ca‐Hales 2016.

Study characteristics
Methods	Cohort study: secondary attack rate study to evaluate measles vaccine effectiveness in household contacts
Participants	Households were selected for the study by convenience sampling of confirmed measles cases reported to the Pohnpei State Department of Health Services, with laboratory‐confirmed cases prioritised. Was excluded the following from analysis: 1) Co‐primary cases 2) Household contacts aged < 6 months (maternal antibodies may confer protection in these infants) 3) Household contacts aged ≥ 40 years (vaccination records were rarely available for this age group) 4) Individuals with incomplete vaccination records
Interventions	1) Vaccinations administered before 1 June 2014 as pre‐campaign doses 2) Vaccinations administered on or after 1 June 2014 as campaign doses 3) Pre‐exposure campaign dose as a dose received ≥ 5 days before rash onset in the primary case 4) Postexposure campaign dose as a dose received between 4 days before to 3 days after rash onset in the primary case Vaccination status of study participants ascertained by vaccination card or vaccine registry.
Outcomes	A confirmed measles case was defined according to the US Council of State and Territorial Epidemiologists guidelines: a person with acute febrile rash illness with detection of measles‐specific nucleic acid from a clinical specimen using PCR, or a positive serologic test for measles IgM antibody, or direct epidemiologic linkage to another confirmed case. Laboratory testing was performed at the Centers for Disease Control and Prevention.
Funding Source	Government
Notes	Authors' conclusion: "Our results support implementation of a vaccination campaign as soon as possible after introduction of measles into a population with suboptimal levels of measles immunity, as evidenced by the protective effect of both pre‐exposure and postexposure campaign doses."
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS ‐ exposed cohort selection	High risk	There was insufficient information.
PCS/RCS ‐ non‐exposed cohort selection	Unclear risk	There was insufficient information.
PCS/RCS ‐ comparability	High risk	Only convenience sampling
PCS/RCS ‐ assessment of outcome	Low risk	Adequate ‐ laboratory‐confirmed
Summary Risk of Bias assessment	High risk	We had concerns regarding multiple domains such that our confidence in the result is substantially lowered.