Collective Immunity to the Measles, Mumps, and Rubella Viruses in the Kyrgyz Population.

UNLABELLED

Specific prevention of measles, mumps, and rubella (MMR) is the main prerequisite for a radical reduction in the incidence of these infections in the Kyrgyz Republic (KR). An increase in the number of seronegative individuals observed in recent years has led to an increase in measles incidence. This is directly related to a decrease in collective immunity, which provides protection for the population only in conditions of a high density of immunized individuals and their uniform distribution in the population. The only way to estimate the number of immunized individuals is by conducting serological surveys of collective immunity.

AIM OF THE STUDY

The aim was to study the level of collective immunity to the MMR viruses in the KR.

MATERIALS AND METHODS

This study involved a cohort of 6617 residents (volunteers) aged 1 to 70 years, formed in accordance with the Rospotrebnadzor program "Assessment of collective immunity to vaccine-preventable and other relevant infections" and stratified by age and region of residence. During the study, participants filled out a questionnaire and gave venous blood samples to determine IgG antibodies to MMR viruses (ELISA using certified Russian test systems).

RESULTS

In December 2023, collective immunity ensured epidemiological well-being only with respect to rubella. The volunteer seropositivity was 94.2% (95% CI: 93.7-94.8). The average measles seropositivity was 78.9% (95% CI: 77.9-79.9). It was significantly lower in children aged 1-17 years and significantly higher than the cohort average in individuals aged ≥18 years. The average mumps seropositivity was 76.4% (95% CI: 75.3-77.4), with the minimum level noted among individuals aged 12-29 years (63.8%; 95% CI: 61.4-66.2). The maximum levels of mumps seropositivity were noted among children aged 6-11 years and older adults who had likely experienced mumps (50-70 years). Seroprevalence distributions by activity correlated with age distributions (all infections).

CONCLUSIONS

The system of targeted prophylaxis of vaccine-preventable infections adopted in the KR has contributed to the formation of a high level of rubella collective immunity and, to a lesser extent, measles and mumps immunity. The recent trend towards increases in measles and mumps incidence in the KR requires additional efforts to increase collective immunity to these infections.