Survey in Tajikistan reveals good protection against many diseases except diphtheria

Results of a sero-epidemiological survey of randomly selected persons in Tajikistan, to determine susceptibility to vaccine-preventable diseases, have shown that despite good protection against polio, measles, rubella and tetanus, almost half of the general population aged 1-24 years lacks fully protective levels of diphtheria.

A roundtable to share the survey results and discuss future steps to prevent potential outbreaks in the country was held on 27 September, 2011 in Dushanbe, Tajikistan, organized by the WHO Office in Tajikistan and the Ministry of Health of Tajikistan. The sero-survey was conducted following the polio outbreak in 2010.

Recent polio outbreak overcome

Deputy Minister of Health, Dr Mirzoev A.S, welcomed all participants and reminded everyone of the magnitude and devastation of the recent polio outbreak in the country; the largest outbreak of polio in the world since 2005. The Deputy Minister was followed by WHO Country Representative, Dr Pavel Ursu, who emphasized that, supporting the Ministry of Health, the coordinated response of all agencies resulted in the control of the outbreak in a short period of time. Dr Ursu also drew attention to threat imposed by the recent polio cases in China, a country that shares a long border with Tajikistan. Thanking the partners and stakeholders for retaining the European Regional Polio free status, the WHO/Europe Regional Adviser for Vaccine Preventable Diseases and Immunization, Dr Rebecca Martin, highlighted that the most important issues for the country at the moment are to strengthen routine immunization and improve surveillance of communicable diseases.

Supplementary immunization activities for diphtheria needed

Technical presentations from the Centers for Disease Control and Prevention, Atlanta, USA, the Regional Diptheria Reference Laboratory at the WHO collaborating centre at the Health Protection Agency in the United Kingdom, and the Tajikistan National Measles and Rubella Laboratory, and subsequent discussions concluded that despite good protection against polio, measles, rubella and tetanus, almost half of the general population aged 1-24 years lacks fully protective levels of diphtheria. More than 20% of the population surveyed has no detectable diphtheria antibodies. Immunity is particularly low among persons aged 10-19 years and among the Lulli (Gypsy) community.

There were major diphtheria outbreaks in Tajikistan from 1993-1999 with more than 10,000 cases and over 800 deaths.  Many of those cases were among older children and adults. The outbreak was then controlled after two rounds of supplementary immunization activities (SIAs) in 1995 (3-50 yrs) and 1996 (15-50 yrs).   Alongside concerns regarding potential future outbreaks of diphtheria in Tajikistan, there also exist weaknesses with diphtheria surveillance and laboratory capacity in the country.

The general assumption is that the immunity gap for diphtheria, across a wide age range and in all regions, is the result of long-standing problems with routine immunization delivery. This demonstrates the need to strengthen routine immunization and carry out an SIA for diphtheria as a one-time measure to close the immunity gap and prevent future outbreaks.