiado. De abril de 1975 a diciembre de 1989, la tuberculosis fue notificada en 85 niños nacidos en Suecia durante el mismo período, de los cuales 7 estaban vacunados con BCG y 78 no vacunados; 45 eran sintomáticos, de los cuales 3 presentaron una tuberculosis diseminada.

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