The estimated impact of natural immunity on the effectiveness of human papillomavirus vaccination.
BACKGROUND
Mathematical modelling is used to estimate the effectiveness of HPV vaccination. These estimates depend strongly on herd immunity and thus on naturally acquired immunity, a mechanism of which little is known. We estimated the impact of different vaccination strategies on HPV-16 and HPV-18 transmission and cervical cancer incidence in the Netherlands, considering different acquired immunity mechanisms.


METHODS
We used the STDSIM microsimulation model, and considered two mechanisms for acquired immunity after infection: (I) full immunity with variable duration; (II) cumulatively decreasing susceptibility to reinfection. Girls aged 13-16 years received vaccination (94.7% efficacy for HPV-16 and 92.3% for HPV-18) during a once-off catch-up campaign with 50% coverage, followed by annual vaccination of 12-year-old girls (60% coverage). Alternative vaccination scenarios included increased coverage, including boys, and lower vaccine efficacy.


RESULTS
HPV-16 incidence reduced by 64% under mechanism I and 75% under mechanism II; HPV-18 incidence reduced by 58% and 73%, respectively, and these reductions lead to 48-56% fewer cervical cancer cases. Increasing coverage can lead to over 96% reduction in HPV incidence. Vaccinating boys reduced incidence by 79-89% for HPV-16 and 83-98% for HPV-18 in women.


CONCLUSIONS
Effectiveness estimates of HPV vaccination differ slightly between different acquired immunity mechanisms, yet these differences are unlikely to affect policy decisions. Offering vaccination to boys as well may be considered to further reduce cancer incidence.
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands. Electronic address: s.matthijsse@erasmusmc.nl.
Suzette M
SM
Matthijsse
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Jan A C
JAC
Hontelez
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Steffie K
SK
Naber
Department of Biostatistics, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Joost
J
van Rosmalen
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Kirsten
K
Rozemeijer
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Corine
C
Penning
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Roel
R
Bakker
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Marjolein
M
van Ballegooijen
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Inge M C M
IMCM
de Kok
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands.
Sake J
SJ
de Vlas
D000293:Adolescent; D000328:Adult; D052685:Alphapapillomavirus / Q000276:immunology*; D005260:Female; D049674:History, 21st Century; D052162:Human papillomavirus 16 / Q000276:immunology; D052161:Human papillomavirus 18 / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D009426:Netherlands / Q000453:epidemiology; D030361:Papillomavirus Infections / Q000150:complications / Q000453:epidemiology / Q000266:history / Q000276:immunology* / Q000517:prevention & control* / Q000635:transmission; D053918:Papillomavirus Vaccines / Q000276:immunology*; D002583:Uterine Cervical Neoplasms / Q000453:epidemiology / Q000209:etiology; D055815:Young Adult
D053918:Papillomavirus Vaccines
Cervical cancer; Human papillomavirus; Microsimulation; Modelling; Naturally acquired immunity; Vaccination