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VACCINE PROGRAMME, DELIVERY, SCHEDULE AND COVERAGE
high-quality, well-matched vaccines able to elicit high levels of protection is essential.
will be involved in the implementation of the vaccination programme.
To calculate vaccine coverage, the availability of reliable data is of utmost importance, and in this regard it is essential that a simple information system is implemented for this purpose.
Information on the number of animals actually vaccinated (the numerator) can also be acquired from several sources.
Vaccine coverage can be assessed based on the records of the vaccination cards and the registration book for batches and doses (Annex 1) that should be made available at local distribution centres. Vaccine coverage in eligible animals after the last round of vaccination may be calculated from: (Number of animals vaccinated/Number of animals eligible for vaccination) × 100 where ‘number of animals vaccinated’ is the numerator and ‘number of animals eligible for vaccination’ is the denominator. If the purpose is to calculate the vaccination coverage over an entire susceptible population, the denominator of the proportion has to be replaced with the total number of animals and becomes: (Number of animals vaccinated/Number susceptible animals in the population) × 100
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There are several ways of obtaining the information required to estimate vaccine coverage (7). Although a considerable investment and effort is required to obtain reliable and detailed data, simple methods are sometimes possible. More detailed data allow greater investigation of gaps in vaccine coverage, for example assessing coverage for different geographical or administrative units and per age category, and may identify under-protected subgroups. The denominator should reflect the carefully defined target population, i.e. those eligible for vaccination or alternatively the total susceptible population. If the denominator estimate is incorrect, coverage estimates will also be incorrect. In countries with a national database of animals and where the animals are individually tagged, obtaining this figure may be relatively simple. In countries where no national databases are available, livestock census data may be available. If not, a survey may be needed to estimate this figure. As a last resort, the actual number of animals eligible and ineligible for vaccination can be assessed at the time of vaccination, although some preliminary approximate information is needed in advance to decide the number of doses to be distributed across the peripheral centres that Foot and mouth disease vaccination and post-vaccination monitoring. Guidelines
Foot and mouth disease vaccination coverage is often described as the number of doses of vaccine distributed (i.e. the number of doses sent out to the vaccination centres) divided by the estimated population size (distributed method). Although easy to perform, the distributed method has limitations, and in order to obtain reliable estimates it is vital that (i) registration books for batches and doses are accurately compiled, and (ii) estimates of the animal population targeted for vaccination are accurate. Sub-regions with low coverage may not be identified if local vaccine distribution statistics are not available. If records describe only which village, farm or district was vaccinated and not how many animals, inaccuracies may be encountered, as not all animals within a unit may be vaccinated, particularly in backyard settings. If vaccines are provided by different sources (e.g. public and private sector), it is important that both are included in the numerator. The administered method is identical to the distributed method, except that records of doses administered to animals in the field are used, not doses distributed to vaccination centres. Individual animal vaccine history may also be recorded; this allows calculation of the proportion of animals vaccinated within a certain time period or the number of doses received by the animals over their lifetime. This requires excellent data recording and management capabilities. Vaccine coverage should be regularly monitored and verified. Detailed examples of how to record and analyse vaccination data on an on-going basis are given in Annex 2. Overall progress should be reviewed at least annually and in conjunction with the information obtained from population immunity studies, especially those directed at looking at immunity in the vaccinated population (see section 3.5).
2.6 Checklist for implementing vaccination – If feasible, start vaccination on a small scale and build up the programme as local experience matures. – Establish clear objectives and targets. – Decide which species and population to vaccinate.
