Non-specific effects of vaccination

doi:10.1136/bmj.330.7495.844-b

From trainee to consultant, BMJ Group offers doctors around the world tailored information, special events, learning resources and recruitment services at every step along their career path.

... by doctors, for doctors, for patients
We are open for entries!

Online learning

BMJ Learning

High-quality CME / CPD for doctors and other healthcare professionals. BMJ Learning features hundreds of accredited, peer-reviewed learning modules in text, video, and audio formats. Find out more

Courses and Qualifications

BMJ Masterclasses

BMJ Masterclasses, led by experts, help clinicians to use the latest evidence and recent guidelines in practice and meet their CPD/CME requirements. Find out more

Exam Preparation

The leading provider of online exam preparation, helping over 167,000 healthcare professionals to pass their exams. Find out more

onExamination

Search all BMJ comment articles:

From

Limit by

Access to the full text of this article requires a subscription or payment. Please log in or subscribe below.

Survival bias may explain findings

Peter Aaby, professor (psb@mail.gtelecom.gw),
Henrik Jensen, senior statistician,
Christine Stabell Benn, senior researcher,
Ida Maria Lisse, registrar

Bandim Health Project, Danish Epidemiology Science Centre, Statens Serum Institute, Apartado 861, Bissau, Guinea-Bissau

EDITOR—Vaugelade et al found the BCG and diphtheria-tetanus and pertussis vaccines (DTP) to be associated with reductions in mortality greater than expected from disease prevention.1 However, as they admit, dead vaccinated children may have been misclassified because their vaccination cards were destroyed.

In a survival analysis using vaccination dates as time dependent covariates, surviving children change status at date of vaccination even though vaccinations …