Related Experiment Videos
Serologic status and measles attack rates among vaccinated and unvaccinated children in rural Senegal
1Unité de Recherche sur les Maladies Infectieuses et Parasitaires, ORSTOM, Dakar, Senegal.
Insights
Measles vaccine efficacy reached 90% in a Senegal trial. Even without detectable antibodies, vaccinated children showed significant protection against measles compared to unvaccinated peers.
Area of Science:
- * Immunology and Infectious Diseases
- * Vaccinology and Public Health
Background:
- * Measles remains a significant public health concern, particularly in regions with lower vaccination coverage.
- * Assessing vaccine effectiveness and understanding antibody correlates of protection are crucial for disease control.
Purpose of the Study:
- * To evaluate measles vaccine efficacy in a rural African setting.
- * To compare the predictive value of hemagglutinin-inhibiting (HI) and plaque neutralizing (PN) antibody assays for measles susceptibility and protection.
- * To determine the protective antibody threshold against measles.
Main Methods:
- * A measles vaccine trial was conducted in Senegal involving 228 vaccinated and 313 unvaccinated children over 12 months old.
- * Antibody status was assessed within 10 days of measles exposure.
- * Clinical measles diagnosis was confirmed, and vaccine efficacy was calculated.
Main Results:
- * Overall vaccine efficacy was 90% (95% CI, 83-94%).
- * Both HI and PN assays demonstrated equal efficiency in predicting protection.
- * Vaccinated children without detectable antibodies still showed significant protection (43-49% efficacy) compared to unvaccinated children.
- * Attack rates were substantially lower in children with HI or PN titers above 125 mIU.
Conclusions:
- * The measles vaccine is highly effective in the studied population.
- * HI and PN antibody assays are reliable tools for assessing measles immunity.
- * An antibody titer of approximately 120-125 mIU may represent a protective threshold, though some seronegative vaccinated individuals retain protection.
Abstract:
During a measles vaccine trial in a rural area of Senegal, antibody status was examined within 10 days of exposure for 228 previously vaccinated and 313 unvaccinated children more than 12 months old who were exposed to measles at home. Thirty-six percent of the children developed clinical measles, the clinical diagnosis being confirmed for 135 of the 137 children from whom 2 blood samples were collected. Vaccine efficacy was 90% (95% confidence interval, 83 to 94%). The hemagglutinin-inhibiting antibodies (HI) or plaque neutralizing antibodies (PN) assays were equally efficient in predicting susceptibility and protection against measles. Vaccinated children who had no detectable HI or PN antibodies at exposure had significant protection against measles compared with seronegative unvaccinated children (HI vaccine efficacy, 49% (95% confidence interval, 21 to 68%); PN vaccine efficacy, 43% (95% confidence interval, 12 to 62%)). The attack rate was high for children with a titer of 40 to 125 mIU) 67% (4 of 6) of those with a positive hemagglutinin-inhibiting antibody test and 36% (13 of 36) of those with a positive PN test developed measles. Attack rates among children with HI or PN titers above 125 mIU were 2% (6 of 295) and 3% (7 of 258), respectively. Because titers of < or = 120 mIU have been found to offer little protection in another study, this antibody level may be the best screening value for assessing susceptibility and protection against measles. However, it should be noted that many seronegative vaccinated children are protected against measles infection.