Factors affecting the seroconversion rate of 12-month-old babies after the first injection of measles vaccine in the southeast of Iran

Abstract

Within the past few years, several measles outbreaks have occurred in the southeast of Iran. To learn about the effectiveness of the immunization services for producing a serologic response against measles, this follow-up study was designed and implemented in the southeast of Iran. In Iran, all routine immunization services provided by the public sector are free of charge. The follow-up study was designed and implemented in 5 Urban Health Centers located in 3 districts of Sistan-va-BaluchestanProvince, Iran. In the pre-vaccination phase, 270 12-month-old babies were blood sampled; and in the post-vaccination phase, 4 to 7 weeks after Measles, Mumps, Rubella (MMR) vaccination, 236 of them were blood sampled (34 dropouts), and their sera were tested for IgG anti-measles antibodies, using indirect ELISA, in the National Reference Measles Laboratory. Out of the 236 participants, who had been blood sampled in the post-vaccination phase, 10 (3.7%) were excluded from the calculations of seroconversion rate, because they had protective levels of antibody before the vaccination. The seroconversion rate for the remaining 226 participants was 91.2% (95% confidence interval: 86.7 to 94.5). Among the variables studied, stunting (height-for-age z-score < -2) showed a strong relationship with the remaining seronegative after the vaccination (odds ratio = 5.6; 95% confidence interval: 1.7-18.2). The chance of seroconversion was inversely related to the mothers' levels of education (up to 9 y of education vs. above nine years) (odds ratio = 0.2; 95% confidence interval: 0.06-0.4). In the study population, the seroconversion rates for anti-measles antibodies after MMR vaccination are acceptable, even though in order to achieve the elimination goal, higher standards need to be achieved.

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

“…Therefore, vaccinerelated factors such as lack of adequate potency of vaccine because of using more thermo-labile strains, inadequate control of cold chain shipment, storage, use, and other probable factors may be responsible [45][46][47]. Our assumption regarding the inadequate potency of vaccine is based on the results of studies that were designed to investigate the immunogenicity of MMR vaccine currently used in Iran [48][49][50][51][52][53]. The majority of these studies showed lower rates of seroconversion following the first and/or the second doses of MMR vaccine after the age of 12 months (Table 5).…”

Measles and Rubella Serosusceptibity among Population Vaccinated with Different Schedule: The potential impact on Measles-Rubella elimination in Iran.

“…Therefore, vaccine-related factors such as lack of adequate potency of vaccine because of using more thermolabile strains, inadequate control of cold chain shipment/storage/ and use, and other probable factors may be responsible (45)(46)(47) . Our assumption regarding the inadequate potency of vaccine is based on the results of studies that were designed to investigate the immunogenicity of MMR vaccine currently in used in Iran (48)(49)(50)(51)(52)(53) . The majority of these studies showed lower rates of seroconversion following the rst and/or the second doses of MMR vaccine after the age of 12 months ( Table 5).…”

Measles and Rubella Serosusceptibity Among Population Vaccinated with Different Schedule of Vaccination: The Potential Impact on Measles Elimination in Iran.

“…After mass MR immunization program, many seroprevalence studies among MR vaccinated subjects were conducted. Results revealed that nearly 87-99% of vaccines got seroprotection against measles and rubella (25)(26)(27)(28) .…”