Table 1. Estimating maternal vaccination coverage by ANC visit.

ANC visit	Women eligible for vaccination	Eligible women who visited ANC in a given window	Eligible women who received vaccination	Women ineligible to receive vaccine at next visit
ANC1	All pregnant women	% pregnant women attending ANC1 during vaccination window * A * % ANC1 coverage	B * Service availability and acceptance proxy	Women who reached 40 weeks’ gestation or greater by the subsequent visit + C
	= [A]	= [B]	= [C]	= [D]
ANC2	Number of pregnant women eligible for ANC2, i.e., (A–D)	E * % ANC2 coverage	F * Service availability and acceptance proxy	Women who reached 40 weeks’ gestation or greater by the subsequent visit + G
	= [E]	= [F]	= [G]	= [H]
ANC3	Number of pregnant women eligible for ANC3, i.e., (E–H)	I * % ANC3 coverage	J * Service availability and acceptance proxy	Women who reached 40 weeks’ gestation or greater by the subsequent visit + K
	= [I]	= [J]	= [K]	= [L]
ANC4	Number of pregnant women eligible for ANC3, i.e., (I–L)	M * % ANC4 coverage	N * Service availability and acceptance proxy	Women who reached 40 weeks’ gestation or greater by the subsequent visit + O
	= [M]	= [N]	= [O]	= [P]

$\mathit{A}\mathit{N}\mathit{C}\mathit{a}\mathit{t}\mathit{t}\mathit{e}\mathit{n}\mathit{d}\mathit{a}\mathit{n}\mathit{c}\mathit{e}\mathit{i}\mathit{n}\mathit{a}\mathit{g}\mathit{i}\mathit{v}\mathit{e}\mathit{n}\mathit{w}\mathit{i}\mathit{n}\mathit{d}\mathit{o}\mathit{w}=\frac{\left[B\right]+\left[F\right]+\left[J\right]+\left[N\right]}{\left[A\right]}$

$\mathit{O}\mathit{v}\mathit{e}\mathit{r}\mathit{a}\mathit{l}\mathit{l}\mathit{m}\mathit{a}\mathit{t}\mathit{e}\mathit{r}\mathit{n}\mathit{a}\mathit{l}\mathit{v}\mathit{a}\mathit{c}\mathit{c}\mathit{i}\mathit{n}\mathit{a}\mathit{t}\mathit{i}\mathit{o}\mathit{n}\mathit{c}\mathit{o}\mathit{v}\mathit{e}\mathit{r}\mathit{a}\mathit{g}\mathit{e}=\frac{\left[C\right]+\left[G\right]+\left[K\right]+\left[O\right]}{\left[A\right]}$

"ANC attendance in a given window” counts women more than once if their ANC visit occurs multiple times within the window.