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Investigators from multiple institutions conducted a prospective study to evaluate type-specific antibody kinetics and stability for 24 months after a single dose of nonavalent human papillomavirus (HPV) vaccine in children. Study participants were healthy children 9–11 years old at baseline, recruited from pediatric clinics affiliated with the University of Arizona, Tucson, AZ, and University of California at Los Angeles. At baseline, study children were administered a dose of HPV vaccine. A second dose was administered 24 months later. Blood was obtained from participants for HPV type-specific antibodies (HPV16 and HPV18) at baseline, 6, 12, 18, 24, and 30 months. The stability of the antibody response in study children was compared between each time point, with the primary study outcome being the stability of HPV16 and HPV18 antibody levels between months 12 and 18 and months 18 and 24. Antibody levels were considered stable if there was less than a 2-fold change in levels between the 2 time points, increased if there was a ≥2-fold increase, and decreased if there was a ≥2-fold decrease.
Data were analyzed on 201 participants, including 143 girls and 58 boys. A total of 187 children (93%) completed the 30-month visit. At enrollment, the mean age of study participants was 10.8 ±0.8 years; 49.8% were of Hispanic/Latino ethnicity. At baseline, antibody levels to HPV16 and HPV18 were below the assay cutoff value in 96% and 80% of participants, respectively. HPV16 geometric mean concentrations (GMCs) rose to 25.20 IU/mL at 6 months, decreased to 14.54 IU/mL at 12 months, and remained stable at months 18 and 24 (15.01 and 15.05 IU/mL, respectively). A similar pattern was seen with HPV antibody levels, with GMCs of 10.67, 7.27, 7.23, and 7.11 IU/mL at months 6, 12, 18, and 24, respectively. After the booster dose at 24 months, antibody levels rose markedly, with GMCs of 427.1 IU/mL to HPV16 and 134.8 IU/mL to HPV18. Using the a priori definitions for stable, increased, and decreased, 38.6% and 24.0% of study children had decreases in antibody levels to HPV16 and HPV18 between months 6 and 12. The majority of children had stable antibody levels between months 12 and 18 (90.5% for HPV16 and 91.6% for HPV18) and between months 18 and 24 (91.6% and 92.2%, respectively).
The authors conclude that a single dose of nonavalent HPV vaccine led to persistent and stable antibody levels to HPV16 and HPV18 for up to 24 months.
Dr Raphael has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.
In 2021, the worldwide HPV vaccine coverage rate in girls was 21%.1 Elimination of the need for repeat doses has substantial potential to improve implementation of global HPV vaccine programs.
The current...
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