Eurosurveillance

ECDC

Effectiveness and Peculiarities of Immunoprophylaxis of Pertussis Among Children and Teenagers in Kaliningrad Oblast, Russia

 Rediger
  Published: 06.12.12 Updated: 06.12.2012 14:53:51

T. Grunicheva, E. Babura, Y. Gorbatova

Directorate of the Federal Service for Surveillance on Consumer Rights Protection and Human Well-Being in Kaliningrad Oblast (Rospotrebnadzor in Kaliningrad Oblast), Kaliningrad, Russia

Citation: Grunicheva T., Babura E., Gorbatova Y. Effectiveness and Peculiarities of Immunoprophylaxis of Pertussis Among Children and Teenagers in Kaliningrad Oblast, Russia. EpiNorth 2012; 13:40-3.

Summary
Analysis of pertussis incidence among the population of Kaliningrad oblast over the last 50 years proves the effectiveness of immunization measures taken in accordance with the national vaccination programme. During the pre-immunization period there were over 4 thousand cases of the disease registered annually in the region. In contrast, there have been approximately 30 cases per year during the last decade. The preventive measures implemented have been analyzed in relation to the current epidemiological situation in order to suggest additional improvements.

Introduction
In Kaliningrad oblast the scheduled immunization against pertussis was started in 1958. Immunization resulted in a drastic reduction (by hundreds of times) in the number of disease cases. In comparison with the pre-vaccination period, the intensive incidence rate of the disease decreased from 674.5 cases per 100,000 population in 1954 to 0.1 case per 100,000 population in 2010 (Fig. 1).

Fig. 1. Incidence of Pertussis in Kaliningrad Oblast in 1954-2011



The rapid decline in pertussis mortality was one of the most important positive results of immunization. No lethal outcomes of the disease have been registered for the last 15 years.
The goal of this article is description of the epidemiology of pertussis infection in Kaliningrad oblast through retrospective analysis and assessment of immunization measures.

Materials and Methods
Data from official statistical forms for registration of infection cases and reports on vaccination and coverage of children within the last decade were analyzed. In addition, results of epidemiological investigation of pertussis cases and serological monitoring of herd immunity in vaccinated persons were analyzed.
Confirmed and suspected cases of pertussis infection are diagnosed by medical officers working at health care facilities, medical institutions for children and teenagers, healthcare organizations or any other health institutions as well as medical practitioners providing any kind of medical service. All cases of the disease confirmed by laboratory diagnostics are subject to registration. Report forms with data on immunization are provided by all health care facilities that conduct immunization, regardless of their type, subordination and ownership form. Data from epidemiological surveillance of pertussis infection were analyzed for the period from 2001 to 2011.

Results
Despite of the evident positive dynamics in pertussis prevention, the epidemiological situation for the infection in the last decade cannot be easily assessed. One of its specific characteristics is the growing number of vaccinated children and teenagers among pertussis patients despite the high vaccination coverage (over 97.0%) (Fig. 2).

Fig. 2. Vaccination Coverage of Children against Pertussis in Kaliningrad Oblast, in 2001-2011

 

In 2001-2010, there were 517 cases of pertussis registered in Kaliningrad oblast. In the age structure of patients, alongside with the stably high incidence of the disease in the age group under 2 years (144 cases; incidence of 464.7 per 100,000 population), an increase in the incidence among older children was observed. Among children from 3 to 6 years there were 171 cases (incidence of 451.7 per 100,000 population) and among school children from 7 to 14 years there were 173 cases (incidence of 256.4 cases per 100,000 population).

Fig. 3. Age Groups (in %) of Pertussis Patients in 2001-2010



According to the immunization programme, 464 (89.6%) of the patients had been vaccinated according to the age and vaccination calender. A total of 118 children (25.4%) were fully vaccinated; 346 people (74.5%) were fully vaccinated and revaccinated. Fifty three non-vaccinated patients were registered (10.4%).
The older children who were fully vaccinated and revaccinated got infected due to insufficient length of post-vaccination immunity (waining of immunity). The evident drawbacks of the immunization schedule are demonstrated by the results of serological monitoring of immunity against pertussis among vaccinated persons.
Monitoring data from 2009-2010 show that 76.7% of children aged 4-5 years had an insufficient level of antibodies against pertussis; 10.9% of the children had no antibodies against the infection 1.5-2 years after revaccination. Seven to eight years 36.8% had no antibodies against pertussis while 55% of children aged 9-10 years had no specific antibodies to pertussis.
Assessment of herd immunity showed that majority of younger schoolchildren (of 7-10 years of age) had no post-vaccination immunity against pertussis. Only an insignificant number of children had protective level of antibodies.
Since immunization against pertussis can be effective only when the immunization intervals are strictly followed, any deviations from the schedule may result in an increase in the number of people susceptible to pertussis infection. In this regard, the vaccination intervals among vaccinated pertussis cases were investigated. Results indicate that there were deviations from the vaccination intervals in 52% of these cases.

Discussion
The results of mass vaccination of children against pertussis prove its effectiveness and demonstrate that the infection can be controlled. Serological monitoring data show that as people get older, their post-vaccination immunity against the infection decreases and this coincide with the increase in the incidence of the disease. Even school children who were fully vaccinated during early childhood get infected with pertussis.
Insufficient duration of post-vaccination immunity among children and accumulation of non-immune children by the age of 7 shift infection towards older age groups. Patients are becoming “older” with remaining high incidence registered among children under the age of 1 year. Further measures to prevent pertussis should include increasing vaccination coverage to at least 98% of the children under 1 year of age. In addition, the revaccination schedule against pertussis should be revised.

References:
1. Таточенко В.К., Озерецковский Н.А., Федоров А.М. Иммунопрофилактика-2011. Справочник.- Москва, 2011.
2. Лыткина И.Н., Чистякова Г.Г., Шаханина И.Л. Стратегия и тактика вакцинопрофилактики инфекционных болезней в Москве. // Эпидемиология и инфекционные болезни. – 1999.- №6.
3. Эпидемиологические аспекты коклюша в Российской Федерации. Особенности вакцинопрофилактики в современных условиях. Пособие для врачей. - МЗ РФ, НЦЗД РАМН. – 2005.


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