Current Vaccination for Measles May Not Be Enough for Elimination

Measles elimination is the absence of endemic measles transmission in a region or other defined geographical area for 12 months or longer.

The current 2-dose measles immunization coverage target of 95% may be the absolute minimum required to provide enough protective immunity in the population to achieve and maintain measles elimination, according to research presented at the European Congress of Clinical Microbiology & Infectious Diseases.

The systematic review examined the efficacy of 2 doses of the measles vaccine in more than 7000 participants from 13 countries. According to the latest data, only 6 countries in the EU/EEG reported 2-dose measles vaccine coverage of 95% or higher, which suggests that elimination of measles in the EU is not certain, according to the investigators.

Measles elimination is the absence of endemic measles transmission in a region or other defined geographical area for 12 months or longer. Because measles spreads easily, an estimated 95% of a population needs to be vaccinated with 2 doses of the measles-containing vaccine (MCV2) every year to achieve full protection and prevent further outbreaks, according to the study.

In the current elimination strategy, 2 doses of measles are assumed to be approximately 96% effective in preventing the virus, which makes an estimated 91.5% of the population immune to the disease. However, the estimates of MCV2 vaccine efficacy have not been properly combined to determine whether they are high enough to achieve elimination.

The research team searched through all observational studies that were published in English, German, Dutch, and Spanish, that reported on vaccine efficacy of MCV2 through April 2021. The final analysis included 33 peer-reviewed articles from an initial supply of 430. In the analysis, 21 studies were compared to the risk of measles in individuals aged 9 months or older without immunodeficiency who had received MCV2 to those who had not been vaccinated.

The average MCV2 efficacy was 96.4% in the analysis of the general population under real world conditions, and age, location, and study design did not appear to have an impact on vaccine efficacy, according to the study investigators.

The study authors noted some limitations, including the review being mainly observational studies included from Europe and North America. Additionally, the studies did not provide data on people older than 23 years of age, which may limit the conclusions that could be drawn.

REFERENCE

Current measles vaccination targets may not be enough to achieve elimination. EurekAlert! April 6, 2022. Accessed April 11, 2022. https://www.eurekalert.org/news-releases/948817