Measles Outbreak in a Rural Population in Bahar District, Hamadan Province, West of Iran in 2018

Investigation of the Seroprevalence of Antimeasles Immunoglobulin G Antibody in Students at Shiraz University of Medical Sciences

Measles is an acute, highly contagious disease with a high mortality rate in children. Although vaccination has reduced measles incidence, outbreaks still occur. Therefore, in this study, we aimed to investigate the frequency of antimeasles immunoglobulin G (IgG) antibody (Ab) among students at Shiraz University of Medical Sciences (SUMS). Four hundred fifty SUMS students were enrolled in this cross-sectional study. Information on demographics and measles vaccination history was collected using a questionnaire. Participants were divided into two groups, including A and B, according to routine doses of measles vaccine and the national measles/rubella immunization program. The antimeasles IgG Abs were tested using a commercial Enzyme-Linked Immunosorbent Assay Kit. Participants ranged in age from 18 to 48 years, with a mean age of 22.2 (±4.3). Fifty percent of the subjects were male. Our results showed that 63.6% of the cases were positive for antimeasles IgG Abs. The seroprevalence of IgG Abs between groups A and B did not differ significantly (p = 0.612). There was also no significant correlation between the seroprevalence of antimeasles IgG Abs and the age (p = 0.43) or sex (p = 0.24) of the subjects. The results showed that the frequency of antimeasles IgG Abs is lower than required to prevent the measles virus from circulating. Therefore, a booster vaccination may be necessary.

Measles and rubella serosusceptibity among population vaccinated with different schedules: the potential impact on measles-rubella elimination in Iran

BACKGROUND

Iranian children were vaccinated with the scheduled two doses of monovalent measles vaccine (mMV) from 1984. In December 2003, a nationwide campaign of measles-rubella (MR) immunization was established to vaccinate 5-25 year- old individuals. In 2004, the mMV was replaced with measles- mumps- rubella (MMR) vaccine. Despite the high vaccination coverage, the outbreaks of measles still occur in the country. In this Study, the MR immunity status of various age groups, vaccinated with different schedules was investigated, and the immunologic response of seronegative subjects to revaccination was examined.

METHODS

This cross-sectional study was conducted among 7-33-year-old healthy individuals with a documented history of measles vaccination from November 2017 to June 2018. The subjects were categorized as follows: group A, including 20-33 year-old individuals; vaccinated with 1-2 doses of mMV at ages 9 and 15 months, and revaccinated with MR, group B, including 15-19-year-old individuals, vaccinated with two doses of mMV at 9 and 15 months of age, and received additional dose of MMR upon school entrance, group C, including 11-14 year-old individuals, vaccinated with two-doses of MMR at the ages of 15 months and 6 years, and group D, including 7-10 year-old individuals vaccinated with two-doses of MMR vaccine at the ages 12 and 18 months, respectively. Levels of antimeasles- antirubella IgG antibodies in the collected sera were measured. Also antimeasles- antirubella IgM and IgG of seronegative individuals were reexamined at 4-6 weeks after MMR revaccination. The collected data were analyzed using descriptive statistical methods.

RESULTS

A total of 635 individuals were investigated in this study. Group A, 98; group B, 295; group C, 139; and group D, 103 persons. Overall, 12.3 and 18.4% of the population were seronegative for measles and rubella antibodies. This rate varied greatly between the 4 groups: group A, 0/0-2%; group B,15.2-25.0%; group C,11.5-17.2%; and groupD,14.6-18.4%. After revaccination, 92 and 94.9% of seronegative individuals showed IgG response to measles and rubella vaccines, respectively.

CONCLUSION

Despite the high coverage rate of M-R containing vaccines, a significant number of vaccinated subjects were seronegative for measles and rubella, possibly because of secondary vaccine failure; this may negatively affect measles-rubella elimination targets in the country. If these findings are confirmed in similar future studies, a more robust regional/national supplementary immunization activity will be considered.