Human papillomavirus infection and reinfection in adult women: the role of sexual activity and natural immunity.

There is a paucity of data on whether or not women can be reinfected with human papillomavirus (HPV) types to which they were exposed to earlier in life and on the role of natural immunity. The observation of HPV infection at older ages may be explained by the reactivation of a latent infection or new exposure from sexual activity. Our objective was to analyze the association between reinfection and sexual activity. We analyzed data from 2,462 women enrolled in the Ludwig-McGill cohort and followed every 4 to 6 months for up to 10 years. We performed HPV typing and viral load measurements via PCR and determined HPV-16 seroreactivity at enrollment. Incidence of infection and reinfection were estimated for individual types. Adjusted relative risks (RR) for the association between infection/reinfection and new sexual partners were calculated using Cox regression. Rates of initial infection and reinfection postclearance were statistically comparable. RRs of initial infection or reinfection were consistently associated with new sexual partners [2.4 (95% confidence intervals; 95% CI, 2.0-3.1) for first infection, 3.7 (1.1-13.8) for reinfection with the same type, and 2.3 (1.5-3.7) for reinfection with a different type]. Reinfection in older women was also associated with new sexual partners (RR, 2.8; 95% CI, 1.4-5.3) as were new infections with HPV-16 among women with serologic evidence of prior HPV-16 exposure (RR, 3.0; 95% CI, 1.6-5.3). Viral loads at initial infection and at reinfection were comparable. HPV infection and reinfection were strongly associated with sexual activity. This study suggests that natural immunity does not play a role in controlling the extent of reinfections.

Type-specific duration of human papillomavirus infection: implications for human papillomavirus screening and vaccination.

BACKGROUND: Understanding the duration of human papillomavirus (HPV) infection may help find suitable end points for vaccine trials and testing intervals in screening studies. We studied genotype-specific infection duration among 2462 women enrolled in the Ludwig-McGill cohort study. METHODS: Cervical specimens collected every 4-6 months were tested by a polymerase chain reaction protocol. Actuarial techniques were used to estimate the duration of HPV infection and to investigate the influence of age, number of sexual partners, and coinfection with multiple HPV types. RESULTS: At enrollment, the prevalence of infection with high-risk HPV types was 10.6%, and the prevalence of infection with low-risk HPV types was 6.1%; incidence rates were 6.1 and 5.0 infections per 1000 women-months, respectively. Prevalent infections took longer to clear than incident infections (mean time to clearance, 18.6 months vs. 13.5 months). The mean duration of incident infection with high- and low-risk HPV varied according to the analytic approach used to measure this variable and showed considerable variation by HPV type (range, 5.1-15.4 months). Age and number of partners did not influence infection duration, whereas coinfection was associated with increased infection duration. The mean duration of HPV-16 monoinfection was 11.0 months, and the mean duration of HPV-16 coinfection was 15.4 months. CONCLUSION: There was considerable variation among HPV types with regard to the duration of infection. Coinfection with multiple types contributed to an increased infection duration.