Percent of women who received at least two doses of tetanus-toxoid vaccine in their last pregnancy

The proportion of pregnant women receiving at least two doses of tetanus-toxoid vaccine (TT2)
This indicator is calculated as:

Total TT2 + TT3 + TT4 + TT5 x 100
_________________________
Total # of live births

Where TT2, TT3, TT4, TT5 refer to the 2nd, 3rd, 4th, or 5th dose of tetanus-toxoid vaccine administered (WHO, 1999a and c).


From service statistics:
Number of doses of TT2 + TT3 + TT4 + TT5 given to pregnant women in a reference period (usually a year)

From population-based surveys:
Number of women giving birth during a reference period (e.g., five years) who report receiving at least two doses of tetanus-toxoid during their last pregnancy and number of live births in the same reference period

The number of live births serves as a proxy for the number of pregnant women.

Where data on the numbers of live births for the denominator are unavailable, evaluators can calculate total estimated live births using census data for the total population and crude birth rates in a specified area. Total expected births = population x crude birth rate

In settings where the crude birth rate is unknown, the WHO recommends using 3.5 percent of the total population as an estimate of the number of pregnant women (number of live births or pregnant women = total population x 0.035) [WHO, 1999a and c.]


Service statistics; population-based surveys


This indicator measures the percentage of women and births protected against tetanus at the time of delivery among clients in a given program or among the general population.

Neonatal tetanus is usually fatal. A woman immunized with at least two doses of tetanus toxoid according to the WHO schedule1 develops antibodies that protect her infant against tetanus in the first two months of life. Tetanus-toxoid immunization is therefore an integral part of the ANC package offered to women in most developing countries.

Many national HIS routinely collect this indicator to provide TT2+ coverage estimates for women attending facilities for ANC. Most large population-based surveys also collect data on self reported TT2+ coverage. Note: Variations in the methods used to measure TT2+ coverage, as well as in the definition of the numerator and denominator, give rise to differences in the magnitude and reliability of the estimates obtained. For example, service statistics record the total number of doses of a vaccine in the previous 12 months, whereas surveys tend to record the total number of women who report receiving at least two vaccinations during their last pregnancy in a reference period that may be up to five years.

Promoting clean delivery and cord care practices as well as ensuring that women are adequately immunized against tetanus prior to birth can prevent transmission of neonatal tetanus. TT2+ coverage should also be reported as well as the number of neonatal tetanus cases and the proportion of live births with a skilled attendant (as a proxy for clean births).

For prevention of neonatal and maternal tetanus, WHO recommends giving women a series of five doses of tetanus- toxoid vaccine with a minimum interval between each dose. Each dose increases the level and protection against tetanus. Each dose counts as a dose towards a five-dose schedule even if given before the recommended interval. A woman who receives five doses of tetanus toxoid is fully immunized and is protected against tetanus throughout her childbearing years.

Table III.E.3 WHO Recommended Tetanus-Toxoid Series

TT Time of Dose Given Level of Protection Duration of Protection
TTI At first contact NIL None
TT2 Four weeks after TTI 80% 3 years
TT3 At least 6 months after TT2 95% 5 years
TT4 At least one year after TT3 99% 10 years
TT5 At least one year after TT4 99% 30 years

Service statistics have the disadvantage that they may be incomplete or inaccurate (WHO, 1999a). They are also subject to a selection bias and are not representative of the general population, particularly when ANC coverage is low. However, they provide the only way of monitoring coverage on an annual basis and may be more reliable than self-reported data are.

Surveys provide the only means of obtaining population based coverage, but because surveys rely on selfreporting, they are subject to recall bias that is likely to increase with the length of the recall period.

Both approaches, however, underestimate the true extent of TT2+ coverage because both exclude doses of vaccine administered at times other than specified in the definition of the numerator even though the doses offer protection. For example, the doses for the childhood or mass-immunization campaign are omitted.


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