Immunity to measles virus in diverse population groups

Abstract

The aim of the study was to assess the measles immunity level among employees of medical organizations of various specialties, young subjects, and neonates. Materials and Methods. The measles immunity status was assessed for all the employees of St. Petersburg State Budgetary Healthcare Institution Maternity Hospital No. 10 (386 subjects), civilian medical staff of the clinics of the Military Medical Academy named after S.M. Kirov (Military Medical Academy) (1399 subjects), cadets of the Military Medical Academy (304 subjects) and 34 neonates. Laboratory testing was performed by using ELISA with test kits “VektoKor-IgG” (RF). Results. Medical workers displayed high total level of protection against measles virus serologically confirmed in 87.5% of the maternity hospital staff and 81.6% of the employees at the Military Medical Academy clinics. No differences in the immune status between the varying categories of medical personnel from the departments of various specialties were revealed. Lower population immunity was observed in the 20-40-year age group. Among the employees of the maternity hospital, the proportion of measles virus seropositive subjects aged 20—40 years was 75.9% (95%, CI 67.2—82.9%), 40—59 years — 91.5% (95%, CI 86.7—94.7%), 60 year and older subjects were all seropositive (95%, CI 94.6—100%). Dual vaccination did not guarantee emergence of effective measles immunity. The majority of seronegative subjects were dually vaccinated, hence, even in case of previous dual measles vaccination, it is necessary to perform a serological examination prior to recruitment to medical facilities. Females comprised more than 90% of medical workers. Therefore, women of fertile age previously dually vaccinated, but immunologically seronegative, are at risk of measles and intrauterine fetal infection, as well as the risk of its development is increased in vaccination age children. It was confirmed by demonstrating that as few as 70.6±15.3% of neonates were immune to the measles virus. The proportion of seronegative infants (29.4±15.3%) was comparable to that one in seronegative subjects aged 20—40 years (24.1±8.1%) working at the maternity hospital. Among the younger age group (aged 18—23 years) such as cadets of the Military Medical Academy, a significantly higher proportion of seronegative individuals was found — 48.3±5.6%, thereby increasing probability for measles outbreak therein. Conclusions. In order to eradicate measles, it is necessary to develop a screening program for detecting antibodies against measles among young and middle-aged subjects.

Keywords

• measles
• immunity
• health-care workers
• newborn children
• vaccination
• prevention