From: The quadrivalent HPV vaccine is protective against genital warts: a meta-analysis
First author (year) | Risk of selection bias: changes in the study population characteristics between the pre- and post-vaccination periods | Risk of information bias: errors in the identification of HPV+ during the pre- and post-vaccination period (data source, genital wart case definition, outcome used) | Risk of confounding: changes in HPV infection between the pre- and post-vaccination periods could be diluted/exacerbated by other variables |
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Dominiak-Felden (2015) [17] | High Some people possibly may have been vaccinated without reimbursement (risk of misclassification), imiquimod agreement was used as the date of vaccination. | High A surrogate marker (imiquimod agreement) was used as definition of genital wart cases (risk of underestimation). | High Different sexual behaviours between vaccinated and unvaccinated women. |
Chow (2015) [28] | High Possible changes in the clientele of the sexual health services between the periods. Self-reported vaccination status and the number of doses of HPV vaccine. | Low Clinical diagnosis by clinicians. | High Clients at sexual health service have higher risk of sexually transmissible infections. |
Ali (2013) [27] | High Possible changes in the clientele of the sexual health services between the periods. Self-reported vaccination status and the number of doses of HPV vaccine. | Low Genital warts are directly diagnosed by physicians. | High Changes in sexual activity, health seeking behaviour could potentially cause changes in genital wart frequency over time. |
Harrison (2014) [29] | Unclear Some women from the vaccination eligible group may be included with non-vaccine eligible women due to the change in patient age. | Low Genital wart diagnosis by physicians. | High Change in sexual risk behaviour. |
Read (2011) [31] | Unclear Possible changes in the clientele of the Melbourne Sexual Health Centre. | Low Genital wart diagnosis by physicians. | Unclear Possible HPV infection of 21–29 years women before the vaccination. |
Fairley (2009) [30] | Unclear Possible changes in the clientele of the Melbourne Sexual Health Centre. | Low Genital wart diagnosis by physicians. | Unclear Boys aged 9–15 years could be prescribed the vaccine privately. |
Checchi (2019) [32] | Unclear Inability to link anogenital wart diagnoses to individual vaccination status. | Low Genital wart diagnosis by physicians. | Unclear Patients could attend elsewhere for treatment of anogenital wart. |
Mann (2019) [33] | Unclear Patients’ vaccination status is unknown. | Low Genital wart diagnosis by physicians. | Unclear Patients with anogenital wart could choose to seek care elsewhere. |