A previous measles outbreak investigation in a high school in Quebec, Canada identified 2-dose vaccine effectiveness of 94%. The risk of measles in 2-dose recipients was significantly higher (2–4 times) when measles vaccine was first administered at 12 versus ≥15 months of age, with no significant effect of the age at second dose. Generalizability of this association was also assessed in the expanded provincial data set of notified cases.
This matched case–control study included only 2-dose recipients. All confirmed (laboratory or epidemiologically linked) cases in patients aged 5 to 17 years were included. Each case was matched to 5 controls.
A total of 102 cases and 510 controls were included; 89% of cases were in patients 13 to 17 years old. When the first dose was administered at 12 to 13 months compared with ≥15 months of age, the risk of measles in participants outside the outbreak school was 6 times higher (95% confidence interval, 1.33–29.3) and was 5.2 times higher (95% confidence interval, 1.91–14.3) in the pooled estimate (participants from the outbreak school + outside that school).
A significantly greater risk of measles among 2-dose recipients whose first dose was given at 12 to 13 months rather than ≥15 months of age is confirmed in the larger Quebec data set. The mechanism remains unknown, but vaccine failures in 2-dose recipients could have substantial implications for measles elimination efforts through 2-dose vaccination. The optimal age at first dose may warrant additional evaluation.
I read this article with interest as somebody working in measles surveillance in a country (India) which has now signed the measles elimination pledge. The implications of this can be enormous globally. In India measles immunization started in the 1980s and the current cohort of mothers in states with good immunization got their antibodies probably from vaccine rather than the disease. If we were to adopt a later schedule this would give rise to cases in the 6 months to 1 year age group. Since last year children get two MCVs at 10 months and 18 months. It seems they might get waning immunity over a period of time if the same dynamics operate. Clearly seroprevalence studies among all age groups should precede formulation of a measles elimination strategy anywhere in the world.
Dr Santhosh Rajagopal
Surveillance Medical Officer
WHO Country Office for India - NPSP
Madurai, Tamilnadu, India
Conflict of Interest:
None declared
To the editor:
We have read Dr.Defay's article entitled "Measles in Children Vaccinated With 2 Dose of MMR"interestingly, since we also have suggestive clinical data. In Japan, measles and rubella combined (MR) vaccines are administered to children when they are 1 year old and for 1 year until their elementary school entrance. Some authorities recommend that the first MR vaccine should be administered to children on their first birthday as a birthday present. In 2012, we compared the measles virus antibodies (EIA) in 10 children who had been administered MR vaccine as a birthday present between 12 and 13 months and those in 22 children administered over 15 months at the age of 18 months. While the former were dotted on 8.3~59.7(22.59+-16.13), the latter were 13.3~93.4(49.88+-25.68). Above all, 3 children in the former group proved under 10.0. Moreover a boy, whose 23 year-old mother had suffered from measles at the age of 2 and had been administered MR vaccine at the age of 20, showed primary vaccine failure (under 2.0). The recommendation had been reasonable in 1990s, when patients with measles amounted to more than 100,000 per year all over Japan. However registered number of patients with measles has diminished to under 1,000 per year. In this environment, we don't need to administer MR vaccine to children on their first birthday. We also pay attention to mother's antibody titers. At least one-tenth mothers suffered from measles in 1980~1990s. Moreover many younger mothers have been administered MR vaccine at the age of 18~20 at their residential area or their college. These facts mean some mothers have high titer of antibody to measles and their children seem to have residual maternal measles antibody for longer duration. These observation may prove our findings and suggest one of solutions to Defay's question. We also propose the first MR or MMR vaccine should be administered at >=15 months of age.
Conflict of Interest:
None declared