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EFFECT OF HPV VACCINE ON PREEXISTING HPV INFECTION

is compared with the control group, was defined as

(Pr [viral persistence in control group]−Pr [viral persistence in HPV vaccine group])/Pr (viral persistence in control group)=

1−(Pr [viral persistence in HPV vac- cine group]/Pr [viral persistence in con- trol group])=

1 − RR, where Pr represents the probability of persistence at the time point of in- terest (6 or 12 months) and RR is the ratio of the probability (risk) of persis- tence in the 2 groups. Ninety-five per- cent confidence intervals (CIs) around VEVC estimates were computed from the CIs for the RR.

The generalized estimating equa- tions method was used to account for possible lack of independence between clearance in analysis of more than 1 in- fection in the same woman.26 The esti- mates of the proportion of infections that clear from the generalized estimating equations analysis can, therefore, be slightly different from the crude percent- ages. We present VEVC against persis- tence for several HPV categories at the 6-month and 12-month visits overall as well as restricted to women who re- ceived all vaccine doses and to those with evidence of a single HPV type at entry. Additional analyses were performed to evaluate VEVC stratified by the follow- ing entry parameters of interest: HPV- 16/18 antibodies (positive for either vs negative for both), cytologic findings (normal vs atypical squamous cells of un- certain significance), HC2 viral load (relative light unit values, 0-2.0, 2.0-

  • 50, and 50), months since sexual de-

but (0-36 months, 37-72 months, and

  • 73 months), oral or injectable contra-

ceptive use (current users vs not cur- rent users), cigarette smoking (current smokers vs not current smokers), and chlamydia/gonorrhea findings (posi- tive for either vs negative for both).

RESULTS Study Population

A total of 7466 women were enrolled and randomized (FIGURE). For the pre- sent evaluation, we excluded 4 women

who inadvertently received both vac- cine types. Among the remaining 7462 women, 3726 were randomized to the

HPV vaccine group and 3736 to the control group. A total of 1594 women (775 in the HPV vaccine group and 819

Figure. Participant Flow

24 467 Screened

17 001 Excluded 3561 Ineligible (out of area) 2186 Ineligible (other reasons) 1527 Not located 5158 Refused 4569 In deferred status at end of enrollment

7466 Women randomized

3727 Randomized to receive HPV-16/18 vaccine 3726 Received vaccine as assigned 1 Received discordant vaccines

3739 Randomized to receive control vaccine 3736 Received vaccine as assigned 3 Received discordant vaccines

2533 Excluded 1 Received discordant vaccines 772 Not sexually active 3 No pelvic examination

60 Had evidence of high-grade squamous intraepithelial lesions or more severe disease and referred to colposcopy

1471 HPV negative 226 HPV positive for unknown type

2557 Excluded 3 Received discordant vaccines

819 Not sexually active 50 Had evidence of high-grade squamous intraepithelial lesions or more severe disease and referred to colposcopy

1456 HPV negative 229 HPV positive for unknown type

1194 HPV positive for known type

1182 HPV positive for known type

162 Did not have 6-mo HPV test resultsa

159 Did not have 6-mo HPV test resultsa

147 Missed visits

138 Missed visits

14 Discontinued study

19 Discontinued study

1 PCR test results not yet available

2 PCR test results not yet available

1032 Included in 6-mo HPV PCR-based analyses (1730 infections)b

1023 Included in 6-mo HPV PCR-based analyses (1737 infections)b

369 Did not have 12-mo HPV test results

336 Did not have 12-mo HPV test results

234 Missed visits

222 Missed visits

34 Discontinued study

31 Discontinued study

49 PCR test results not yet available

38 PCR test results not yet available

52 12-mo study visit not yet conducted

45 12-mo study visit not yet conducted

825 Included in 12-mo HPV PCR–based analyses (1329 infections)c

846 Included in 12-mo HPV PCR–based analyses (1389 infections)c

HPV indicates human papillomavirus; PCR, polymerase chain reaction. a Results not available at the time of data freeze (data freeze dates: March 29, 2007, for clinical database; June

26, 2006, for risk factor questionnaire database; April 25, 2007, for HPV PCR database; and July 17, 2006, for

HPV-16/18 serology database). bAnalysis of clearance of Hybrid Capture 2–positive infections detected at entry were based on 666 women in the

HPV vaccine group and 663 women in the control group, as described in the “Methods” section of the text. cIncludes 134 women (56 in the HPV vaccine group and 78 in the control group) who did not have HPV PCR

results available from the 6-month visit.

©2007 American Medical Association. All rights reserved.

(Reprinted) JAMA, August 15, 2007—Vol 298, No. 7

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