Immunogenicity and safety of standard-titer AIK-C measles vaccine in nine-month-old infants

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

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.

Antigen-specific lymphocyte proliferation assay and virus neutralization test for measurement of measles-specific immunity in 15-19 years old high school students in Tehran, Iran

Limited information is available concerning the role of measles-specific cell mediated immunity as a correlate of long-term protection from measles infection. Although serological responses are determined in epidemiological studies and high antibody titer is a good indicator of protection, the role of Cell-Mediated Immunity (CMI) has to be defined more clearly. In this study, Lymphocyte Proliferation (LP) and Viral Neutralization Test (VNT) were used in order to measure measles-specific cellular and humoral immune responses of 100 high school students in Tehran. From total number of subjects studied, 33 were girls and 67 were boys and all were in good health. Of these, 77 had protective neutralizing measles antibody titers and 23 did not have such titer. The results of LP showed that 89 subjects had protective cellular immune responses and 11 did not. A quantitative relationship between humoral and cellular immune responses was not observed. These findings suggest that measles-specific protective CMI is measurable for longer time in comparison to humoral immunity. These data suggest that LP responses may be better sustained than antibody titers in some children.

The challenge of improving the efficacy of measles vaccine

Despite a safe and effective measles vaccine, measles still claims an estimated 800,000 lives per year mostly among children in developing countries. This paper deals with strategies to improve vaccine efficacy and prevent unnecessary deaths, including considerations of one dose at 9 months strategy for developing countries, strain of vaccine, potency and number of doses of measles vaccine. After more than 20 years of measles immunisation in the developing world, the epidemiology of measles is radically changed, and the absence of measles epidemics might lead to waning immunity due to less clinical and subclinical infections boosting the antibody level. An increasing proportion of mothers are vaccinated, thus transferring a lower maternal antibody level to their infants who will be susceptible to measles at a younger age. The strategies to limit nosocomial measles infection and spread of measles epidemics are reviewed. Though the measles elimination programmes have been very effective in the Americas, it seems unlikely that they will be equally effective in the rest of the world. Even if eradication should be possible, it might be unwise to stop measles vaccination because the vaccine apparently has beneficial effects and because it would make measles a likely weapon for bio-terrorism. If we are unlikely to get rid of measles and measles vaccine, it might be wise to study further some of the many unanswered questions regarding the long-term effects of measles and measles vaccination.