N. Rogushina1, O. Samodova1, L. Titova1, R. Buzinov2, L. Grishina2
1Northern State Medical University, Arkhangelsk, Russia
2 Directorate of the Federal Service for Surveillance on Consumer Rights Protection and Human Well-being (Rospotrebnadzor) in Arkhangelsk oblast, Arkhangelsk, Russia
Citation: Rogushina N. L., Samodova O. V., Titova L. V., Buzinov R. V., Grishina L. N. Rubella epidemilogy and rubella immunity in Arkhangelsk oblast, Russia, 1979-2007. EpiNorth. 2009;10(1): 12-17.
Research addressing rubella infection and the evaluation of specific immunity among women of childbearing age are relevant due to the high incidence of rubella and the lack of clear data about the prevalence of congenital rubella syndrome. Five hundred women from Arkhangelsk oblast were tested for rubella virus-specific immunoglobulin G using enzyme-linked immunosorbent assay (ELISA). The results showed that 7.2% of the women were seronegative to rubella virus.
Rubella is a disease that develops as a congenital or acquired infection. A typical acquired rubella infection has mild symptoms and is characterised by a macular-papular rash, a slight increase of temperature, absence of intoxication and enlarged occipital and posterior auricular lymph nodes. The source of infection is a person with clinical symptoms or asymptomatic infection. Asymptomatic infection is of special concern regarding the detection of rubella among susceptible pregnant women (1, 2).
Congenital rubella is characterised by severe clinical symptoms and long-term consequences. Rubella virus infection acquired during the first trimester of pregnancy can cause spontaneous miscarriages and severe birth defects, and thus the social and economic burden of this infection is high (3-10). WHO and UNICEF have developed a strategic program for the prevention of congenital rubella in the European region. The goal is to decrease the incidence of congenital rubella to less than 1 case per 100,000 live births by 2010 (1). The number of women of childbearing age who are susceptible to rubella should be low in order to reach this goal. According to the published national data for Russia, approximately 11% of women are susceptible to rubella, while in some regions of Russia 30% of women may be susceptible (4, 5).
Mass vaccination of the population is the main way by which congenital rubella can be prevented (11, 12). Rubella vaccination has been included in the National Vaccination Programme of the Russian Federation since 1997 and mass vaccination started in 2000 (13). The efficacy of the vaccines used in the Russian Federation is 94.3-99.7% (14). Specific immunity developed after immunization is determined by the quality of the vaccine administered and by individual immune response which, in most cases, is genetically determined. It is well known that 5-10% of vaccinated and 5% of re-vaccinated individuals do not develop protective immunity and are at risk of rubella infection despite timely vaccination (11).
The official rubella registration in Arkhangelsk oblast began in 1979. All cases with typical clinical symptoms were recorded, with and without laboratory confirmation. Rubella vaccination has been performed since 2000 in this oblast. During the pre-vaccination period, an increase in incidence was recorded every 4-5 years.
The official registration of congenital rubella syndrome (CRS) in the Russian Federation was introduced in 1991. According to WHO estimates, CRS can annually be reported among 0.13% of all patients with acquired rubella. (1). Data indicate only isolated cases ranging from 0 to 11 cases per year of this disease throughout the country. During 1979-2007, congenital rubella was not registered in Arkhangelsk oblast.
The purpose of this study was to investigate and analyse the epidemiology of rubella and determine specific immunity to rubella virus among women of childbearing age in the Arkhangelsk oblast.
Materials and methods
A cross-sectional study was conducted from March 2006 to February 2008 among randomly selected women between 15 and 39 years of age without acute disease or relapse of chronic pathology at the time of the study. Samples were collected at the polyclinic of the Infectious Disease Centre of Arkhangelsk. Medical history data were collected using anonymous questionnaires completed by the women. The questionnaire included the following questions: place of residence, age, prior history of exanthematous infections, rubella history, age when rubella was registered, laboratory confirmation of rubella, rubella vaccination history and the date of immunisation.
Immunoglobulin G-specific antibodies (IgG) were detected using an ELISA test (VectoRubella-IgG-strip, Joint Stock Company “Vector-Best”, Russia). Quantitative assessment of anti-rubella IgG was performed on serum samples and the optical density values were converted to U/mL using the formula provided. According to the manufacturer’s instructions, rubella antibody titres equal to or greater than 15 U/mL are considered to be protective. The data were analysed using Statistica software package (Version 6.0).
