Vaccination of Saudi Children Against Measles with Edmonston-Zagreb

Abstract

A Abanamy, M Khalil, H Salman, MA Azeem, Vaccination of Saudi Children Against Measles with EdmonstonZagreb. 1992; 12(1): 110-111 To the Editor: Measles vaccine failure due to persistent maternal antibodies is well known, especially in children vaccinated before the age of one year.A recent study has shown that about two thirds of Saudi children at the age of six months have maternal antibodies [1], In Saudi Arabia, the incidence of measles is still high and many cases are reported in children under six months. Measles among vaccinated children is also common [2].In order to protect the young susceptible children against measles, early vaccination at the age of six months was recently introduced by the Ministry of Health. A booster dose is given at the age of 12 months.The use of Edmonston-Zagreb strain in measles vaccine has generated considerable interest because theoretically it may offer better protection to young infants against measles [3]. This strain has not been used before in Saudi Arabia.This study compares the seroconversion rate following vaccination with the current vaccine (Schwartz vaccine) versus Edmonston-Zagreb strain at the age of six months in Saudi children. This is a randomized controlled trial where six month old children were allocated into two groups to receive Edmonston-Zagreb (27 children) or Schwartz measles vaccine (25 children). A control group of 53 children age nine months, which is the usual age of vaccination in Saudi Arabia, was vaccinated using Schwartz vaccine.For children to be vaccinated with Schwartz, we used Rimevax (Smith Kline) live attenuated vaccine. Each dose contains not less than 1000 TCID50 of measles virus. In the Edmonston group, we used Moraten Berna, the attenuated Edmonston-Zagreb virus strain. Each dose from Moraten also contains no less than 1000 TCID50 live measles virus. Both vaccines were tested for potency before starting the trial using Reed and Meunch formula titration for TCID50/dose.In all children, 3 ml blood in a plain tube was taken prior to the vaccination and two months later to measure the measles antibodies in their sera using an indirect flourescent technique using a kit from Virgo Electro-Nucleonic, Inc. A titer of 1/8 or more is considered positive according to the kit. Seroconversion was defined as fourfold rise in the antibody titer in the second sample.Before vaccination, 22 children out of 52 (42.3%) at the age of six months did not have evidence of maternal antibodies compared with 35 of 53 (66%) at nine months of age.After vaccination, 26 of 27 children (96.3%) had seroconversion after vaccination with Edmonston-Zagreb compared with 14 of 25 (56%) vaccinated with Schwartz vaccine. The difference was significant (P = .0018). Eight children from those with seroconversion failure after Schwartz vaccine were followed up to the age of 15 months and another blood sample was taken after giving measles, mumps, and rubella (MMR), all of which showed seroconversion after MMR vaccination. The seroconversion in those vaccinated with Schwartz...

Immunogenicity, effectiveness, and safety of measles vaccination in infants younger than 9 months: a systematic review and meta-analysis

“…The estimated proportion of infants who seroconverted was based on 20 studies25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44 that presented data by age at MCV1 vaccination, ranging from 4 to 8 months. The pooled estimate of the proportion of infants who seroconverted increased from 50% (95% CI 29–71) at age 4 months, to 67% (51–81) at 5 months, 76% (71–82) at 6 months, 72% (56–87) at 7 months, and 85% (69–97) at 8 months (figure 2, appendix pp 15–16).…”

“…Many studies in our search presented results for MCV1 vaccination in a range of ages, rather than by month of vaccination and were therefore not included in our meta-analyses. However, we did additional sensitivity analyses by pooling and comparing seroconversion data from 24 studies presenting data on MCV1 by month of vaccination and age ranges 25, 26, 28, 29, 31, 36, 37, 38, 39, 40, 45, 46, 47, 48, 49. The data presented as age ranges were in accordance with our estimates per month of vaccination (appendix pp 22–23).…”

“…Data from four studies25, 28, 36, 45 allowed us to pool in a meta-analysis head-to-head comparisons of infants vaccinated with the Schwarz MCV strain with those vaccinated with the Edmonston-Zagreb MCV strain at 6 months of age. 18% (95% CI 2–34, p=0·023) more infants seroconverted when vaccinated with Edmonston-Zagreb strain at 6 months than when vaccinated with the Schwarz strain (appendix p 26).…”

Effect of measles vaccination in infants younger than 9 months on the immune response to subsequent measles vaccine doses: a systematic review and meta-analysis

“…On the basis of the 13 articles7, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38 that reported proportions of infants who were seropositive after a two-dose MCV schedule, in which MCV1 was administered before 9 months of age, the pooled proportion of seropositive infants after MCV2 was 98% (95% CI 96–99; figure 2). Five studies7, 27, 28, 36, 39 were meta-analysed for within-study comparisons of the proportion of infants seropositive after MCV2 administration, with MCV1 administered before 9 months of age, with control groups vaccinated at age 9 months or later.…”