Obaro 2004.

Methods	The study was a randomized, double‐blind, controlled trial.
Participants	Country: The Gambia. Number: 56 women in the intervention group and 57 women in the control group. Mean age: data not available. Mean gestational age: data not available.
Interventions	23‐valent pneumococcal polysaccharide vaccine vs meningococcal vaccine.
Outcomes	Pneumococcal polysaccharide‐specific s‐IgA antibody concentrations in breast milk.
Notes	Did not contribute data to analysis.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants were vaccinated with 1 dose of either a pneumococcal vaccine or control by computer‐generated random assignment.
Allocation concealment (selection bias)	Unclear risk	Details were not reported.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: “double blind”.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: “double blind”.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Two mothers withdrew their consent before the completion of the study, and 6 mothers traveled out of the study area and did not return before the completion of the study.
Selective reporting (reporting bias)	Low risk	All outcomes were predefined and reported.
Other bias	Low risk	The trial appears to be free of industry sponsorship.