Table 1. Relative risk of cervical cancer [95% confidence interval] after two or more negative screenings over time since the last negative screening for women aged 35–64 years and the number of actual cancer cases (1994–1997).

	Relative risk
Interval	Incidence in 1965–1969	Projected incidencea in 1994–1997 in a situation without screening	Number of cancer cases
0–6 months	0.12 [0.08–0.17]	0.26 [0.18–0.39]	26
7–12 months	0.06 [0.03–0.10]	0.14 [0.08–0.23]	13
1–2 years	0.08 [0.06–0.12]	0.19 [0.13–0.26]	31
2–4 years	0.15 [0.11–0.19]	0.33 [0.26–0.42]	65
4–6 years	0.20 [0.14–0.29]	0.45 [0.32–0.64]	31
6–10 years	0.18 [0.11–0.30]	0.41 [0.25–0.68]	15

Two different ways of calculating the background incidence (i.e. the denominator of the relative risk) were used (see text).

^aBased on the APC analysis of prescreening mortality (see Discussion).