Estimating the number needed to vaccinate to prevent diseases and death related to human papillomavirus infection.
BACKGROUND
A vaccine against human papillomavirus (HPV) types 6, 11, 16 and 18 is now licensed for use in Canada and many other countries. We sought to estimate the number needed to vaccinate to prevent HPV-related diseases and death.


METHODS
A cohort model of the natural history of HPV infection was developed. Model simulations were based on 209 different parameter sets that reproduced Canadian HPV type-specific data for infection, cervical intraepithelial neoplasia, cervical cancer and genital warts. The number needed to vaccinate was calculated as the number of women who would need to be vaccinated to prevent an HPV-related event during their lifetime.


RESULTS
Among 12-year-old girls, we estimated that the number needed to vaccinate to prevent an episode of genital warts would be 8 (80% credibility interval [CrI] 5-15) and a case of cervical cancer 324 (80% CrI 195-757). These estimates were based on the assumption that the vaccine procures lifelong protection and that its efficacy is 95%. If vaccine protection is assumed to wane at 3% per year, the predicted number needed to vaccinate would increase to 14 (80% CrI 6-18) and 9080 (80% CrI 1040-does not prevent), respectively. The latter number would be greatly reduced with the addition of a booster dose, to 480 (80% CrI 254-1572).


CONCLUSIONS
Our model predictions suggest that vaccination with the currently available HPV vaccine may significantly reduce the incidence of genital warts, cervical intraepithelial neoplasia and cervical cancer. However, the benefits (particularly in terms of cervical cancer reduction) are highly dependent on the duration of vaccine protection, on which evidence is currently limited.
Brisson
Marc
M
Département de médecine sociale et préventive, Université Laval, Québec, Que. marc.brisson@uresp.ulaval.ca
Van de Velde
Nicolas
N
De Wals
Philippe
P
Boily
Marie-Claude
MC
D002170:Canada / Q000453:epidemiology; D002648:Child; D015331:Cohort Studies; D003198:Computer Simulation; D003218:Condylomata Acuminata / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology*; D005260:Female; D006801:Humans; D008962:Models, Theoretical; D030361:Papillomavirus Infections / Q000453:epidemiology / Q000517:prevention & control*; D053918:Papillomavirus Vaccines / Q000008:administration & dosage*; D018401:Sample Size; D035501:Uncertainty; D002583:Uterine Cervical Neoplasms / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology*; D002578:Uterine Cervical Dysplasia / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology*
D053918:Papillomavirus Vaccines
Vaccine. 2002 Jan 15;20(7-8):1113-25
11803072
Sex Transm Infect. 2000 Jun;76(3):162-8
10961190
N Engl J Med. 2003 Feb 6;348(6):518-27
12571259
Clin Infect Dis. 2003 Jun 1;36(11):1397-403
12766834
Br J Cancer. 2003 Jul 7;89(1):101-5
12838308
J Natl Cancer Inst. 2004 Apr 21;96(8):604-15
15100338
Vaccine. 2004 Jun 2;22(17-18):2192-8
15149776
Virology. 2004 Jun 20;324(1):17-27
15183049
J Clin Microbiol. 1995 Aug;33(8):2058-63
7559948
Emerg Infect Dis. 2004 Nov;10(11):1915-23
15550200
J Infect Dis. 2005 Mar 1;191(5):731-8
15688287
Lancet Oncol. 2005 May;6(5):271-8
15863374
Lancet. 2006 Apr 15;367(9518):1247-55
16631880
Br J Cancer. 2006 Dec 4;95(11):1459-66
17117182
Br J Cancer. 2007 Jan 15;96(1):143-50
17146475
Br J Cancer. 2007 Feb 12;96(3):514-8
17245341
Am J Epidemiol. 2007 Apr 1;165(7):762-75
17276976
Emerg Infect Dis. 2007 Jan;13(1):28-41
17370513
Vaccine. 2007 May 22;25(21):4324-33
17445955
N Engl J Med. 2007 May 10;356(19):1915-27
17494925
N Engl J Med. 2007 May 10;356(19):1928-43
17494926
N Engl J Med. 2007 May 10;356(19):1991-3
17494933
Vaccine. 2007 Jun 21;25(26):4931-9
17499406
Vaccine. 2007 Jul 20;25(29):5433-40
17560695
Clin Microbiol Rev. 2003 Jan;16(1):1-17
12525422