Number of neonatal tetanus cases
The number of neonatal tetanus (NT) cases in a given year, in a defined population, including both suspected and confirmed cases
A suspected case: any neonatal death between 3-28 days of age in which the cause of death is unknown; or any neonate reported as having suffered from NT between 3-28 days of age and not investigated.
A confirmed case: any neonate with a normal ability to suck and cry during the first 2 days of life; and who between 3-28 days of age cannot suck normally and becomes stiff or has convulsions (i.e., jerking of the muscles) or both.
The basis for case classification is entirely clinical and does not depend on laboratory confirmation. NT cases reported from hospitals are considered confirmed (WHO, 1999a).
Number of NT cases or deaths
Population based NT mortality surveys; neonatal tetanus surveillance systems; and population-based surveys (TT2+ coverage, number of live births)
NT is a major public health problem in the developing world. Maternal and NT have been among the most common lethal consequences of unclean deliveries and umbilical cord care practices. When tetanus develops, mortality rates are extremely high, especially when appropriate medical care is unavailable. WHO estimates that in 2008 (the latest year for which estimates are available), 59,000 newborns died from NT.
The Maternal and Neonatal Tetanus (MNT) Elimination Initiative aims to reduce the number of maternal and neonatal tetanus cases to such low levels that MNT is no longer a major public health problem. Unlike polio and smallpox, tetanus cannot be eradicated (tetanus spores are present in the environment worldwide), but through immunization of pregnant and women of reproductive age and promotion of more hygienic deliveries, MNT can be eliminated (defined as less than one case of neonatal tetanus per 1000 live births in every district).
Because the case fatality is very high in most developing countries, the number of neonatal tetanus cases is often based on actual or estimated numbers of NT deaths. In countries with tetanus toxoid immunization coverage (TT+) of over 90 percent and a clean delivery rate over 80 percent, the number of neonatal tetanus cases is taken as the number of neonatal tetanus deaths reported.
In countries with lower coverage, an estimate of the number of NT cases is based on an estimate of NT deaths calculated from the number of live births, the neonatal tetanus mortality rate (NTMR), TT2+ coverage, and vaccine efficacy.
Some countries occasionally conduct NT mortality surveys, although most countries with a high proportion of neonatal tetanus deaths carry out routine surveillance in “high risk” areas. Unfortunately, surveillance systems function poorly, and NT continues to be seriously underreported. Community-based NT mortality surveys, for example, suggest that routine surveillance systems detect only two to eight percent of all cases (WHO, 1994b). For this reason, WHO recommends using the following calculation in most settings.
|Live births x NTMR x # of NT deaths in 1 year= (1-TT2+ x VE)|
NTMR = the baseline Neonatal Tetanus Mortality Rate (mortality rate in unvaccinated cases); TT2+ = Tetanus-toxoid-immunization coverage; and VE = Vaccine efficacy (estimated as 0.95).
The NTMR used is the latest value reported in each country where a nationwide survey was undertaken; if no surveys were conducted, a rate of 1, 5, 10, 15 cases per 1000 live births is allocated on the basis of the NTMR reported in countries with similar risk factors. In Latin America the WHO Regional Office (AMRO) uses a correction factor for the sensitivity of the surveillance system to adjust for the numbers of reported neonatal tetanus deaths (WHO, 1994b).
Countries with NT surveillance systems assess their progress annually. Demographic surveys, providing neonatal mortality at 4-14 days on a 3-5 year basis, serve to evaluate surveillance data.
A number of caveats warrant mention. First, this indicator reflects the overall magnitude of the problem of NT deaths but does not offer a precise estimate because of serious underreporting from surveillance data and because of the many assumptions inherent in the WHO calculation. Second, because this indicator is reported as a number rather than as a proportion, countries with lower rates of NT deaths but larger populations will rank ahead of countries with proportionately higher deaths rates. Third, aggregate figures at a national level may disguise pockets of high risk in certain subgroups (for example in rural populations or low-caste groups).
Surveillance systems reporting the number of NT cases should also give the percent completeness of reporting (number of NT reports received/the number of reports expected in the same time period). NT deaths should also be reported in conjunction with TT2+ coverage and the proportion of live births with a skilled attendant (as a proxy for proportion of clean deliveries).
In countries where NT is a recognized problem, population-based surveys may provide information on levels and trends of neonatal mortality. These surveys provide information on neonatal mortality at 4-14 days, which is a sensitive indicator of NT mortality (Boerma et al., 1996).
Maternal and neonatal tetanus elimination. WHO, http://www.who.int/immunization_monitoring/diseases/MNTE_initiative/en/index.html. Accessed June, 2011.