Academic journal article Central European Journal of Public Health

Estimation of the Population Susceptibility against Measles in Slovakia

Academic journal article Central European Journal of Public Health

Estimation of the Population Susceptibility against Measles in Slovakia

Article excerpt

INTRODUCTION

(ProQuest: ... denotes formulae omitted.)

Measles is a highly contagious, exanthematous disease. It is caused by morbillivirus within the family Paramyxoviridae (1). Measles had been considered one of the most frequent childhood diseases in the past. Since the introduction of mass vaccination in 1969 a permanent decline in incidence has been observed, which has been only interrupted by occasional outbreaks. No endemic and only few imported cases have been reported in Slovakia since1999 until the present time.

Vaccination by attenuated vaccine induces both, humoral and cellular responses. Even if these responses are of lower magnitude and shorter duration compared to those following wild-type measles virus infection, the antibody titers remain still sufficiently high to provide effective protection (1). However, recent research findings suggest that measles vaccine protection wanes with time, creating a real concern that proportion of individuals in a cohort who retain protective antibody levels following vaccination might be compromised over time. Thus, the effect of waning immunity could potentially lead to an increase of susceptible individuals in the population concerned (2-9).

Despite the fact that in the recent years measles cases have not occurred in Slovakia, it still remains a threat to the current or near-future population. Since the last national seroprevalence survey was performed in 2002, the current status of the population susceptibility to measles is uncertain. The aim of this work is to build a model of waning immunity and incorporate it into an age cohort model of the Slovak population in order to estimate the fraction of individuals susceptible to measles in 2015.

MATERIALS AND METHODS

Our approach is based on a cohort model. By the term cohort we understand a group of individuals born in the same year. We assume that the Slovak population can be divided into 100 age cohorts. The inputs of our model are the administrative data on vaccination (10), information from the national seroprevalence survey of2002 (11) and the demographic data on the age structure of population (12).

Data on Vaccination within Administrative Control of Vaccination

A two-dose measles vaccination schedule has been used between the years 2002 and 2015. The data on vaccination considered in this study are taken from the yearly reports of administrative controls of vaccination in Slovakia (10). These controls are based on personal inspections of the paediatricians' records performed by personnel of regional public health authorities. Administrative data on vaccination coverage were obtained from numbers of vaccinated and all children of the given age in the respective catchment area. The available data contain the 1 st dose (MCV1, provided to children between 15-18 month of life), immunization coverage for cohorts born after 1992, and the 2nd dose (MCV2, provided to children in the 11th year of life), vaccination coverage for cohorts born after 1983. If the given cohort has been checked more than once, we have taken into consideration the most recent information, i.e. for the first dose (MCV1) in cohorts 1992-2003 vaccination coverage of 4-year-old children, and in cohorts 2004-2012 vaccination coverage of 3-year-old children. Similarly, we have considered for the second dose (MCV2) in cohorts 1983-1993 vaccination coverage of 11-year-old children, and in cohorts 1994-2003 vaccination coverage of 10-year-old children (Fig. 1).

Seroprevalence Survey 2002

The seroprevalence survey 2002 consisted of 3,640 individuals, among them 1,537 children up to 15 years and 2,103 subjects from the population older than 15 years (11).

Unfortunately, only aggregate data on seropositivity/negativity for particular age cohorts are available from the seroprevalence survey 2002.

For the purposes of this study we understand susceptible (S) to be the synonym to seronegative. Similarly, immune (resistant/ recovered (R)) shall be equivalent to seropositive. …

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