2. Intervention‐outcome matrix.

Intervention	Vaccination coverage	Equity	Knowledge	Attitudes	Beliefs	Adverse effects	Cost	Vaccine‐preventable diseases
Recipient‐oriented interventions
1 Health education vs usual practice	✔㊉㊉㊉㊉1	NR	✔㊉㊉㊀㊀2	NR	NR	NG	NR	NR
2. Complex vs simplified health education	Ø㊉㊉㊉㊀3	NR	✔㊉㊉㊀㊀3	NR	NR	NR	NR	NR
3. Financial incentives vs usual practice	✔㊉㊉㊀㊀4	NR	NR	NR	NR	NR	NR	NR
4. Health education plus financial incentives vs usual practice	?㊉㊀㊀㊀5	NR	?㊉㊀㊀㊀5	NR	NR	NR	NR	NR
5. Mandatory vaccination vs usual practice	✔㊉㊉㊉㊀6	NR	NR	NR	NR	NR	NR	NR
Provider‐oriented interventions
6. Provider prompts vs usual practice	✔㊉㊉㊉㊀7	NR	NR	NR	NR	NR	NR	NR
7. Provider education plus performance feedback vs usual practice	✔㊉㊉㊀㊀8	NR	NR	NR	NR	NR	NG	NR
Health system interventions
8. Class‐based vs age‐based HPV vaccination in schools	✔㊉㊉㊉㊀9	NR	NR	NR	NR	NR	NG	NR
Multi‐component interventions
9. Multi‐component provider intervention vs usual practice	✔㊉㊉㊀㊀10	NR	NR	NR	NR	NR	NR	NR
10. Multi‐component provider and parent intervention vs usual practice	✔㊉㊉㊀㊀11	NR	✔㊉㊉㊀㊀12	NR	NR	NR	NR	NR

✔ = a desirable effect

Ø = little or no effect

? = uncertain effect

x = undesirable effect

vs = Compared to

NR = not reported

NG = outcome not graded

¹Diclemente 2015 (randomised trial), Grandahl 2016 (cluster‐randomised trial), and Winer 2016 (cluster‐randomised trial).

²Gargano 2015 (randomised trial).

³Skinner 2000 (randomised trial).

⁴Mantzari 2015 (randomised trial).

⁵Schwarz 2008 (randomised trial).

⁶Wilson 2005 (non‐randomised trial).

⁷Szilagyi 2015 (randomised trial).

⁸Fiks 2016 (controlled before‐after study).

⁹Watson‐Jones 2012 (cluster‐randomised trial).

¹⁰Perkins 2015 (cluster‐randomised trial).

¹¹Paskett 2016 (randomised trial) and Cates 2014 (non‐randomised trial).

¹²Paskett 2016 (randomised trial)

⊕⊕⊕⊕ = High‐certainty evidence

Definition: this research provides a very good indication of the likely effect. The likelihood that the effect will be substantially different is low.

Implications: this research provides a very good basis for making a decision about whether to implement the intervention. Impact evaluation and monitoring of the impact are unlikely to be needed if it is implemented.

⊕⊕⊕⊖ = Moderate‐certainty evidence

Definition: this research provides a good indication of the likely effect. The likelihood that the effect will be substantially different is moderate.

Implications: this evidence provides a good basis for making a decision about whether to implement the intervention. Monitoring of the impact is likely to be needed and impact evaluation may be warranted if it is implemented.

⊕⊕⊖⊖ = Low‐certainty evidence

Definition: this research provides some indication of the likely effect. However, the likelihood that it will be substantially different is high.

Implications: this evidence provides some basis for making a decision about whether to implement the intervention. Impact evaluation is likely to be warranted if it is implemented.

⊕⊖⊖⊖ = Very low certainty evidence

Definition: this research does not provide a reliable indication of the likely effect. The likelihood that the effect will be substantially different is very high.

Implications: this evidence does not provide a good basis for making a decision about whether to implement the intervention. Impact evaluation is very likely to be warranted if it is implemented.