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TOPLINE:

One or two human papillomavirus (HPV) vaccine doses effectively prevent high-grade cervical lesions in girls aged 10-16 years, offering similar protection as three doses. Vaccination before the age of 15 years provides optimal protection and supports World Health Organization's (WHO's) recommendation.

METHODOLOGY:

• The researchers aimed to evaluate the effectiveness of the quadrivalent HPV vaccine against high-grade cervical lesions, considering both the age at vaccination and the number of doses received.
• The study included 2,200,495 Swedish girls or women aged 10-35 years between 2006 and 2022, of whom 584,676 received at least one dose of the vaccine.
• Data were collected from Swedish national registries, with follow-up durations ranging from 4 to 16 years.
• Participants received either no, one, two, or three vaccination doses and were categorised into age groups of 10-14, 15-16, 17-20, and 21-35 years.
• The primary outcome was the first diagnosis of high-grade cervical lesions.

TAKEAWAY:

• Vaccinated individuals had a significant lower risk for high-grade cervical lesions than unvaccinated individuals, with an overall incidence rate ratio (IRR) of 0.62.
• Vaccination with one to three doses yielded comparable protection before the age of 15 years, with an IRR of 0.42 for one dose, 0.54 for two doses, and 0.50 for three doses.
• Among individuals aged 15-16 years, the IRR was 0.60 for one dose, 0.55 for two doses, and 0.54 for three doses, whereas for those aged 17-20 years, the IRR was 0.73 for one dose, 0.72 for two doses, and 0.64 for three doses, indicating stronger protection in younger age groups.
• The overall IRRs for one, two, and three vaccine doses were 0.73, 0.70, and 0.59, respectively, indicating greater effectiveness as the number of doses increased.

IN PRACTICE:

"Receiving one or two doses of HPV vaccines prior to age 17, especially for those initiating before age 15, has demonstrated comparable effectiveness with those who received three doses, which supports WHO's current recommendation of using a one-dose HPV vaccine regimen in adolescents," the authors wrote.

SOURCE:

The study was led by Shiqiang Wu, Karolinska Institutet, Stockholm, Sweden, and was published online on January 5, 2025, in The Lancet Regional Health - Europe.

LIMITATIONS:

The study limitations included potential misclassification of vaccination status, the impact of a concomitant vaccination campaign, and the possibility of increased engagement in screening among vaccinated women. 

DISCLOSURES:

The study received funds from the Swedish Research Council, Swedish Research Council for Health, Working Life and Welfare, and Karolinska Institutet. The authors declared that they had no competing interests.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.