2019–2020 measles in the Republic of Guinea: epidemic features and herd immunity

Introduction. In connection with the Ebola epidemic in the West African countries, including the Republic of Guinea, a failure in implementing measles immunization program was noted. A proportion of measles seronegative subjects in 2017 was 52.4% of total examined individuals. In 2018, a high proportion of measles cases among children aged 1–5 years (61.6%) was identified. In order to stop the 2018 outbreak, the Supplemental Immunization Campaign was conducted in the Konakri and Nzerekore prefectures in the Republic of Guinea. The aim of this study was to examine the 2019–2020 measles epidemic situation and assess the measles population immunity in the Republic of Guinea. Materials and methods. Measles-specific antibodies were examined in 1697 blood serum samples collected from residents of different regions of the Republic of Guinea, aged from 7 months to 76 years, obtained in 2019–2020, and tested retrospectively. The ELISA test systems Anti-Measles Virus ELISA (IgM) Euroimmun and Anti-Measles Virus ELISA (IgG) Euroimmun (Germany) were used. The presence of serum IgM measles antibodies was considered as acute measles infection. Statistical analysis was performed using the software package Statistica 6.0. Results. Blood sera (n = 638) were tested for IgM-measles, and in 46.6% of cases the diagnosis was confirmed by laboratory tests. The biggest proportion of the total cases (61.6%) was found in children aged 1–4 years. The second most important age group was 5–9 years of age, the third is children under 1 year: 18.5% and 11.8% of the total number of patients, respectively. Measles infection was registered in vaccinated patients in 7.4% of the total number of laboratory-confirmed cases. 1059 subjects were examined for IgG measles antibody. The lowest seroprevalence rate was found among children under 4 years of age (47.8%). The highest (85.5%) was found among subjects of 40 years old and older. Conclusion. Measles in GR remains a poorly controlled infection. As in the previous years of observation (2017–2018), children under 5 years of age are the most vulnerable cohort of the population, despite the 2018 DI campaign conducted in a number of GR territories. More problems with the measles control in the Republic of Guinea are expected in the period from 2021, as along with the COVID-19 epidemic, Ebola is repeatedly registered in the country. The Republic of Guinea particularly requires assistance from the international community to implement the WHO measles elimination program on a global scale.