We also analysed official surveillance data from the Directorate of Rospotrebnadzor.
Rubella-specific immunity was measured in 500 women aged 15 to 39 years. The average age of study participants was 22 years; 198 women (40%) were aged less than 20 years, 223 women (44%) were aged from 21 to 25 years, 48 (10%) women were aged from 26 to 30 years, 31 (6%) women were aged from 31 to 35 years. Two hundred and seventy six women (55%) lived in Arkhangelsk city, and 224 (45%) women lived elsewhere in Arkhangelsk oblast. Information obtained from the questionnaires indicated that the most common exanthematous infection experienced was varicella (318 women; 64%). Scarlet fever was reported by 25 (5%) women, measles 19 (4%), infectious mononucleosis by 4 (1%), and yersiniosis infection by 2 (0.4%) women. A prior history of rubella was reported by 134 (27%) women. One hundred and one (81%) of 134 respondents reported the age at which rubella was registered; rubella occurred before the age of 5 years in 41% of the women, from 5 to 10 years in 33%, and after the age of 10 years in 27% of the women.
According to the ELISA results, rubella-specific immunoglobulin G antibodies were found in 464 of the women (93%); specific antibodies were not present in 36 (7%) of the women.
The incidence in Arkhangelsk oblast was 659, 471 and 232 cases of rubella per 100,000 population in 1985, 1990 and 1995, respectively (Fig. 1). The highest incidence was reported in 1999 with 1211 cases per 100,000 population. After each increase of rubella incidence, a decrease was reported. The lowest incidence was reported in 1994 and 1997, and was 93 and 63 per 100,000 population, respectively. For certain years, the rubella incidence in the Arkhangelsk oblast was lower than in the Russian Federation. However, in 2000, 2004 and 2007, the incidence in our region was 1.3, 1.2, and 3.7 times higher than the incidence in the Russian Federation despite immunisation.
Fig. 1. Rubella incidence (per 100,000 population) in the Russian Federation and Arkhangelsk oblast, 1979-2007
During 2005-2006, a tendency towards a decrease in the incidence of rubella was noted in the Russian Federation and Arkhangelsk oblast. According to the data from the Directorate of Rospotrebnadzor in Arkhangelsk oblast, rubella vaccination coverage among children aged 24 months was less than 1% in 2000, increased to 90% in 2002 and 2003, and has remained at 95% or higher from 2005 (Fig. 2).
Fig. 2. Rubella incidence (per 100,000 population) and vaccination coverage among children aged 24 months in Arkhangelsk oblast, 2000-2007
The age structure analysis indicated an increase in the incidence of rubella from 6.7% to 57.0% among adolescents and adults above 15 years of age from 2000 to 2007. The increase in the proportion of adults with rubella is apparently caused by the high vaccination coverage in the children population (Fig. 3).
Fig. 3 Age structure of rubella cases in the Arkhangelsk oblast among children aged less than 14 years and adults, 1998- 2007
We believe that the decreasing incidence among children could be a result of vaccination.
The increasing incidence of rubella among adults causes concern as an increasing number of cases among women of childbearing age may result in an increase in the number of children born with CRS. Among the study women, 78 (16%) were vaccinated against rubella; specific antibodies were not present in 4 (5%) of the vaccinated women. It is notable that rubella virus IgG antibodies were found in 276 (93%) of 298 women who did not report a prior history of rubella and were not vaccinated against rubella. This may be explained by an atypical form of rubella that does not present with typical clinical symptom such as rash. Six (5%) of 134 women who reported a prior history of rubella were seronegative. In the group of women reporting a prior rubella history, the infection was diagnosed based on clinical data without confirmatory laboratory tests.
We conclude: 1) In Arkhangelsk oblast, 7% of women of childbearing age were seronegative to rubella virus and were thus at risk for infection and CRS to their foetus. 2) After a single immunisation, 5% of the vaccinated women did not have rubella-specific antibodies. 3) A tendency toward an increase in the incidence of rubella among adolescents and adults was noted after the introduction of immunisation of children.
We recommend that the laboratory confirmation should be performed for the diagnosis of acquired rubella due to the high percentage of asymptomatic rubella infections and that immunisation of adult population must be continued.
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