ab‐Bloom 1975.

Study characteristics
Methods	RCT, double‐blind
Participants	282 children (11 months to 4 years old) absence of any history of natural measles mumps and rubella or immunisation against these diseases. Absence of any usual medical contraindication.
Interventions	3 lots of MMR vaccine (lot 1, 2, 3 prepared from Schwarz live attenuated measles virus, Jeryl Lynn live attenuated measles virus, and Cenedehill live attenuated measles virus) versus placebo. Vaccines contained at least 1000 TCID50 for measles and rubella and 5000 for mumps.
Outcomes	Observations for intercurrent illness and vaccine reactions made approximately 3 times/child between 7 to 21 days postvaccination: Temperature elevation above normal 1.5 °F Rash Lymphadenopathy Coryza Rhinitis Cough Other Local reaction Limb and joint symptoms
Funding Source	Mixed (government and pharmaceutical industry)
Notes	The study does not say if all children were observed at least once.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Unclear
Allocation concealment (selection bias)	Unclear risk	Unknown, but decoding and tabulation done by computer
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	High risk	16% of possible total observations missing
Selective reporting (reporting bias)	High risk	No explanation for excluding symptom reports
Summary Risk of Bias assessment	High risk	We had concerns regarding multiple domains such that our confidence in the result is substantially lowered.