Level of measles herd immunity assessed in hospital medical workers within a framework of the state measles elimination program

Abstract

Within a framework of the state measles elimination program, in April, 2018 a level of measles herd immunity was assessed in 1899 Moscow hospital medical workers aged from 19 to 69 years and older. All subjects enrolled in the study were vaccinated against measles or recovered after measles infection. Serum samples were collected from subjects and examined by ELISA for measles IgG antibodies with the Vector-Best IgG-measle test system (Russia). It was found that 278 (14.6%) and 1621 (85.4%) subjects were seronegative (< 0.18 IU/mL) and seropositive (> 0.18 IU/ml), respectively. Age-related group distribution of 1855 serum samples revealed that percentage of seronegative subjects was in: aged 19—23 years was -38.5%; 24-28 and 29-33 years - 22.2%; 34-38 years - 27.5%; 39-43 years - 25.8%; 44-48 years - 16.8%; 49-53 and 54-58 years — 8.6% and 8.3%, respectively; 59-63 years old — 4.9%; 64-68 and over 69 years old — 0%. Moreover, mean level of measles IgG antibodies increased proportionally to age of medical workers from 0.58 IU/ml (19-23 years) to 2.94-2.72 IU/ml (64-68 and over 69 years). The data obtained indicate that a cohort of measles susceptible subjects (from 38.5% to 16.8%), respectively, is identified among young and middle age (from 19 to 48 years) individuals. It is assumed that two-dose measles vaccination in childhood does not contribute to the long-term preservation of protective levels of measles antibodies, thereby justifying a need to administer a three-dose measles vaccine.

Keywords

• collective immunity
• measles
• antibodies to measles virus