Approximately 50%–70% of women develop serum antibodies after naturally acquired infection with HPV-16 or HPV-18. Naturally acquired antibodies can remain detectable for at least 4–5 years, albeit at much lower levels than those induced by vaccination. Whereas some studies have not shown an immune protection role for naturally acquired antibodies, others have shown that they may provide protection against future infection. Underpowering of studies and differences in methodology may explain these discrepancies. In addition, the levels of naturally acquired antibodies that may provide protection have not yet been established.
Vaccine efficacy data from the Papilloma Trial Against Cancer in Young Adults (PATRICIA) of the HPV-16/18 AS04-adjuvanted vaccine (Cervarix) have been reported previously. The intensive follow-up of the control arm of large vaccine trials provides an opportunity to evaluate the natural history of HPV infection, including the impact of naturally induced antibodies on infection and cervical abnormalities. The present paper describes an analysis of the risk of newly detected HPV infection and development of cervical abnormalities according to the baseline level of naturally acquired antibodies to HPV-16 or HPV-18 in women from the control group of PATRICIA over a 4-year follow-up.
Naturally acquired antibodies to HPV-16, and to a lesser extent HPV-18, are associated with some reduced risk of subsequent infection and cervical abnormalities associated with the same HPV type.