About this Session

In this session you will learn about causal impact, the fundamental challenge of causal inference, and threats to internal validity. We will also introduce you to several research designs for estimating causal impact that will become our focus later this semester.

Preparing for Class

  • GHR Chapter 5
  • Krauer, F., Riesen, M., Reveiz, L., Oladapo, O. T., Martinez-Vega, R., Porgo, T. V., … & WHO Zika Causality Working Group. (2017). Zika Virus Infection as a Cause of Congenital Brain Abnormalities and Guillain–Barré Syndrome: Systematic Review. PLoS Medicine, 14(1), e1002203.
  • de Araújo, T. V. B., Rodrigues, L. C., de Alencar Ximenes, R. A., de Barros Miranda-Filho, D., Montarroyos, U. R., de Melo, A. P. L., … & Cordeiro, M. T. (2016). Association between Zika virus infection and microcephaly in Brazil, January to May, 2016: preliminary report of a case-control study. The Lancet Infectious Diseases, 16(12), 1356-1363.
  • Brasil, P., Pereira, Jr, J. P., Raja Gabaglia, C., Damasceno, L., Wakimoto, M., Ribeiro Nogueira, R. M., … & Calvet, G. A. (2016). Zika virus infection in pregnant women in Rio de Janeiro—preliminary report. New England Journal of Medicine, 375, 2321-2334.
  • Review the application activity that we will complete in class
  • Pre-class readiness assessment


Posted here after class

In-Class Activity

In October 2015, Brazil reported an unusual increase in the number of cases of microcephaly among newborns. This announcement came several months after reports of Zika virus circulating in the country. Physicians and public health officials worried about a possible link between Zika and microcephaly. Before the end of the year, the WHO organized a 5-day mission to Brazil for experts to review available data, inform the design of new studies, and assess laboratory capacity. A systematic review of the evidence followed, and on September 7, 2016, a WHO expert panel concluded:

The most likely explanation of available evidence from outbreaks of Zika virus infection and clusters of microcephaly is that Zika virus infection during pregnancy is a cause of congenital brain abnormalities including microcephaly.

In this activity you will examine how the expert panel came to this conclusion as an example of causal inference in epidemiology. You will also consider why evidence from certain types of studies are generated more quickly than others.

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