Table 2 Efficacy of prophylaxis: cases of VKDB grouped by VK actually received, from the three surveys of incidence (1988–2002).

Prophylaxis received	Estimated* at‐risk population†	Cases of VKDB	Estimated* incidence	Relative risk versus IM‡ (95% CI)
Intramuscular	2535 000	3§	1 in 845 000	1
Oral beyond a week	928 000	4¶	1 in 232 000	3.64 (0.82 to 16.3), p = 0.07
Oral not beyond a week	861 000	25¶	1 in 34 000	24.53 (7.4 to 81), p = <0.001
Nil	290 000	34	1 in 8 500	99 (29 to 402), p = <0.001

*Estimated because firm data were unavailable as some babies are given different prophylaxis from that routinely recommended for normal risk deliveries, either through parental choice or clinician allocation.

†Population includes all infants (all gestations, birth weights, risk categories, etc).

‡Calculation of RR shows little variation between the three studies.

§One received only 100 μg VK.

¶In the 2001–02 study, two infants bled after receiving oral VK; one probably had multiple doses beyond day 7, the other two doses in the first week.