Aşı epidemiyolojisi: aşı etkililiği için epidemiyolojik çalışma tasarımları

Öz

Yeterli etkinliği gösterilmiş ve lisans almış bir aşının bir toplumda uygulanmasıyla ilgili hastalıktan korunma düzeyi ideal olmayan saha koşullarında, gözlemsel epidemiyolojik çalışmalarla belirlenen ‘aşı etkililiği’ ile ölçülür. Toplumda ilgili hastalık insidandaki azalmanın uygulanan aşılamadan mı, aşılama dışındaki nedenlerden mi kaynaklandığının belirlenmesi için, aşı etkililiği sürveyansın bir parçası olarak rutin izlenmelidir. Bu nedenle aşı etkililiği çalışmaları halk sağlığı eylemleri için önemli bir role sahiptir. Kohort ve olgu kontrol çalışmaları gibi klasik gözlemsel epidemiyolojik çalışmalara alternatif olarak geliştirilen çeşitli çalışma tasarımları da aşı etkililiğini belirlemek için kullanılabilir. İlgili aşı ve hastalığa ve mevcut olanaklara göre kohort ve olgu kontrol çalışmalarının yanı sıra indirekt kohort yöntemi, test negatif olgu kontrol tasarımı, olgu olgu çalışması, tarama yöntemi, hane halkı temas çalışması gibi alternatif tasarımlardan uygun olan kullanılarak aşı etkililiği belirlenebilir. Bu tasarımlardan başka olgu kohort çalışması, iç içe olgu-kontrol çalışması, insidans yoğunluğu olgu kontrol tasarımı gibi farklı alanlarda kullanılmakta olan tasarımlar da aşı etkililiğini belirlemek için seçilebilecek tasarımlar arasındadır. Ancak bu tasarımların hiç birinin mükemmel olmadığı ve çeşitli genel varsayımların yanı sıra tasarıma göre farklı varsayımlar altında yürütülmeleri gerektiği unutulmamalıdır. getirilmediği ölçüde aşı etkililiği tahmini gerçek değerinden uzaklaşır. Aşılı veya aşısız gruptaki atak Gerekli varsayımların yerine hızını olduğundan daha az veya daha fazla gösteren herhangi bir faktör aşı etkililiği tahmininde taraf tutmaya yol açar. Bu faktörlerin tasarım aşamasında veya analiz sırasında mümkün olduğunca kontrol edilmesi gerekir. Aşı etkililiği tahminlerinin yanıltıcı olmaması için uygun tasarımın seçilmesi ve seçilen tasarıma göre gereken varsayımlar, olası taraf tutma kaynakları ve karıştırıcılar çalışmanın planlama aşamasında ve çalışma sonuçları yorumlanırken mutlaka göz önünde bulundurulmalıdır

Anahtar Kelimeler

• Aşı etkililiği, aşı epidemiyolojisi, çalışma tasarımları

Vaccine epidemiology: epidemiologic study designs for vaccine effectiveness

Öz

Protection level against a disease of interest by application of a licenced vaccine whose effectiveness has been proved in a population is measured by “vaccine effectiveness” which is determined with observational epidemiological studies conducted under non-ideal field conditions. For determination of whether decrease in incidence of related disease in a population is due to vaccination or other reasons rather than vaccination, vaccine effectiveness should be monitored as a routine part of the surveillance. Therefore, vaccine effectiveness studies play an important role in public health actions. Various other study designs that are developed as an alternative to classical observational epidemiological studies such as cohort and case-control studies can also be used in determination of vaccine effectiveness. In accordance with related vaccine and disease and current facilities, vaccine effectiveness can be determined by using appropriate one of the alternative designs such as indirect cohort method, test-negative case-control design, case-case study, the screening method, household contact study, as well as cohort and case-control studies. Additionally, study designs which are used in other fields such as case-cohort study, nested case-control study, incidence density case-control design are among the designs that can be chosen for determination of vaccine effectiveness. However, it should be remembered that none of them is perfect and they should be performed under different assumptions related with each design, as well as various general assumptions. How necessary assumptions are not fulfilled, estimation of vaccine effectiveness will go far from its actual value. Any

Anahtar Kelimeler

• Vaccine effectiveness, vaccine epidemiology, study designs

Kaynakça

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