Efficacy of measles vaccine during the 1993 measles epidemic in Korea

The effect of time since measles vaccination and age at first dose on measles vaccine effectiveness - A systematic review

BACKGROUND

In settings where measles has been eliminated, vaccine-derived immunity may in theory wane more rapidly due to a lack of immune boosting by circulating measles virus. We aimed to assess whether measles vaccine effectiveness (VE) waned over time, and if so, whether differentially in measles-eliminated and measles-endemic settings.

METHODS

We performed a systematic literature review of studies that reported VE and time since vaccination with measles-containing vaccine (MCV). We extracted information on case definition (clinical symptoms and/or laboratory diagnosis), method of vaccination status ascertainment (medical record or vaccine registry), as well as any biases which may have arisen from cold chain issues and a lack of an age at first dose of MCV. We then used linear regression to evaluate VE as a function of age at first dose of MCV and time since MCV.

RESULTS

After screening 14,782 citations, we identified three full-text articles from measles-eliminated settings and 33 articles from measles-endemic settings. In elimination settings, two-dose VE estimates increased as age at first dose of MCV increased and decreased as time since MCV increased; however, the small number of studies available limited interpretation. In measles-endemic settings, one-dose VE increased by 1.5% (95% CI 0.5, 2.5) for every month increase in age at first dose of MCV. We found no evidence of waning VE in endemic settings.

CONCLUSIONS

The paucity of data from measles-eliminated settings indicates that additional studies and approaches (such as studies using proxies including laboratory correlates of protection) are needed to answer the question of whether VE in measles-eliminated settings wanes. Age at first dose of MCV was the most important factor in determining VE. More VE studies need to be conducted in elimination settings, and standards should be developed for information collected and reported in such studies.

The changing epidemiology of hospitalized pediatric patients in three measles outbreaks

OBJECTIVES

To assess the demographic and clinical findings of measles patients during three epidemics from 1989 to 2001.

METHODS

A total 520 medical records of measles patients were analyzed retrospectively and divided into three groups; those who were admitted during 1989-1990 (group I, 116 patients), those admitted during 1993-1994 (group II, 127 patients), and those admitted during 2000-2001 (group III, 277 patients).

RESULTS

For the age distribution, there was no difference in the proportion of < 2 years of age (61%, 58% and 57%, respectively) for the three groups. However, in each outbreak, there were significant differences in the distribution of > or = 2 years children who had mostly received one-dose measles-mumps-rubella (MMR) vaccination. The age distribution had changed with a significant increase in older children in subsequent outbreaks. In the last 2000-2001 outbreak, there was a pattern for increased attack rates with increasing interval since the initial vaccination. There was no statistical difference between the three groups in gender ratio, MMR vaccination rate in > or = 2 years of age, duration of fever, and complications. No difference was found in all the clinical and laboratory parameters between the anti-measles IgM antibody negative patients and the positive patients.

CONCLUSIONS

The age distribution of admitted children with measles in each outbreak has changed over time since the introduction of one-dose MMR vaccination. This finding suggests that the secondary vaccine failure may have played a large role in the last measles outbreak.

Effectiveness of measles vaccination after household exposure during a measles outbreak: a household contact study in Coburg, Bavaria

BACKGROUND

A measles outbreak was recently observed in Coburg, Bavaria, in a population with vaccination rates of 76.5% in 5- to 6-year-old children in the years preceding the outbreak. Only a small proportion of children had received 2 vaccinations against measles. Vaccine effectiveness is estimated in a household contact study and also by a screening method.

METHODS

A household contact study was conducted in families with at least 1 measles case by standardized computer-assisted telephone interviews to assess secondary attack rate and to estimate vaccine effectiveness. Vaccine effectiveness was also estimated with Farrington's screening method with information from school entry examinations and from questionnaires of confirmed measles cases in the Coburg outbreak.

RESULTS

Thirty-eight children were primary cases. Of their contacts, 20 children were included in the study as secondary cases (1 vaccinated), and 23 children were contacts who did not develop measles (12 vaccinated once and 4 vaccinated twice), resulting in a vaccine effectiveness of 90% (95% confidence interval, 35-97%) for one vaccine dose. The proportion of the population vaccinated reached 81.5% during the outbreak and the proportion of the cases vaccinated was 10.9%, resulting in a vaccine effectiveness estimated using the screening method of 97.2% (95% confidence interval, 95.7-98.3%).

CONCLUSIONS

With the use of 2 approaches to estimate the effectiveness of measles vaccination, a consistently high vaccine effectiveness of 90% or above was shown during a measles outbreak in Western Europe.