Grand Rounds

HPV Vaccines: Cochrane Reviews Looks at the Evidence with Multi-Year Follow-Up

BACKGROUND AND PURPOSE:

While HPV is common and usually cleared by the immune system, high-risk (hrHPV) types can lead to precancerous lesions
Arbyn et al. (Cochrane Reviews, 2018) assessed the efficacy HPV vaccines in protecting against cervical precancer and HPV16/18 infection in adolescent girls and women

Database search of RCTs comparing efficacy and safety
Participants: Females offered HPV vaccines vs placebo
Primary outcomes
- Precancer associated with vaccine HPV types
- Precancer irrespective of HPV type
Cervical precancer
- CIN grade 2 and above (CIN2+)
- CIN grade 3 and above (CIN3+)
- AIS

26 trials were included, totaling 73,428 participants
10 trials, with follow-up of 1.3 to 8 years, addressed protection against CIN/AIS
Vaccine safety was assessed over a 6-month to 7-year period in 23 studies
hrHPV negative at baseline: HPV vaccines reduced CIN2+, CIN3+, AIS associated with HPV16/18 compared with placebo
- CIN2+: 164 to 2/10,000; Risk Ratio [RR] 0.01; 95% CI, 0 to 0.05 (high certainty evidence)
- CIN3+: 70 to 0/10,000; RR 0.01; 95% CI, 0.00 to 0.10 (high certainty evidence)
- AIS: 9 to 0/10,000; RR 0.10; 95% CI, 0.01 to 0.82 (moderate certainty evidence)
HPV16/18 negative at baseline:
- Vaccines also reduced CIN2+, CIN3+, AIS associated with HPV16/18 (high to moderate certainty evidence)
Regardless of HPV status at baseline: Vaccines had a similar impact, reducing risk CIN2+, CIN3+, AIS associated with HPV16/18 (high to moderate certainty evidence)
There was no difference in adverse events or deaths in women exposed to HPV vaccines, compared to control
There was no increased risk for
- Miscarriage: RR 0.88; 95% CI, 0.68 to 1.14 (high certainty evidence)
- Elective termination/induced abortion RR 0.90; 95% CI, 0.80 to 1.02 (high certainty evidence)
Congenital abnormalities and stillbirths: Uncertain as to whether there is an association (wide CIs, overlapping 1)
- Effects similar between vaccine and non-vaccine group, but cannot rule out association based on the current review due to study design/sample size

Studies were not of sufficient duration nor size to make conclusions of risk for cervical cancer
There is high-certainty evidence that HPV vaccines protect against cervical precancer, with the effect highest for lesions associated with HPV16/18
Effect is higher for those who are negative for hrHPV or HPV16/18 at baseline compared to unselected HPV status, but effect still present in all cohorts
Any deaths that occurred were not associated with the vaccine
Long-term effects of the vaccine need to continue to be monitored

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